Marco Overhaus

A Matter of Credibility

Conventional and Nuclear Security Commitments of the United States in Europe

SWP Research Paper 2019/RP 10, August 2019

doi:10.18449/2019RP10

Dr. Marco Overhaus is a Senior Associate in the Americas Division at SWP.

US President Donald Trump has cast doubt on his country’s security commitments within NATO by his “America First” programme and his verbal attacks on the Alliance. This affects both conventional reassurance, i.e. pledges to allies backed by non-nuclear military means, and nuclear reassurance.

Beyond the “Trump factor”, the costs and risks associated with these security commitments have increased from Washington’s perspective. The reasons are the expansion of the Alliance territory through its eastern enlargement, the modernisation of the Russian military, and the end of the US’s undisputed military supremacy. Nevertheless, during the Trump administration, the US has not reduced but increased its financial and military contributions to the reassurance of its allies.

Uncertainties about the US’s role in NATO have led to deepening rifts in Europe. On one side are the European allies that are striving for a higher degree of “strategic autonomy” from Washington, and on the other those who want to lean even more on the US as a protecting power. From the perspective of many eastern NATO states, American security promises are more credible than potential European alternatives, even during the Trump administration.

The credibility of American security commitments is a multifaceted issue that cannot be reduced to statements by the US President. European NATO states consider and weight the underlying factors differently. Political deci-sion-makers, not least in Germany, must be alert to these differences for the sake of political cohesion in the EU and NATO.

Issues and Recommendations

With his “America First” programme and verbal at­tacks on NATO, US President Donald Trump has cast significant doubt on the credibility of American secu­rity commitments within the Alliance. This applies to both its conventional and nuclear aspects. For the purposes of this research paper, “conventional reas­surance” is understood as those pledges to allies that are underpinned by non-nuclear military means, and “nuclear reassurance” as the commitments underpinned by nuclear military means.

Article 5 of the Washington Treaty postulates that member states shall regard an attack on one as an at­tack on all. This political commitment is underpinned by the presence of US troops and military capabilities in Europe. For decades, Alliance members therefore shared the assumption that in the event of a crisis or war, Washington would assist its NATO partners with conventional and, in extreme situations, nuclear weapons. The USA was the only NATO state with the political will and capabilities to guarantee the secu­rity of the entire Alliance territory.

How credible are American security commitments in times of Trump? In the German political debate doubts are gaining ground. This is why there is in­creasing discussion about how Europe can become more independent of Washington in terms of security policy. Federal Chancellor Angela Merkel said in May 2017 that the “times when we could completely rely on others [...] are largely over”. In France, arguing for European strategic autonomy has a long tradition.

By contrast, some eastern NATO states, primarily Poland, the Baltic states and Romania, have been relying even more heavily on America as a protecting power since Trump took office. Yet again other coun­tries, such as the Czech Republic and Hungary, are making efforts to move closer to Russia, at least in some policy fields such as energy. Obviously, European states view American security and defence policy very differently. These divergent perspectives are a prob­lem for cohesion both in the European Union (EU) and in NATO.

This study focuses on three factors that underlie the credibility of American reassurance:

  • 1. the political support for alliance commitments of the relevant domestic actors in the USA;

  • 2. the development of the security environment, in particular the military (im-) balances in specific parts of Europe; and

  • 3. the concrete financial and military contributions of the USA towards underpinning its security com­mitments in the light of the changing security landscape.

European allies assess and weight these three factors differently based on their respective security and threat perceptions. This study confines itself to examining the perspectives of several Eastern NATO countries that feel particularly exposed to Russia.

Doubts about the credibility of America’s Alliance commitments arise above all with regard to the first two factors: political support within the USA and the development of the security environment. The third factor, the concrete financial and military contributions of the USA to European security, thus gains con­siderably in importance.

Overall, German and European actors have very few opportunities to directly influence the credibility of American reassurance. The most feasible way to achieve this is to politically strengthen those forces in the US administration and Congress who advocate the continued integration of the US into the Alliance.

The basic prerequisite for this political support is reliable financial and military contributions from Germany and other European states to the joint task of collective defence. If European partners are unable to provide at least some of the critical conventional capabilities for this mission, NATO supporters in the US will have an increasingly poor foundation for their arguments.

As regards nuclear weapons, Europe’s ability to achieve credible reassurance on its own without the US is even more limited than with conventional capabilities. The majority of European NATO states, including Germany, have relatively little interest in nuclear issues. Most of the states that regard nuclear deterrence as still important for national defence policy see no alternative to America’s promises of protection, even under the Trump administration.

For the eastern NATO states, the credibility of American nuclear reassurance is based on a political and strategic understanding of the importance of these weapons. The decisive factors are therefore that the USA politically commits itself to extended nuclear deterrence – as indicated in its current nuclear strategy of 2018 – and that, under Trump, neither friend nor foe can assess with absolute cer­tainty how the USA would react in the event of a nuclear crisis.

Yet issues of specific nuclear capability – i.e. how many weapons are stationed on which carrier systems in Europe, and what their explosive yield is – are of little relevance to the eastern NATO states. Debates on these issues therefore risk splitting NATO rather than contributing to the credibility of reassurance.

In view of the domestic developments in the USA, of which President Trump is a symptom rather than a cause, it may be true that Europe should be striving for greater defence autonomy from the USA. Security commitments that European states make to each other within the framework of a European Defence Union must be measured by the same standards that have applied to the USA for more than seven decades. In order to be credible, reciprocal security pledges made by European states must therefore be backed by strong political will in their capitals as well as suffi­cient financial and military resources. Above all, these security pledges must be seen as credible by all states that are part of the European integration project within the EU and NATO.

The Credibility of Security Commitments

Definition and Criteria

This study focuses on America’s security commitments to its NATO allies, i.e. the issue of reassurance. This must be distinguished from deterrence, which addresses the potential opponents of an alliance. The two concepts are closely linked, but not identical.

There is little doubt that the US would defend its security when countering threats to its own territory. Credibility becomes problematic in security pledges to partners and allies. According to Thomas Schelling, the difference “between the national homeland and everything ’ abroad’ is the difference between threats that are inherently credible, even if unspoken, and the threats that have to be made credible.1

Although a great deal of academic literature has dealt with the question of the credibility of US secu­rity and defence policy – especially with regard to nuclear deterrence – the term “credibility” remains remarkably unclear. This may be due to the fact that since credibility is a largely subjective phenomenon, it is difficult to grasp. Whether or not the USA is credible is ultimately decided by the addressees of American policy – both its allies and its opponents.2

The credibility of security commitments and reassurance is understood in this study as the well-founded and comprehensible expectation of European NATO partners that Washington will honour its security pledges made within the framework of the Alliance. These expectations are well-founded and comprehensible in as the sense that they are based on an analysis of US interests and a cost-benefit calculus of these commitments for Washington. This distinguishes credibility from other concepts such as “trust” or “reputation”. Trust is based on social and personal ties; reputation on the past behaviour of states, groups or individuals and the expectation that they will con­tinue to behave in the same or similar manner in the future.3

Credibility depends on three factors: political will, the military balance of power and specific military contributions.

Three factors can be derived from this definition of credibility so as to assess and classify it, although not exactly “measure” it. The first is the political will in the relevant centres of power within the American system of government. To what extent do US security commitments to NATO partners enjoy political sup­port in the White House, the administrative apparatus and Congress? Is the security of European NATO countries defined as a significant US interest for which America would be willing, in the event of a crisis or armed conflict, to assume the costs and risks of using military force?

The second factor for assessing credibility is the changes in the European security environment, mainly the development of military balances and capabilities. These developments determine the costs and risks that Washington bears for its NATO com­mitments. The greater the imbalance to the detriment of the US and NATO, the greater the risk and likeli­hood that, in the event of a conflict, the security pledges cannot be honoured – and therefore the lower the pledges’ credibility.

The third factor is the financial, military and operational capabilities with which the USA buttresses its security commitments. The larger these con­tri­butions are, and the more specifically tailored they are to the security situation in Europe, the more credible the security pledges appear. Such specific contributions underline Washington’s willingness to translate words into deeds and to provide actual resources. The probability that the security of Euro­pean NATO partners can be successfully defended in the event of a crisis or war also increases.

These three factors, on which the credibility of US security commitments is based, are considered and weighted by NATO allies through the lenses of their respective national experiences and security perceptions.

Reassurance: the Conventional and Nuclear Aspects

There are important differences between the conventional and the nuclear dimensions of security reas­surances.

The threat or actual use of nuclear weapons would mean crossing a political and psychological threshold. In such a situation controlling escalation becomes considerably more difficult or even impossible. The risk of a comprehensive nuclear war, which would be tantamount to the complete destruction of the parties involved, would move within reach. This also applies when, in a crisis situation, “only” non-strategic nucle­ar weapons4 are used to begin with.

Against this background, the nuclear reassurance of the USA towards its NATO partners is always in­herently lacking credibility. Why should the US risk Washington being destroyed to guarantee the safety of Berlin or Tallinn? Nevertheless, the USA still under­pins its security commitments to more than 30 coun­tries across the globe – NATO members, South Korea, Japan and Australia – with nuclear weapons.5

There are two alternative views in the research literature as to why nuclear commitments can still be credible.6 According to the political and strategic per­spective, nuclear pledges or threats are essentially a “competition in risk-taking”.7 The nuclear powers take institutional or military steps that increase the risk of escalation, even to the point of nuclear war, without either side being able to fully control the process. For example, they can station troops in sensi­tive regions as “trip wires” or set up automatic action-response mechanisms.8 According to Schelling, it is the strategic weapons that constitute the risk of mu­tual annihilation. In this sense, however, all nuclear weapons are “strategic”.9 From this perspective, the specific nuclear capability – i.e. the number of nu­clear weapons, their explosive yield, delivery systems and deployment sites – is of secondary importance.

The second view of the credibility of nuclear commitments is more “operational” because its focus is more on the possibility that deterrence may fail. If it were possible, or at least conceivable, to limit the damage that a regional war in Europe or Asia, in­cluding a nuclear war, could do to the USA by means of “flexible” options – especially bombs with lower explosive yield – the credibility problem would de­crease. In that case America, as a nuclear guarantor power, would have the prospect of not being de­stroyed itself in the event of a conflict. The threat against one’s opponent and the nuclear reassurance of one’s own Alliance partners would thus be more credible. That, at any rate, is the logic that is also re­flected in the Trump administration’s nuclear strategy of 2018. From this “operational” perspective, the con­crete design of the US nuclear capability is of great importance for the credibility of nuclear reassurance vis-à-vis its allies.

The ambivalence of political intentions can increase the credibility of nuclear reassurance.

The following applies to both approaches: all deci­sion-making processes during a nuclear crisis point towards the US president. The classical theory of nuclear deterrence postulates that the ambivalence of political intentions can even increase the credibility of threats.10 In other words, even if it is unlikely that the US president – and especially this president – would actually be prepared to use nuclear weapons to defend European NATO allies, the consequences for allies and opponents alike would be grave. The un­predictability attributed to President Trump may therefore prove to be a strength.

Wars that are fought with conventional weapons are – at least in the eyes of political decision-makers – more controllable and scalable11 than nuclear scenarios. The principle of conventional reassurance today has not fundamentally changed since the Cold War: by pre-stationing armed forces, the allies in­volved signal their readiness to be drawn into the military conflict at an early stage if another partner is attacked. In a conflict constellation between two nuclear powers, the purpose of conventional defence is either to prevent fait-accompli scenarios12 – i.e. a rapid territorial conquest through surprise attacks – or to raise the political and military costs for the attacker. It can also be used to raise the threshold for the use of nuclear weapons.

In the event of a war fought with conventional weapons, too, the US president ultimately makes all the essential decisions himself. However, since the use of conventional means is easier to control and scale compared to the use of nuclear weapons, other decision-making centres in Washington, notably Congress, have more say. In the multilateral context of NATO, this means that consensus-building in the joint Alliance institutions becomes very important during a crisis. When used positively, this can favour de-escalation, but it can also lead to a political block­ade in the NATO Council and thus to the inability to act.

Whether or not promises or threats which are underpinned by conventional means are credible fundamentally lies in the design of military capabilities and the regional balance of power. Nuclear weap­ons, due to their great destructive power, leave much less room for interpretation with regard to their effec­tiveness. Conventional means, on the other hand, give the potential opponent more opportunities to neutralise or mitigate their effect through appropriate defensive measures.13 In sum, the credibility of nucle­ar reassurance is based on a “competition of risk taking”, while the credibility of conventional reassur­ance primarily rests on a competition of capabilities.14

Domestic Support for Alliance Commitments in the United States

The political will of key US actors to honor the country’s NATO commitments is the first factor by which partners assess the credibility of US security reassurances. The more unanimous and emphatic this willingness, the greater the credibility.

The broad, bi-partisan support for the integration of the United States into NATO has been a fundamental constant of American security policy for almost seven decades after the founding of the Alliance in 1949. From an American perspective, NATO was the central security policy instrument to prevent the Soviet Union from dominating Europe.

Thus, it was irrelevant whether a Democratic or Republican administration sat in the White House. Of course, there were still domestic debates. Congress repeatedly called for more balanced transatlantic burden-sharing, which in several cases went as far as proposals to reduce US troops in Europe.15 During the Vietnam War, the prevailing consensus on the hege­mony of the USA collapsed. This consensus had im­plied that America was ready for “almost limitless engagement and commitment”16 in security and de­fence policy to contain the influence of the Soviet Union. While support for proxy wars in the “Third World” declined, this did not apply to America’s security and defence role in Europe.17 Despite all controversies, respective US administrations never questioned America’s security commitments within NATO.

Since the election of Trump, the question of whether the USA could revoke its Alliance commitments has been raised for the first time.

Even after the collapse of the Soviet Union, strength­ening the Alliance remained a central con­cern to Washington, albeit under changed circumstances. Containing Moscow receded into the back­ground as NATO’s raison d’être, but the Alliance now served other interests: crisis management in the West­ern Balkans, the fight against international terrorism and, of course, the global power projection of the USA. After the fall of the Iron Curtain, American reassurance towards its Alliance partners was based on a much smaller US military footprint in Europe.

Following the Russian annexation of Crimea in 2014, President Obama assured eastern NATO part­ners that the US would defend “every single ally” be­cause “the defence of Tallinn and Riga and Vilnius is just as important as the defense of Berlin and Paris and London”.18

Since Donald Trump’s election to the White House, the question of whether Washington could end its decades-long policy of Alliance integration and thus revoke its promises of protection for its allies has been raised seriously for the first time.

President Trump

Donald Trump, as presidential candidate and later as president, has made contradictory remarks about America’s security commitments. Overall, however, he has adopted a distanced and sometimes even hostile stance towards the US’s security alliances in Europe and Asia. He has a transactional understanding of these alliances, i.e. from his point of view they are comparable to an insurance policy for which the partners have to make a financial contribution. Otherwise the insurance cover expires.19 This contra­dicts the political understanding on which American NATO policy has been based for decades: alliance commitments, while not unconditional, are based first and foremost on shared interests and values.

As a candidate for the White House, Trump wanted to make US support for allies in both Europe and Asia conditional on their respective defence contributions.20 He also explicitly questioned the nuclear com­ponent of American reassurance vis-à-vis the Asian allies. In fact he suggested to Japan and South Korea that they should obtain their own nuclear weapons.21 This would be a radical departure from decades of US policy, which regarded extended nuclear deterrence22 as an essential instrument for the non-proliferation of nuclear weapons.

As president, Trump eventually committed to Article 5 of the NATO Treaty, albeit hesitatingly. How­ever, he once again distanced himself from it during the NATO summit in July 2018. According to diplo­mats, behind closed doors he threatened the assembled NATO leaders with Washington going its own way on defence issues in the future if the other NATO countries did not quickly spend more money on their defence.23 Shortly afterwards, in an interview with the television channel Fox News, he sowed doubts as to whether America would defend the newest NATO accession state, Montenegro, in the event of an attack, because the people there were “aggressive” and could drag the USA into the Third World War.24 According to a New York Times report, in 2018 Trump repeatedly told advisors that he wanted to withdraw the USA from NATO.25 Publicly, however, the president said Washington was “100 percent” behind the Alliance.26

What is truly explosive about Trump’s remarks on NATO is not that he is particularly insistent or less diplomatic in demanding more defence burden-sharing from European Allies (a demand shared by many European and American commentators). Nor is it the fact that the president is linking economic issues (e.g. the EU’s trade surplus with the USA) and defence policy issues. During the Cold War, John F. Kennedy and other US presidents also pointed to balance of payments problems in connection with the presence of US troops overseas, and demanded economic compensation from Germany.

The stand-out factor is that Trump is the first US president to distance himself from the US security commitments to NATO allies and to attach specific conditions to it. This is a move away from the prin­ciple that the security of NATO territory is indivisible, which had previously been sacrosanct in Washington. Trump’s repeated verbal attacks on NATO (“obsolete”, “as bad as NAFTA [North American Free Trade Agree­ment]”27, etc.) illustrate this sea change.

US policy towards NATO during Trump’s first two-and-a-half years in office has contributed to the dis­trust felt in some European capitals at statements made by other high-ranking US officials. US Vice Pre­sident Mike Pence said at the Munich Security Con­ference in February 2019 that the US “cannot ensure the defense of the West if our allies grow dependent on the East”.28 Particularly in Germany, this was seen as a barely veiled threat regarding the dispute over the Nord Stream 2 gas pipeline under construction between Germany and Russia. The fact that at the be­ginning of his speech Pence unequivocally reaffirmed the US commitments to mutual defence with­in NATO did not change this perception.

The Administration

The term “administration” is often used in connection with American government policy. This is a collective term which in the area of foreign and security affairs includes the president’s closest advisory circle (nation­al security advisor, foreign and defence ministers, leading military personnel), the presidential bureaucracy (especially the National Security Council), and the ministerial bureaucracies (foreign and defence ministries). The administration selects and structures information, and formulates options, and is therefore essential for the preparation and implementation of the president’s decisions.

Numerous media reports and recently published books by investigative journalists29 or former adminis­trative staff paint the picture of a White House work­ing chaotically for long stretches, with staff devoting a considerable part of their energy to con­trolling their president or even actively countering his agenda. Sometimes there is even talk of a “dual presidency” in which the administration pursues an agenda that is diametrically opposed to the president’s.30

As far as US security and defence policy in NATO is concerned, this characterisation is quite accurate: all three consecutive National Security Advisors – Michael Flynn, Herbert Raymond McMaster and John Bolton – have tried to keep their president from his verbal attacks on NATO. Former Secretary of State Rex Tillerson, together with Flynn, has advocated for Montenegro’s accession to NATO and thus for an ex­tension of American security pledges to the country, both in front of Trump and the Senate.31

The view that the USA is a global leading power is still firmly anchored in Washington’s administrative apparatus.

Even Bolton, who is watched like a hawk in Europe because of his earlier remarks on possible military strikes against North Korea and Iran, and his hostility to multilateralism and the United Nations, worked with US Secretary of State Mike Pompeo to prevent a failure of the NATO summit in July 2018. Both urged that the summit declaration be finalised long before the meeting, thus removing it from Trump’s notice as far as possible.32 In both the US and Europe, Defence Secretary James Mattis was regarded as the most im­portant NATO supporter within the Trump administration until he resigned in early January 2019. His successor, Mark Esper, has so far also expressed his strong support for NATO and other US alliances.

Below the leadership level of advisors and cabinet members, the administration is also essentially char­acterised by a foreign and security policy elite within the institutions and ministries. This elite has been habituated over seven decades to the role of the USA as a leading power and is “internationalist to its core”,33 including the understanding that the USA bases its international leadership role essentially on alliances. Above all, the US Department of Defence and the military appear in the administrative appara­tus as advocates for the US-led alliances and are there­fore of great relevance for underpinning security commitments to NATO partners.

Even though the Pentagon and military are not a monolithic bloc, the civilian and military leadership in the Department of Defence nevertheless supports firmly anchoring the United States in the Alliance as well as America’s continued military presence in Europe. Since the Russian annexation of Crimea in 2014, the US forces’ European Command (EUCOM) and its commander-in-chief – who are presumably not devoid of institutional self-interest – have advo­cated strengthening American contributions to NATO reassurance and have intensively promoted this in Congress.34 Former EUCOM chief General Curtis Scaparrotti even pleaded in 2018 for more US troops to be permanently stationed in Europe.35

Beyond its European command the American mili­tary continues to have a great interest in integration into NATO. Since 2015, if not before (in other words, under the Obama administration) the security and defence policy priorities within the military appara­tus have once again shifted towards great power rivalries.36 The focus is on Russia and China. At the same time, other tasks of the military, such as crisis management, counterinsurgency and anti-terrorism, have receded into the background. During this shift of focus, NATO, like other traditional alliances of the United States, has gained in importance from the point of view of the military.

The unambiguous support of the administrative apparatus for NATO and for America’s security com­mitments within the Alliance is also reflected in the strategic policy documents. These bear the hallmark of the national security bureaucracy. The 2017 National Security Strategy (NSS), for instance, states that the United States sees “the invaluable advantages that our strong relationships with allies and partners deliver” and that it “remains committed to Article V of the Washington Treaty [on collective defence]”.37 The 2018 National Defense Strategy contains an identical commitment to America’s alliance pledges, while at the same time exhorting NATO partners to implement the higher defence spending that they themselves have pledged.38

Several passages of the Nuclear Posture Review (NPR) of 2018 commit the USA to extended nuclear deter­rence, i.e. to underpinning American promises of protection to its allies with nuclear weapons.39 Despite Trump’s fundamentally disapproving stance towards multilateral institutions, the USA still seems to adhere to joint nuclear consultations and planning under his presidency.40 Since the establishment of the Nuclear Planning Group in the 1960s, these have been an essential pillar of the credibility of US nucle­ar reassurance. Finally, in line with the Missile Defense Review (MDR) published in 2019, US missile defence capabilities are intended not only to protect American territory, but also to reassure allies and partners.41

Congress

The legislative branch in the USA has a number of long levers in security and defence policy vis-à-vis the president and administration. Congress has the sole right to establish and maintain armed forces, and to declare war. It also adopts sanctions legislation and controls the budget.

In Congress, there has traditionally been bi-parti­­san support for NATO. The Russian annexation of the Crimean peninsula and the war in eastern Ukraine have increased rather than decreased this support. However, this also means that US alliance policy is associated with an increasingly confrontational atti­tude towards Russia. This can be seen, for example, during the annual hearings on the US Armed Forces’ European Command in the relevant committees of the House of Representatives and the Senate.

US military contributions to the conventional re­assurance of NATO partners and their financial back­ing in the European Deterrence Initiative (EDI) have received almost unanimous support in both political camps.42 Most debates focus on the need for an effec­tive deterrent against Moscow.43 Members of Congress from both parties were also receptive to the idea of stationing American troops permanently – i.e. not just on a rotation basis – on the territory of eastern NATO allies. The National Defense Authorization Act for 2019 mandated the Pentagon to examine this option.44

Positions within Congress regarding the nuclear component of reassurance are less consensual. How­ever, there is no dispute about the extended nuclear deterrence per se, only about the design of the US nuclear arsenal. While the modernisation of the stra­tegic “triad” of intercontinental missiles, bombers and submarines fundamentally receives support across party lines in Congress,45 the Democrats are opposed to the procurement of new nuclear weapons with low explosive yield.46 In their view, by lowering the thresh­old for using nuclear arms, these weapons increase the risk of nuclear war rather than strengthening deterrence against other nuclear powers.

There are only a few scattered voices in Congress that question the principle of the North Atlantic Alliance or its basic policies. The independent Senator Angus King, for example, referred to the risks that a US military build-up in Central Eastern Europe might entail for relations with Russia.47 Republican senators Mike Lee and Rand Paul have spoken out against the inclusion of more member states in the Alliance. As long as the US carries the lion’s share of NATO’s defence burden, Lee said, “[w]e cannot and should not consider expanding these commitments”; the USA should not pre-emptively commit itself to waging “everyone else’s wars”.48

Given Trump’s hostile statements on NATO, Congress has repeatedly taken the initiative to demonstrate US solidarity with its allies. In February 2018, Senators Thom Tillis (a Republican) and Jeanne Sha­heen (a Democrat) revived the Senate NATO Observer Group, which will act as a link between the Senate and the Alliance to strengthen transatlantic relations. The group consists of ten senators in key positions, in­cluding the chairman and co-chairman of the Foreign Affairs Committee.49

Just before the NATO summit in Brussels in July 2018, both houses of Congress – the House of Repre­sentatives unanimously, and the Senate with a clear majority of 97 votes to 2 – adopted their own (non-binding) resolutions expressing their support for the Atlantic Alliance.50

After the mid-term elections to Congress in November 2018, which gave the Democrats a majority in the House of Representatives, there are no signs that cross-party solidarity with NATO is weakening. With a large majority of 357 votes in favour and 22 against, the new House of Representatives has passed a bill that excludes the use of budgetary resources to with­draw from the Alliance.51 In the Senate, which re­mains dominated by the Republicans, a group of sen­ators from both parties introduced a law that pro­vides for new sanctions against Russia, as well as high legis­lative hurdles for a possible US withdrawal from NATO.52 The invitation to NATO Secretary General Jens Stoltenberg to address both chambers of the US Congress in April 2019 on the occasion of the 70th anniversary of the signing of the Washington Treaty also demonstrates the broad, cross-party support for the Alliance.53

This does not mean that Congress views NATO wholly uncritically. Both senators and representatives keep calling for more balanced military burden-sharing. Unlike Trump, however, they do not posit the issue of military burden-sharing as a condition for US security commitments.

Doubts about US Credibility

Security and defence relations between the United States and its allies take place on several levels: between politicians, diplomats, military personnel, parliamentarians and civil-society representatives. Any perceptions of the credibility of security pledges are therefore not shaped by just one person. Yet the solid support for NATO in the administration and Congress cannot hide the fact that President Trump’s statements have raised serious doubts about these commitments.

NATO enjoys broad, bi-partisan support in Congress. In the event of a crisis, however, the president is the one person who matters.

In crisis situations, all essential security and defence decisions converge on the White House. Nevertheless, there are many indications that even during “normal functioning”, formal decision-making processes in the Trump administration can come to a standstill or can easily be circumvented by the president. Access to the president is made difficult for close advisors and even more so for senior officials. This became clear, for ex­ample, at the first bilateral meeting between Trump and Russian President Vladimir Putin in Helsinki in July 2018, when even close advisors remained in the dark about the content of the talks.54 The frequent changes in the Trump administration’s top personnel contribute to the uncertainty about the US’s direction.

Congress’s most recent resolutions and draft laws have so far had a mainly symbolic significance. To actually tie the president’s hands, the bills would either have to be signed by the president himself or be put into effect with qualified majorities against the president’s veto – two highly unlikely scenarios.

In the USA, the issue is also being discussed as to whether the president could withdraw from international treaties and organisations such as NATO even against the express will of Congress.55 Another ques­tion is whether Congress could prevent the president from recalling US troops from an allied state such as Germany or South Korea.56 Neither issue has been clarified from a legal point of view. However, they are ultimately of secondary importance for the credibility of America’s security pledges. Alliance commitments demanded by Congress which the president expressly does not want to keep would be of little value in the eyes of allies.

At a minimum, however, the statements of support emanating from Congress signal to the President that he may have to pay a price if he fails to meet the security commitments made to America’s allies. In extreme cases, such failure could even cost him his re-election in November 2020. Such threats, however, would only be credible if the Republican Party were willing and able to enforce the expressions of solidari­ty with NATO made by its Congressmen and women, especially in the event of a conflict with the president.

There is no doubt that Trump has challenged some of the traditional core positions of the Republican Party in trade, foreign and security policy. At the same time, however, domestically he has successfully pushed through a conservative agenda, in particular through his tax reform and his personnel decisions for the Supreme Court as well as federal courts.57 Ultimately, domestic rather than foreign policy issues will decide Donald Trump’s political future.

The Security Environment in Europe

The second important criterion for assessing the credibility of US security commitments and US reassurance within NATO is, after domestic political conditions, the development of the European and international environment. Here, shifts in the mili­tary balance of power play a key role. An historical example is NATO’s credibility crisis in the 1960s, which was brought about by a stalemate between Washington and Moscow on strategic nuclear weap­ons,58 and by the perception of European NATO states that the Soviet Union was conventionally superior.59

Even after the end of the Cold War, the military balance of power has by no means become irrelevant. It has an impact on the costs and risks associated with security commitments, on the effectiveness of deter­rence, and on the likelihood of successful defence in a crisis or war.

Troop Presence and Military Balance of Power

After 1991, the importance of the US military pres­ence in Europe for the credibility of its security com­mitments declined. The ability to send military forces to crisis areas or to strengthen them there if necessary became the focus of attention.60 While more than 400,000 US soldiers were permanently stationed in 100 municipalities in Europe during the Cold War, by 2016 this presence had been reduced by 85 percent (measured by the number of soldiers) and 75 percent (measured by the number of bases).61

With the collapse of the Soviet Union, the issue of the credibility of US reassurance was pushed far into the background of European security policy. There were two main reasons for this: the military superiority of the USA appeared so great in all conceivable scenarios that the issue simply no longer arose; and NATO’s collective defence fell off the agenda, de facto if not on paper (i.e. in the 1991 Strategic Concept).

This was evident in the debates and decisions that led to the eastward expansion of the Alliance. They were dominated by political considerations and not by the question of how the accession countries could be defended militarily in the event of a conflict. This is particularly true of the 2004 enlargement round, in which the three Baltic republics as well as Slovenia, Slovakia, Romania and Bulgaria joined the Alliance. As of 1993 the states which would later accede to the alliance, the “old” NATO states and Russia had already considerably reduced their conventional military potential.62

Politically, the NATO-Russia Founding Act of 1997 committed NATO to refrain from the “additional per­manent stationing of substantial combat forces” in the accession states.63 The term “substantial combat forces” was not defined in the Founding Act, but an upper limit of a brigade (between 3,000 and 5,000 soldiers) has at times been mentioned as a benchmark.64 Thus, in purely military terms, during the first decade and a half following the end of the Cold War, the Alliance considerably expanded its territory, especially its north-eastern and south-eastern “flanks”, and at the same time thinned out its con­ventional capabilities.65

In direct comparison, NATO member states appear to have a much greater defence potential than Russia. Together, the allies generate a gross domestic product (GDP) of US$38 trillion (19 trillion of which is the United States),66 spend US$925 billion on defence (643 billion of which is the United States),67 and main­tain 3.2 million soldiers (1.4 million of which is the United States) in armed forces, excluding reservists.68

By contrast, Russia’s GDP is only US$1.5 trillion. The country’s defence spending is about US$45 bil­lion, and the numerical strength of the armed forces is 900,000. However, comparisons in US$ must be viewed with a degree of caution as they do not take into account purchasing power parity: Russia essen­tially covers its armaments needs from national sources and pays for them in roubles.69

More importantly, Russia would be superior to NATO in a regionally confined conflict in Eastern Europe or the Baltic, due to its military capabilities in the Baltic Sea, the enclave of Kaliningrad, Crimea and its western military district.70 Russia has invested heavily in the modernisation of its military in the past decade.71 Between 2011 and 2015, Russian mili­tary spending (measured nominally in roubles) doubled, while as a share of GDP it rose from 3.37 percent to 4.83 percent over the same period. In the following two years, however, Moscow’s military expenditure fell again.72

A study by the Swedish Defence Research Agency (FOI) concluded as early as 2016 that the Russian armed forces had developed the capability to conduct major military operations outside the territory of the former Soviet Union.73 Since 2016, Moscow has also begun to strengthen its military presence along its western border, including the establishment of a permanent military infrastructure on the border with Ukraine.74

Of particular importance to NATO are improvements in Russia’s military capabilities that would make it more difficult for the Alliance to provide military assistance to exposed eastern member states in the event of a crisis.75 This especially applies to air defence, defence against ships, submarine warfare, and the ability to attack ground targets with ballistic missiles and cruise missiles.

In the recent past, Moscow has produced additional S‑400 air defence systems76 and introduced them into the armed forces.77 The system was already stationed in Kaliningrad in February 2012.78 Russia also trans­ferred Iskander missiles to Kaliningrad in October 2016.79 This rocket is highly mobile, difficult to de­stroy in-flight, very accurate and can be equipped with conventional as well as nuclear warheads.80

How can the Alliance guarantee the indivisible security of its members?

The Russian Navy’s increasing inventory of Kalibr cruise missiles has enabled the fleet to hit targets on land up to 2,000 km from the coast.81 NATO also accuses Russia of having developed a ground-based cruise missile based on the Kalibr, with a range of 2,000 km and of already having stationed it at various locations in Russia. This cruise missile violated the Intermediate-Range Nuclear Forces (INF) Treaty. Both sea- and land-based weapons can be equipped with con­ventional and nuclear warheads.82

Since 2014 the perception of a regional military imbalance in North-Eastern Europe to the detriment of NATO has intensified the debate in the Alliance on strengthening reassurance and deterrence. In this debate, publications by leading U.S. think tanks, whose authors advocate the expansion of U.S. and NATO military presence in eastern allied countries, also play an important role.83 Two studies by the RAND Corporation on the impact of these imbalances on the Alliance’s collective defence capabilities have made waves in Washington and other NATO capitals.

In the first study of 2016, the authors concluded on the basis of “war games” (i.e. simulations) that Rus­sian armed forces would need no more than 60 hours to reach Tallinn or Riga.84 They propose that the NATO states provide seven combat brigades, at least three of them equipped with tanks, for the defence of the Baltic states.85 According to the authors, these forces would be sufficient to deny Russia the possibility of creating military facts that are difficult to alter. The second, more recent, study (2018) also concludes that the Atlantic Alliance would be “badly outnumbered and outgunned” in the first days of an armed con­flict.86

The authors also stress that the Alliance’s ability to command sufficient reinforcements at a later date is questionable. Even the most militarily powerful European NATO states – France, Great Britain and Germany – could only mobilise one armoured combat brigade at a time, and within one or two months.87 Finally, the RAND authors take a sceptical view of the United States’ ability to send sufficient troops and material across the Atlantic.88

Given the military balance of power on NATO’s north-eastern and eastern borders as described above – and despite NATO’s global conventional superior­ity – the familiar issue now arises with renewed urgency: how can the Alliance credibly provide for the indivisibility of member-state security, which it postulates politically?

Nuclear Weapons

Since 1991, both the United States and NATO have considered the threat from other nuclear powers to be relatively low. They have concentrated instead on the risks of proliferation of weapons of mass destruction and nuclear terrorism. The USA and the Soviet Union/ Russia have both significantly reduced their numbers of non-strategic nuclear weapons, in the case of the USA to an estimated 500 by the beginning of the 2000s.89 In its 2010 nuclear strategy, the Obama ad­ministration also still assumed that America’s nuclear weapons would play a less important role in defence policy, since the security environment had improved due to the fact that the USA was conventionally supe­rior to potential opponents and had made progress in missile defence.90

This optimistic picture has now worsened dramatically, and not only in the USA. Technological changes have fuelled the fears of nuclear-weapon states that they could lose their second strike capability 91 as increasingly precise missiles and cruise missiles threaten their nuclear arsenals. This also blurs the boundaries between nuclear and conventional risks. Nuclear weapons are once again viewed as a symbol of strength. Nuclear arms control is in danger of collapsing, as the end of the INF Treaty testifies.92

Russia, like the United States, is undertaking a comprehensive modernisation programme of its nuclear arsenal. With regard to strategic weapons, which have an intercontinental range due to their delivery systems, both states continue to maintain a numerical equilibrium laid down in the 2010 New Strategic Arms Reduction Treaty (New START Treaty) of 1,550 warheads each. However, this treaty expires in 2021, and it is questionable whether Moscow and Washington will be able to agree on its extension.

Much more ambiguous is the situation with so-called non-strategic or tactical weapons, which are not mounted on intercontinental missiles, long-range bombers or nuclear submarines, and thus do not fall under the existing arms control agreements for strategic weapons.

The US and NATO feel threatened by what they see as a significant imbalance in non-strategic weapons, since Russia maintains a considerably larger arsenal of these than the Alliance.93 Russia has about 1,800 such weapons, which are assigned to the various branches of the armed forces.94 It considers them compensation for the conventional superiority of the US and its NATO allies and a counterweight to China’s increasingly capable conventional armed forces.95 Especially from the perspective of NATO states in Cen­tral and Eastern Europe, the modernisation of Russia’s nuclear-capable short-range missiles through the introduction of the SS‑26 (Iskander‑M)96 is highly problematic.

According to Washington and NATO,97 Russia is pursuing an increasingly aggressive defence policy that has significantly raised the profile of nuclear weapons. The modernisation and expansion of its arsenal,98 its increase in military exercises with nucle­ar weapons-capable systems,99 and its threats of pos­sibly using nuclear weapons100 have sparked a debate about its intentions and nuclear strategy.101

The latter is often discussed under the term “escalate to de-escalate”. According to American nuclear planners, Russia is threatening a limited nuclear esca­lation – the use of short and medium-range nuclear weapons of lower yield – to put an end to any re­gional conflict on its own terms. They believe this threat to be based on the assumption that neither the USA nor NATO would risk a further escalation with Russia to the point of a comprehensive nuclear war and would capitulate instead.102 The Trump administration uses this viewpoint also as justification to Congress for the development of nuclear weapons with lower yield.

However, even Western experts on nuclear issues and on Russia take a somewhat critical view of these perceptions and assumptions about Russia’s nuclear weapons policy. They point out that there is no offi­cial Russian “escalate/de-escalate” doctrine and that the current Russian military doctrine of 2014 only provides for the use of nuclear weapons if Russia it­self is attacked with weapons of mass destruction, or if the survival of the state is at stake.103

Another criticism made of the prevailing American view is that Russian exercises with nuclear-capable weapons systems are equated with nuclear exercises. Moreover, Kristin ven Bruusgaard believes that Russia does not propagate a lower operational threshold for the use of nuclear weapons simply because the devel­opment of state-of-the-art conventional capabilities in recent years has given it sufficient alternatives for dealing with regional conflicts.104 Nevertheless, Russia deliberately spreads ambivalent messages about the role of its nuclear weapons, and the statements of individual representatives of the Russian state seem to go beyond official Russian military doctrine.105

The deterioration of the security environment and the renaissance of nuclear weapons have given new weight to US assurances within NATO. At the same time, the regional imbalances in conventional and nuclear weapons have raised the question of whether, in this changed security environment, the current military underpinning of these commitments is still sufficient.

US Military Contributions

After the domestic support and the regional security environment, specific financial, military and opera­tional contributions to European security are the third factor underpinning the credibility of its NATO commitments. The larger these contributions are, and the more specifically tailored to the changed security environment, the more credible security reassurances are.

Reassurance after Russia’s Annexation of Crimea

The number of American troops in Europe has fluctu­ated in recent years, but overall has slightly increased: in 2013 (i.e. before the annexation of Crimea) there were still around 70,200 US-soldiers, falling to 67,300 in 2016 and then rising again to just over 73,000 in 2018.106 What is clear is that the long-term trend of withdrawing American troops from Europe, which began in the mid-1980s, has come to an end.

This is largely due to the fact that since 2014 the USA has been building up and expanding its military presence in the eastern NATO states in response to Russia’s annexation of Crimea. In 2018 there were approximately 2,800 US soldiers in Poland; 1,150 in Romania; and Bulgaria, Hungary and Latvia had smaller contingents. In 2013 the USA had not yet stationed troops in any of these countries.107 More­over, Washington announced in September 2018 that it would send a further 1,500 soldiers to Germany by 2020, in addition to the approximately 38,000 already stationed there.108

Since the annexation of Crimea in 2014, the USA has expanded its military presence in the eastern NATO region, focusing on Poland.

In June 2014, the Obama administration created a specific financial instrument – the European Reassur­ance Initiative (ERI) – to expand US military contributions to reassurance in Europe and to increase the operational readiness of US troops there. Since then, the financial resources of the instrument have been significantly expanded with bi-partisan support in Congress: from an initial US$985 million in 2015 to US$6.5 billion in 2019.109 The most recent draft bud­get, presented by President Trump for the 2020 finan­cial year, provides for a slight reduction in resources for the first time, to US$5.9 billion,110 which it justi­fied by the completion of infrastructure projects.

The ERI, which has since been renamed the Euro­pean Deterrence Initiative (EDI), is not intended to in­crease the number of US troops already permanently stationed in Europe. It concerns soldiers who are ad­ditionally transferred from the USA to Europe for a limited time. Accordingly, the “core” of the presence strengthened in the course of reassurance is a brigade equipped with tanks (approximately 3,000-3,500 sol­diers, 80-90 battle tanks and other equipment), which “rotates” from the USA to Europe for nine months before being ordered back to the USA to be replaced by a new brigade.111 The brigade’s headquarters, other troops and material are located in Poland; other com­ponents are in Romania, Hungary and Bulgaria.112 From there, soldiers of the brigade will be deployed to the Baltic States for short periods for joint exercises.

The USA has increased the number of combat aviation aircraft in Germany by one brigade since the beginning of 2017, also on the rotation principle. It is equipped with military helicopters for combat, reconnaissance and transport.113 In both cases – the armoured brigade and the aviation brigade – the goal is to establish a virtually continuous American presence through the complete rotation of troops, even though soldiers and their families are not de­tached to Europe for long periods of time. Donald Trump’s EDI budget proposal for 2020 provides for a total of up to 9,400 US soldiers to be sent to Europe under the rotation model to complement the units already permanently stationed there.114

The EDI funds will also be used to finance the storage of part of the necessary army equipment and weaponry in Europe so that it does not have to be brought in from the USA in the event of a crisis. The US objective is to have sufficient equipment and am­munition in stock for an armoured army division by 2021. This material is stored at locations in Germany, Belgium, Italy, Poland and the Netherlands.115

Funds are also made available for joint exercises, expanding military infrastructure, and expanding the capacities of allied armed forces.116 Military support for Ukraine, which is controversial among NATO states, is also financed from the EDI budget to the sum of US$250 million per annum.117

US military contributions to reassurance in Europe are both based on bilateral agreements with the coun­tries concerned and closely integrated into NATO’s multinational context. They aim to support the plans and measures adopted and implemented by the Alliance at its summits in Wales (2014), Warsaw (2016) and Brussels (2018).118

For example, the USA leads one of the four multinational combat groups of the Enhanced Forward Presence (EFP), which are stationed in the Baltic re­publics and in Poland. The United States is the EFP lead nation in Poland and participates with 889 sol­diers; the other contributing states to the NATO battle group are the United Kingdom, Romania and Croatia.119 The USA also supports the Alliance’s Very High Readiness Joint Task Force (VJTF) in exercises.120

The fact that Washington expects additional Euro­pean efforts in return for these contributions is demonstrated by the NATO Readiness Initiative, which the Alliance adopted in June 2018 on the initiative of the United States. According to the plan, NATO states will together be able to make 30 army battalions, 30 flying squadrons and 30 combat ships ready for action within 30 days. This goal is to be achieved by 2020 to improve the operational readiness of existing national armed forces.121

US financial and military contributions since 2015 are not only relevant to the size of its presence in Europe. They have a specific qualitative dimension too. The Anti-Access/Area-Denial threat (A2/AD), meaning Russia’s ability to make NATO’s access to the more exposed eastern allies difficult or even impossible in the event of a conflict, points to the importance of the specific capabilities of the air force and navy.122

The European NATO states remain highly dependent on the US in key military areas, such as air defence.

The USA has started to use ERI/EDI funds to develop the air force infrastructure in the Baltic States and Poland for joint use with the host country. This in­cludes investments in airfields and materiel depots.123 The temporary dispatch of US fifth-generation fighter aircraft to Europe was also highly symbolic and visible. This generation of jets, which includes the F22‑ and F‑35, is of great significance because, in the event of a conflict, its special camouflage and electronic charac­teristics would be relied on to penetrate Russia’s increasingly capable air defence system. The USA is planning the first permanent stationing of F‑35 in Europe for 2021. The location will be the British Air Force base Lakenheath.124

In this military sector of modern combat aircraft, European NATO states for the time being remain highly dependent on the USA and its technology, especially while their own European projects – the British Tempest and the Franco-German Future Combat Air System – are still in their infancy. From 2015 to 2017, the US Air Force sent F‑22 jets annually to Germany and Great Britain for manoeuvres; they were also used in exercises in Estonia, Poland, Lithuania and Romania.125

Another important area of US reassurance in Europe concerns the maritime component, specifically warfare against submarines. The US military is wor­ried about the modernisation of Russian submarines and increased Russian submarine activities, which has not existed at this level since the 1980s, according to the Chief of the US European Command.126 The US President most recently requested US$343 million to combat submarine threats (Theatre Anti-Submarine Warfare) as part of the EDI.127

US Security Commitments and Hybrid Threats

Since the deterioration of relations with Russia, NATO has been increasingly concerned with hybrid threats. These threats are essentially scenarios which are char­acterized by “the use of military and nonmilitary tools in an integrated campaign”.128 Although this form of warfare is by no means new, its technological potential has multiplied in recent years. Hybrid war­fare is not only directed against the opponent’s regu­lar armed forces, but is also aimed at influencing domestic policy and domestic power struggles in the target state.129

Hybrid threats pose two key problems for the credi­bility of security reassurances. First, the question arises as to whether states and alliances such as NATO have effective means and capabilities to counter the non-military components of the threat. The activities carried out by the USA in the ERI/EDI and EFP frame­works are hardly suited to combating cyber attacks, and dealing with disinformation campaigns as well as other means of political subversion.130

Beyond military instruments, the security policy and administrative structures in the USA have so far been insufficiently geared to dealing with hybrid threats. The former commander of the US European Command, General Scaparrotti, had already pointed out the existing deficits during a Congressional hear­ing in 2017. It is true that new structures have been created in Washington to better withstand hybrid threats from Russia. These include the Russia Informa­tion Group and the Global Engagement Center, which work under the auspices of the State Department. According to Scaparrotti, however, these struc­tures lack political leadership and resources.131

Second, the hybrid nature of a threat renders poli­tical consensus difficult to achieve, especially in a multinational alliance context. Hybrid attacks on a NATO state cannot be identified as clearly or as early as conventional military strikes. The scenario of a hybrid attack leaves much more room for different political interpretations as to whether or not the threshold of escalation has been exceeded to the ex­tent that it triggers the defence clause under Article 5 of the NATO Treaty.

The power struggle in Washington over Trump’s contacts with Russia has damaged the credibility of American security policy.

In terms of US security policy, President Trump was very vulnerable for some time to the accusation of collusion with Moscow in connection with the 2016 US presidential and congressional elections. It was not until the investigations were concluded in March 2019 that, from Trump’s perspective, the situa­tion eased, since special investigator Robert Mueller found no evidence to support the accusation of col­lusion with Russia.

Trump did not shy away from attacking and systematically discrediting the US intelligence agencies in his defence against this domestic political danger. Yet confidence in the information of one’s own intel­ligence services is an essential foundation for count­ering the dangers of disinformation and subversion in the context of hybrid warfare.132 The domestic power struggle in Washington over Russia’s interference in the US elections has therefore also damaged the credibility of American policy in dealing with such threats.

Extended Nuclear Deterrence

US nuclear weapon doctrines under Obama and Trump fundamentally differ in their underlying per­spective on the international security environment. While the former still assumed a relatively favourable environment for the USA, the latter sees conflicts and competitors virtually everywhere who want to chal­lenge the USA, politically and militarily.

The Trump administration thus estimates the sig­nificance of nuclear weapons in US defence policy to be substantially higher than the Obama administration. At the same time, nuclear arms control plays a much smaller role for the Trump administration than the predecessor. It justifies this by asserting that other nuclear powers – first and foremost Russia and China – are modernising and expanding their arse­nals, whereas the USA has reduced its weapons stock by more than 85 percent since the height of the Cold War.133

In terms of the importance of extended deterrence and nuclear reassurance for allies, however, there is more continuity between the two administrations. From NATO’s point of view, “The strategic forces of the Alliance, particularly those of the United States, are the supreme guarantee of the security of Allies.”134 Consequently, these weapons serve to protect not only America, but also its allies. The Trump administration’s Nuclear Posture Review (NPR) reinforces this political commitment.

The Obama administration had already initiated an extensive programme to modernise the so-called nuclear “triad,” which has been continued under the Trump presidency. It includes the development of new submarines (Columbia class), new intercontinental missiles and a new long-range bomber (B‑21 Raider).135

Previous debates on the nuclear weapons policy of the USA in NATO mostly revolved around the 150 to 200 non-strategic type B‑61 drop bombs still stationed in Europe. These are stored in five countries (Germany, Italy, the Netherlands, Belgium and Turkey) and would, in the event of war, also be conveyed to their targets by aircraft from the stationing countries as part of nuclear sharing. Other NATO countries, such as the Czech Republic, Hungary, Poland and Romania, are making non-nuclear contributions to exer­cises designed to prepare for such a scenario.136

Here, too, the USA pursues the same course under Trump as previous administrations, maintaining the presence of B‑61 bombs in Europe, but also continuing the programme of modernizing these weapons. A new version of this bomb – more accurate and with variable explosive yield – should be available by 2021.137

Unlike Obama’s nuclear strategy, however, Trump’s focuses on making the US nuclear capability more flexible. According to the justification in the 2018 NPR, the US President needs a spectrum of “limited and graduated options, including a variety of delivery systems and explosive yields”138 to deter a n­uclear or “non-nuclear strategic” attack. This re­quirement is also directly related to US security com­mitments to its allies. Washington could credibly deter a nuclear attack on the territory of the USA with its existing strategic arsenal. According to the NPR, making the nuclear options more flexible would therefore primarily serve as a deterrent in regional crises in Europe or Asia.

Specifically, this is to be achieved through three supplements to the strategic “triad”. First, the capability for deploying nuclear-capable aircraft is to be main­tained and, if necessary, expanded, inter alia through the introduction of the F‑35 fighter jet and corresponding contributions from NATO partners. Second, an unspecified number of sea-based ballistic missiles will be modified with low yield warheads and, third, a new sea-based cruise missile will be developed (whose predecessor Obama had abolished).139

The assumption in the 2018 NPR is that these new options would make a catastrophic conflict less likely because they would increase deterrence.140 At the same time, US nuclear planners see flexible options as a way of limiting damage for the US and its allies in the event that de­terrence fails nonetheless.141 Critics, on the other hand, warn against planning for nuclear warfare based on what they consider to be the mis­taken as­sumption that the use of nuclear weapons is “possible and controllable below the threshold of strategic destruction risk”.142

The possible solutions endorsed by the Trump ad­ministration in its 2018 NPR to make nuclear options more flexible were specifically designed not to violate the INF Treaty. This agreement between Russia and the USA prohibited the testing, possession and sta­tioning of land-based shorter and medium-range mis­siles and cruise missiles with a range between 500 and 5,500 km. In October 2018, President Trump responded to the Russian violation of this bilateral treaty by announcing the US’s withdrawal from it. This an­nouncement was finally executed on August 2, 2019, thus ending the INF Treaty. There has been speculation among European NATO states as to whether Washington also intends to station medium-range missiles in Europe in the future. When President Trump announced his intention to leave the INF Treaty, he threatened to develop these weapons.143

For the time being, Washington has no intention of stationing any new nuclear weapons in Europe after the end of the INF Treaty.

In fact, the US Department of Defense has been working on such options since at least 2013, and Con­gress has provided the necessary funds in the past.144 The 2018 NPR also officially confirms that the USA has already begun initial research and development work on new land-based medium-range missile systems.145 The development of these weapons (as opposed to their testing) was not prohibited by the INF Treaty.

In early 2019, the American NATO ambassador Kay Bailey Hutchison let it be known that the USA does not intend to bring land-based nuclear missiles to Europe.146 Under the 2018 NPR, the Trump administration instead relies on sea-launched missiles or cruise missiles for regional deterrence.

Overall, during Trump’s presidency the US has increased its financial, military and operational con­tributions to underpinning conventional and nuclear security commitments to European NATO countries. The contributions have specifically taken into account the military imbalances and vulnerabilities that have unsettled some allies, particularly those in Eastern Europe, since 2014. The USA has expanded its military presence in the eastern alliance area and increased its air defence and anti-submarine capabilities. Among NATO states, however, very different assessments per­sist of what would actually be conducive to European security: whether, for example, it would be suitable to permanently deploy more US or NATO troops to the eastern member states and/or expand the nuclear options, as discussed above.

The Perspectives of Eastern NATO Allies

The three factors examined in this study, which form the basis for the credibility of conventional and nucle­ar reassurance by the USA, are assessed and weighted differently among allies. Respective risk and threat perceptions are a major reason for these di­verging views.147 This is illustrated below by a number of east­ern allies who feel particularly exposed to Russia’s threats.

Conventional Reassurance

The distinction between US troops permanently stationed in Europe and those that “rotate permanently” may be of secondary importance in terms of deterrence – where the addressee is Russia – but from the point of view of reassurance it is politically relevant for some eastern NATO countries.

For many years (i.e. not only since either Donald Trump or the right-wing government in Warsaw took office), Poland has been pushing for US troops to be permanently stationed on its territory. In spring 2018, the Polish Ministry of Defence presented a proposal to station a whole US division in Poland. In return, War­saw offered Washington substantial funds to finance this presence: US$1.5 to US$2 billion have been men­tioned in this context.148

The proposal has met with reservations in NATO, because it can be read as a special bilateral agreement between the USA and Poland and, moreover, contra­dicts the NATO-Russia Founding Act of 1997, which Berlin (among others) insists must be observed. Po­land’s intentions therefore risk splitting the Alliance.

Demands for US troops to be more present in some eastern NATO countries may also reflect distrust of Trump.

Other states in the eastern part of NATO have also shown interest in a larger and more permanent US military presence on their respective territories.149 Diplomats from the Baltic countries sometimes express disappointment that, in the wake of the reassurance measures decided by NATO since 2014, the US military presence would focus primarily on Poland. In contrast, the deployment of troops in the Baltic States is limited to relatively short periods of multinational exercises with American participation.150 In April 2019, Lithuania became the first of the Baltic countries to sign a bilateral defence cooper­ation agreement with the USA.151 Latvia and Estonia then followed suit with similar agreements.

However, these countries are not only interested in greater reassurance vis-à-vis Russia, but also vis-à-vis the uncertainties in American domestic policy. The former commander of the US army in Europe, General Ben Hodges, said that one of the reasons why the east­ern Alliance partners had an interest in a permanent US military presence was “because they believe it would be a little bit more difficult for the U.S. to turn it off”.152

Demands for a more extensive and permanent presence of US military may therefore also reflect to some degree a lack of confidence in President Trump. The mistrust of the exposed Allies also extends to other partners and NATO as a whole. Poland and the Baltic countries look with great scepticism at Ger­many’s Russia policy.153 Germany’s adherence to the Nord Stream 2 gas pipeline has increased these concerns.

In the event of a political blockade in the NATO Council – a scenario whose probability grows with hybrid threats – the US would be the only ally that is capable of unilateral military action. Following this logic, the US is indispensable as a kind of “silent con­ventional deterrence”.154 As Estonian President Kersti Kaljulaid put it in April 2018, “Some people might think that NATO takes a long time to act, but the US could be quicker. There is some rationale in this thinking.“155

What is also decisive is that the US president’s criticisms of the NATO alliance are countered by the US’s ongoing operational-military cooperation with NATO states, a cooperation that in the eyes of some rep­resentatives of the eastern NATO states is now deeper and more far-reaching than under Obama’s presidency.

From the point of view of the Baltic States, air defence and missile defence are especially delicate subjects. These countries feel extremely vulnerable given that their own resources in this sector are rudimentary or non-existent.156 Geography plays an equally important role here. The three countries border both Russia and the increasingly militarised Russian enclave of Kaliningrad. Moreover, they are only connected to the rest of NATO territory via a very narrow land corridor.

In February 2018, for example, the USA responded to such concerns by sending the Patriot missile de­fence system to Estonia, where it is being used for training purposes. Latvia, too, has repeatedly put the need to develop better air defence in the Baltic region on the agenda.157 The Baltic countries are also pres­sing for NATO air policing158 to be further developed into air defence. This would mean more robust rules of engage­ment and deeper integration with ground-based air defence systems.159

These factors explain why, at least for some eastern NATO states, a continued or enhanced US presence remains of great security importance despite – or even because of – the imponderables of the Trump administration.160 It is noteworthy in this context that Finland and Sweden also expanded their defence co­operation with the USA in May 2018.161 As non-NATO states, they do not enjoy the benefit of the collective assistance pledge, but they hope to improve their security situation vis-à-vis Russia by greater cooperation with the USA.

The bi- and trilateral cooperation of Finland and Sweden with the USA will cover a total of seven issues, including regular meetings at various levels and the intensification of practical cooperation be­tween the armed forces.162 According to a report, American M1A1 Abrams tanks first participated in exercises in Finland at the same time as the trilateral Memorandum of Understanding was signed.163

Nuclear Reassurance

Russia’s nuclear weapons policy has created a great deal of uncertainty in the eastern allies.164 Nevertheless, different national views on the subject of nuclear deterrence and reassurance persist there, as a study by the European Council on Foreign Relations (ECFR) published in December 2018 shows. Poland and Romania (as well as France and the United Kingdom) are among the “true believers” in nuclear deterrence. The three Baltic republics, Bulgaria and the Czech Republic, on the other hand, belong to the “pragmatists” when it comes to nuclear deterrence within NATO. Other countries such as Slovenia or Slovakia are “conformists” according to the ECFR, who con­sider nuclear weapons to be less relevant than the other two groups.165

The credibility of US nuclear commitments pledges under Trump is also assessed differently within the EU and the European NATO states. In Germany, for example, the prevailing opinion is that these com­mitments have lost credibility during Trump’s term of office, while from Estonia’s and Poland’s point of view they have increased as the ECFR analysis indi­cates. According to the authors, one possible expla­nation for the latter two countries’ confidence is that Trump’s unpredictability may even increase the effect of nuclear deterrence.166

Another study from 2018, which examined expectations of nuclear deterrence in Estonia and Latvia, came to a similar conclusion: representatives of the security elites in these two countries considered Trump even as a presidential candidate to be more credible than his rival, Hillary Clinton, or President Barack Obama.167

The significance of nuclear weapons for reassurance is primarily political; specific crisis and deployment scenarios are of little relevance.

There is much to suggest that, despite the differences in the eastern alliance states’ perspectives, as described above, a “strategic” view of nuclear weap­ons prevails. According to this view these weapons are an important, sometimes even indispensable, part of European security and deterrence.168 They com­pensate for the regional imbalance in conventional armed forces in terms of deterrence,169 but they have little or no military value in the event that deterrence fails. Seen from this perspective, the non-strategic weapons of the USA also play a primarily political role in Europe as transatlantic anchors, and as an expres­sion of American solidarity to the Alliance.170

Accordingly, the eastern allies were long regarded as advocates of the status quo within NATO when it came to nuclear weapons policy.171 They were against a unilateral withdrawal of tactical nuclear weapons from Europe without corresponding quid pro quo from Russia.172 Deteriorating relations with Russia since 2014 and the uncertainties of the Trump administration do not seem to have fundamentally changed their preference for the status quo ante. States that joined the Alliance in 1999 and 2004 as part of its eastward enlargement are currently not advocating that nuclear weapons be stationed on their territory.

Thus far, this has also applied to Poland, although official government representatives have at times aired different ideas. In December 2015, for example, the Polish Deputy Minister of Defence, Tomasz Szat­kowski, was quoted as saying that his country was actively working to become a member of NATO’s nuclear sharing arrangements. However, the Polish Ministry of Defence immediately denied such con­siderations.173

Following the announcement that Washington would withdraw from the INF Treaty, the Polish Foreign Minister Jacek Czaputowicz advocated the deployment of American nuclear weapons in Europe at the beginning of 2019.174 However, the Foreign Ministry immediately clarified that Poland did not re­quest such weapons for itself, but only that the USA retain a nuclear presence in Europe.175

Poland attaches particular importance to nuclear threats compared to conventional or hybrid ones.176 For the Baltic countries, the focus is more on non-nuclear means of reassurance,177 as they are particularly afraid of fait accompli and hybrid scenarios. A high-ranking foreign policy official from Latvia commented that if the nuclear component came into play – for example to deter a nuclear escalation by Russia – it would be too late for his country any­way. By then Latvia would already be occupied militarily.178

For both conventional and nuclear reassurance, the credibility of the US must be assessed in relation to European alternatives.179 From the perspective of many eastern allies, Europe’s strategic autonomy remains less credible than the US offer.

This assessment was summed up, for example, by Jarosław Kaczyński, chairman of the governing Law and Justice Party (PiS) in Poland, and an influential politician in his country. Although he spoke in favour of Europe as a nuclear power in principle, he re­garded it as unrealistic. That is why according to him Poland and Europe should continue to cultivate close rela­tions with the USA, even under Trump.180

Conclusions

This study’s line of inquiry was how credible US security commitments within NATO are, and what political and security policy implications for Europe result from the findings. Two out of three factors at the heart of the analysis suggest that the credibility of US reassurance in Europe has declined markedly. Since Donald Trump’s inauguration as President of the United States, considerable doubts have been raised as to whether the United States would actually summon up the political will to defend its NATO partners with conventional, let alone nuclear, means. The unanimous support that the US Alliance com­mitments continue to enjoy in Congress, large parts of the administration and the military can at best par­tially compensate for this deficit. In the event of a crisis or war, the president is the person who really matters.

The changes in the security environment also cast doubt on the credibility of American reassurance. The expansion of Alliance territory in the wake of NATO’s eastward enlargement since 1999, the accentuation of regional military imbalances in eastern and north-eastern Europe, and the modernisation of the Russian military have – from Washington’s perspective – raised the potential costs and risks associated with the US’s security commitments. During the “unipolar moment” in the 1990s, when the US military supe­riority was still unchallenged and the circle of allies was much smaller, these commitments seemed relatively “cheap” from Washington’s point of view. This is no longer the case.

At the same time, these developments have led to a strong increase in the need for security – in other words, the demand for reassurance – in some east­ern NATO countries. The allies particularly exposed to Russia, such as Poland, the Baltic republics or Romania, but also the non-NATO states Finland and Sweden, have intensified their bilateral defence coop­eration with the United States since 2014.

The uncertainties related to Donald Trump’s presidency have not lessened, but rather increased, efforts to expand and consolidate the US military presence in Europe. To the extent that the domestic political foundations of American credibility appear uncertain, the significance of the specific financial, military and operational contributions of the USA for the reassurance of its allies deepens.

During both the Obama presidency and the first two-and-half years of Trump’s presidency, the US has made contributions in areas where European defence is still seriously flawed and where some Eastern Euro­pean NATO countries feel very vulnerable. This in­cludes, inter alia, reconnaissance and air defence, as well as the deployment of army units equipped with heavy tanks.

Some states, such as France or Germany, consider the security threat posed by Russia to be comparatively low for various reasons. It seems plausible to assume that these countries can afford a rather “abstract” understanding of the credibility of American reas­surance. This understanding is based mainly on the statements of the US President and less on specific military contributions of the United States.

Trump’s ambivalent statements about NATO and his “America First” programme have raised the legiti­mate question as to whether this particular President would really be willing to use nuclear weapons to defend the allies in extremis. And yet neither allies nor opponents can predict with any certainty how the US president would react in the event of a crisis. In view of the enormous destructive power of nuclear weapons, miscalculations would have catastrophic consequences. Like previous governments, the Trump administration has unambiguously committed itself to extended nuclear deterrence. Against this background, some NATO countries, especially eastern NATO countries, continue to believe that the US nu­clear umbrella remains credible – or at least more credible than the possible alternative of a purely European deterrent.

However, Trump’s nuclear planners want to further underpin the credibility of the nuclear commitments by making America’s nuclear options more flexible. This is to be achieved primarily by the development of new weapons with lower explosive yield and the reintroduction of a sea-based, nuclear-armed cruise missile. The underlying idea is that the US could limit the damage to itself if nuclear weap­ons were used in a regional war in Europe or Asia. By the same logic, this also increases the credibility of its security commitments to its allies.

By contrast, eastern Allies have a more political and strategic understanding of the importance of nuclear weapons. Thus, specific questions of nuclear capa­bility – how many nuclear bombs are stationed on which carrier systems, and what their explosive yield is – are less important for them. Similarly, where the non-strategic nuclear weapons of the USA in Europe are concerned, from an assurance perspective it is fundamentally crucial that they are there.

The credibility of US security commitments – both conventional and nuclear – is a multifaceted phenomenon that cannot be reduced to the US presi­dent’s statements alone. The European NATO states consider and weight the underlying factors differently. Greater insight among political decision-makers, not least in Germany, about this diversity is indispensable for further political cohesion in the EU and NATO.

Abbreviations

A2/AD Anti-Access/Area-Denial

ACA Arms Control Association

BASIC British American Security Information Council

CES Central Eastern States

CRS Congressional Research Service

CSBA Center for Strategic and Budgetary Assessments

CSIS Center for Strategic and International Studies

DoD Department of Defense

ECFR European Council on Foreign Relations

EDI European Deterrence Initiative

EFP Enhanced forward presence

ERI European Reassurance Initiative

EU European Union

EUCOM (U.S.) European Command

FOI Swedish Defence Research Agency

FY Fiscal Year

GDP Gross domestic product

ICDS International Centre for Defence and Security (Estonia)

IFSH Institute for Peace Research and Security Policy at the University of Hamburg

INF Intermediate Range Nuclear Forces

MDR Missile Defense Review

NAFTA North American Free Trade Agreement

NATO North Atlantic Treaty Organisation

New START New Strategic Arms Reduction Treaty

NPR Nuclear Posture Review

NSS National security strategy

PiS Law and Justice (Poland)

PISM Polish Institute of International Affairs

RAF Royal Air Force

SNOWCAT Support of Nuclear Operations With Conventional Air Tactics

USAFE U. S. Air Forces in Europe

USEUCOM U. S. European Command

VJTF Very High Readiness Joint Task Force

Endnotes

1

 Thomas C. Schelling, Arms and Influence. With a New Fore­word and Preface, The Henry L. Stimson Lectures (New Haven, 2008), 36.

2

 See Robert J. McMahon, “Credibility and World Power. Exploring the Psychological Dimension in Postwar American Diplomacy”, Diplomatic History 15, no. 4 (1991): 455–72 (457).

3

 In his historical study, Daryl Press has shown that the credibility of military threats in the eyes of those being threatened does not primarily depend on past behavioural patterns, but on the interests of the threatening state and its specific military and economic capabilities. See Daryl G. Press, Calculating Credibility. How Leaders Assess Military Threats, Cornell Studies in Security Affairs (Ithaca, 2005), 24.

4

 “Non-strategic” (also called “tactical”) nuclear weapons are those that are not covered by the New Strategic Arms Reduction Treaty (New START). “Strategic weapons” in the sense of New START are land- and sea-based ballistic missiles with a range of more than 5,500 km as well as nuclear armed “strategic” bombers.

5

 See Stéfanie von Hlatky, “American Alliances and Extend­ed Deterrence”, in The Future of Extended Deterrence. The United States, NATO, and Beyond, ed. Stéfanie von Hlatky and Andreas Wenger (Washington, D. C., 2015), 1–16 (5).

6

 On the two perspectives, see also David S. Yost, “Assurance and US Extended Deterrence in NATO”, International Affairs 85, no. 4 (2009): 755-80 (772); Peter Rudolf, US Nuclear Deterrence Policy and Its Problems, SWP Research Paper 2018/ RP 10 (Berlin: Stiftung Wissenschaft und Politik, November 2018), 27, https://www.swp-berlin.org/en/publication/us-nuclear-deterrence-policy-and-its-problems/ (accessed 20 May 2018).

7

 Schelling, Arms and Influence (see note 1), 91.

8

 ”Automatic action-response mechanisms” are mechanisms that are deliberately intended to restrict one's own political scope for action in crisis situations. This is meant to increase credibility, both of security commitments to allies and of threats to opponents. An example would be the use of nuclear weapons in certain situations under extreme time pressure and correspondingly prepared protocols: for exam­ple, when enemy missiles are launched or one’s own troops are attacked.

9

 See Schelling, Arms and Influence (see note 1), 110. Schelling clarifies this point using the analogy of a modified chess game: a single move can cause both players to lose immediately. In this version of the game, the white knight is just as “powerful” as the black queen. See ibid., 99ff.

10

 See Richard J. Harknett, “The Logic of Conventional Deterrence and the End of the Cold War”, Security Studies 4, no. 1 (1994): 86–114 (102).

11

 The ”scalability” of conventional weapons implies that policy-makers are offered a broader spectrum of action than with nuclear means. Conventional weapons can be used to cause little, moderate or massive damage to the opponent. This is not possible with nuclear weapons, or at least not possible to the same extent, due to their enormous destructive power.

12

 See Michael S. Gerson, “Conventional Deterrence in the Second Nuclear Age”, Parameters 39, no. 3 (2009): 32–48 (33).

13

 See John Stone, “Conventional Deterrence and the Challenge of Credibility”, Contemporary Security Policy 33, no. 1 (2012): 108–23 (109).

14

 Richard J. Harknett has formulated this as follows for the conventional context: “In a conventional environment, the issue of credibility is dominated by suspicion about the capability to inflict costs rather than on the decision to inflict costs. [...] [T]he most problematic area of conventional deter­rence is in establishing a credible capability.” See Harknett, “The Logic of Conventional Deterrence” (see note 10), 89 (added emphasis). Even though this assessment relates to deterrence, it can also be applied to the notion of reassurance.

15

 In the “great debate” of 1951, Herbert Hoover and the Republican Senator Robert Taft called for the reduction of US troops in Europe under the motto “Fortress America”. The initiatives by the Democratic senators Mike Mansfield in 1966 and Sam Nunn in 1984 also provided for a reduction of US military presence in Europe. See Phil Williams, The Senate and US Troops in Europe (New York, 1985), 262, 271, 273. For a historical overview of the domestic dimension of the deploy­ment of American troops in Europe, see Hubert Zimmermann, “The Improbable Permanence of a Commitment. America's Troop Presence in Europe during the Cold War”, Journal of Cold War Studies 11, no. 1 (2009): 3-27.

16

 Patrick Callahan, Logics of American Foreign Policy. Theories of America’s World Role (New York, 2004), 12.

17

 See Amos A. Jordan et al., American National Security, 5. ed. (Baltimore, 1999), 80–81.

18

 Quoted in David A. Shlapak and Michael W. Johnson, Reinforcing Deterrence on NATO’s Eastern Flank: Wargaming the De­fense of the Baltics (Santa Monica: RAND Corporation, 2016), 3, https://www.rand.org/content/dam/rand/pubs/research_reports/RR1200/RR1253/RAND_RR1253.pdf (accessed 21 May 2019).

19

 In March 2019 US media reported that President Trump intended to submit a plan entitled “Costs plus 50” to countries in which US troops are stationed. This means that Alliance partners will not only pay for the full costs of these troop deployments, but will also pay a 50 percent surcharge as a premium for the American presence. See Ellen Mitchell, “Pentagon: Trump’s ‘Cost Plus 50’ Plan Hasn’t Been Discussed with Europe”, The Hill (online), 13 March 2019, https://thehill.com/policy/defense/433883-pentagon-trumps-cost-plus-50-plan-hasnt-been-discussed-with-europe (accessed 27 May 2019).

20

 See David E. Sanger and Maggie Haberman, “Donald Trump Sets Conditions for Defending NATO Allies against Attack”, New York Times (online), 20 July 2016, https://www. nytimes.com/2016/07/21/us/politics/donald-trump-issues.html (accessed 21 May 2019).

21

 See Stephanie Condon, “Donald Trump: Japan, South Korea Might Need Nuclear Weapons”, CBS News (online), 29 March 2016, https://www.cbsnews.com/news/donald-trump-japan-south-korea-might-need-nuclear-weapons/ (accessed 21 May 2019).

22

 ”Extended nuclear deterrence” means the US threat of using nuclear weapons not only to protect American territory, but also that of its allies.

23

 See Lorenz Hemicker and Michael Stabenow, “Trump lässt die Puppen tanzen”, in: Frankfurter Allgemeine Zeitung, 13 July 2018, p. 2.

24

 Quoted in “Trump: I’m Not Pro-Russia, I Just Want Our Country Safe”, Fox News, 17 July 2018.

25

 See Julian E. Barnes and Helene Cooper, “Trump Discus­sed Pulling U. S. from NATO, Aides Say amid New Concerns over Russia”, New York Times, 14 January 2019.

26

 Quoted in Joe Gould, “US House Votes Overwhelmingly to Bar US Exit from NATO”, Defense News (online), 22 January 2019, https://www.defensenews.com/congress/2019/01/23/us-house-votes-overwhelmingly-to-bar-us-exit-from-nato/ (accessed 21 May 2019).

27

 Quoted in Jonathan Swan, “Scoop: Trump’s Private NATO Trashing Rattles Allies”, Axios (online), 28 June 2018, https://www.axios.com/donald-trump-foreign-policy-europe-nato-allies-worried-bd1e143a-e73a-415b-b688-d18ab2d902e7.html (accessed 21 May 2019).

28

 The White House, “Remarks by Vice President Pence at the 2019 Munich Security Conference”, Washington, D.C., 16 February 2019, https://www.whitehouse.gov/briefings-statements/remarks-vice-president-pence-2019-munich-security-conference-munich-germany/ (accessed 3 May 2019).

29

 See Michael Wolff, Fire and Fury. Inside the Trump White House (New York, 2018); Bob Woodward, Fear. Trump in the White House (London and New York et al., 2018).

30

 Elizabeth N. Saunders, “Sure, Trump’s Advisers Aren’t the First to Push Back against a President. But What’s Happening Now Is Completely Unprecedented”, Washington Post (online), 6 September 2018. An opinion piece by an unnamed “senior official” garnered most attention: “I Am Part of the Resistance inside the Trump Administration”, New York Times (online), 5 September 2018, https://www. nytimes.com/2018/09/05/opinion/trump-white-house-anonymous-resistance.html (accessed 21 May 2019).

31

 See Andrew Hanna, “Flynn to Recommend Trump Back NATO Membership for Montenegro”, Politico (online), 6 February 2017, https://www.politico.com/story/2017/02/ trump-nato-montenegro-michael-flynn-234697 (accessed 21 May 2019); Ellen Mitchell, “Rand Paul Roils the Senate with NATO Blockade”, The Hill (online), 22 March 2017, https://thehill.com/news-by-subject/defense-homeland-security/325091-rand-paul-roils-the-senate-with-nato-blockade (accessed 6 May 2019).

32

 See Helene Cooper and Julian E. Barnes, “Rush to Protect NATO Accord against Trump”, New York Times, 10 August 2018.

33

 Hal Brands, American Grand Strategy in the Age of Trump (Washington, D.C., 2018), 124.

34

 See United States European Command (USEUCOM), EUCOM Posture Statement 2018. Statement of General Curtis M. Scaparrotti, United States Army Commander, United States Euro­pean Command before the United States Senate Committee on Armed Services, Stuttgart, 8 March 2018, https://www.eucom. mil/media-library/article/36269/eucom-2018-posture-statement (accessed 21 May 2019).

35

 See USEUCOM, House Armed Services Committee Hearing on Security Challenges in Europe (Stuttgart, 15 March 2018), https://www.eucom.mil/media-library/transcript/36275/house-armed-services-committee-hearing-on-security-challenges-ineurope (accessed 21 May 2019).

36

 The 2015 military strategy drafted by the Obama ad­ministration’s Joint Chiefs of Staff already reflected the US military's desire to oppose “revisionist states” – it listed Russia, Iran, North Korea and China – and advocated strengthening the global network of US alliances and part­ners to this end. See Joint Chiefs of Staff, The National Military Strategy of the United States of America 2015. The United States Military's Contribution to National Security (Fort Belvoir: United States Department of Defense [DoD], 2015), 1-2, https://www. jcs.mil/Portals/36/Documents/Publications/2015_National_ Military_Strategy.pdf (accessed 21 May 2019).

37

 National Security Strategy [NSS] of the United States of America (Washington, D.C.: President of the United States of America, December 2017), 2, 48, https://www. whitehouse.gov/wp-content/uploads/2017/12/NSS-Final-12-18-2017-0905.pdf (accessed 6 May 2019).

38

 See James Mattis, Summary of the 2018 National Defense Strategy of the United States of America (Washington, D.C.: DoD, January 2018), https://dod.defense.gov/Portals/1/Documents/ pubs/2018-National-Defense-Strategy-Summary.pdf (accessed 20 May 2019).

39

 See DoD, Nuclear Posture Review [NPR] (Washington, D.C., February 2018), VIII, https://media.defense.gov/2018/Feb/ 02/2001872886/-1/-1/1/2018-NUCLEAR-POSTURE-REVIEW-FINAL-REPORT.PDF (accessed 6 May 2019).

40

 Frank Rose, who was in charge of arms control in the US State Department during the Obama presidency said: “Similar to the 2010 NPR [Nuclear Posture Review], the 2018 NPR established an effective consultation process that enabled allies to provide input and help shape the review.” Frank A. Rose, Is the 2018 Nuclear Posture Review as Bad as the Critics Claim It Is?, Policy Brief (Washington, D.C.: The Brookings Institution, April 2018), 4, https://www.brookings.edu/ research/is-the-2018-nuclear-posture-review-as-bad-as-the-critics-claim-it-is/ (accessed 6 May 2019).

41

 See Executive Summary, National Missile Review [MDR] (Washington, D.C.: DoD, January 2019), https://www.defense. gov/Portals/1/Interactive/2018/11-2019-Missile-Defense-Review/The%202019%20MDR_Executive%20Summary.pdf (accessed 20 May 2019).

42

 This cross-party consensus is evident, for instance, in the Congressional debates on US armed forces in Europe. See USEUCOM, Senate Armed Services Committee Hearing on the United States European Command, F. Y. [Fiscal Year] 2019, (Stuttgart, 12 March 2018), https://www.eucom.mil/media-library/transcript/36273/senate-armed-services-committee-hearing-on-the-united-stateseuropean-command-f-y-2019 (accessed 21 May 2019); USEUCOM, House Armed Services Committee Hearing (see note 35).

43

 See, e.g., USEUCOM, EUCOM Commander Testifies before House Armed Services Committee (Stuttgart, 28 March 2017).

44

 See John Vandiver, “Lawmakers Prod Pentagon to Con­sider More Europe-based Troops”, Stars & Stripes (online), 24 July 2018, https://www.stripes.com/news/lawmakers-prod-pentagon-to-consider-more-europe-based-troops-1.539189 (accessed 6 May 2019).

45

 See Rose, Is the 2018 Nuclear Posture Review as Bad as the Critics Claim It Is? (see note 40), 3.

46

 See Joe Gould, “Tactical Nuclear Weapon Launches into Development with Pentagon Policy Bill”, Defense News (online), 24 July 2018, https://www.defensenews.com/congress/2018/07/24/tactical-nuclear-weapon-launches-into-development-with-pentagon-policy-bill/ (accessed 6 May 2019). The 2019 defence budget approved by Congress provides US$65 million for the devel­opment of these sea-based missiles. See Brendan W. McGarry and Pat Towell, FY 2019 National Defense Authorization Act. An Overview of H. R. 5515, CRS In Focus (Washington, D. C.: Congressional Research Service [CRS], 7 August 2018), 2, https://fas.org/sgp/crs/natsec/IF10942.pdf (accessed 24 November 2018).

47

 See United States Senate, Hearing to Receive Testimony on United States European Command. Stenographic Transcript (Washington, D.C., 23 March 2017), 49ff., https://www.armed-services.senate.gov/imo/media/doc/17-24_03-23-17.pdf (accessed 20 May 2019).

48

 Quoted in Joe Gould, “Bill Would Make Pentagon Track Allied Defense Spending for Congress”, Defense News (online), 12 July 2018, https://www.defensenews.com/smr/nato-priorities/2018/07/12/bill-would-make-pentagon-track-allied-defense-spending-for-congress/ (accessed 21 May 2019).

49

 See Niels Lesniewski, “Senate Plans to Revive NATO Ob­server Group. Senate Organization First Developed in 1997 Ahead of New NATO Admissions”, Roll Call (online), 28 Feb­ruary 2018, https://www.rollcall.com/news/policy/senate-plans-revive-nato-observer-group (accessed 6 May 2019); “US Senate Revives NATO Observer Group”, NATO Watch (online), 3 March 2018, http://natowatch.org/newsbriefs/2018/us-senate-revives-nato-observer-group (accessed 6 May 2019).

50

 See Brett Samuels, “House Passes Resolution in Support of NATO by Unanimous Voice Vote”, in: The Hill (online), 11 July 2018, https://thehill.com/homenews/house/396536-house-passes-resolution-in-support-of-nato-by-unanimous-voice-vote (accessed 6 May 2019); Avery Anapol, “Senate Votes to Support NATO ahead of Trump Summit”, The Hill (online), 10 July 2018, https://thehill.com/homenews/adminis tration/396399-senate-overwhelmingly-passes-resolution-supporting-nato-as-trump (accessed 6 May 2019).

51

 See Gould, “US House Votes Overwhelmingly to Bar US Exit from NATO” (see note 26).

52

 See Jordain Carney, “Bipartisan Senators Reintroduce Legislation to Slap New Sanctions on Russia”, The Hill (online), 13 February 2019, https://thehill.com/homenews/ senate/429880-bipartisan-senators-reintroduce-legislation-to-slap-new-sanctions-on-russia (accessed 6 May 2019).

53

 See North Atlantic Treaty Organization (NATO), NATO Secretary General Addresses Historic Joint Meeting of the United States Congress (Brussels, 3 April 2019), https://www. nato.int/cps/en/natohq/news_165249.htm (accessed 23 May 2019).

54

 See Karen DeYoung et al., “As Russians Describe ‘Verbal Agreements’ at Summit, U.S. Officials Scramble for Clarity”, Washington Post (online), 19 July 2018.

55

 See Harold Hongju Koh, “Presidential Power to Terminate International Agreements”, The Yale Law Journal Forum, no. 128 (2018).

56

 See Ashley Deeks, Can Congress Constitutionally Restrict the President’s Troop Withdrawals?, 6 February 2019, https://www. lawfareblog.com/can-congress-constitutionally-restrict-presidents-troop-withdrawals (accessed 12 June 2019).

57

 See Bobby Jindal, “Why Republicans Stick With Trump”, Wall Street Journal, 30 August 2018, A15.

58

 For an explanation of this term, see note 4.

59

 See Helga Haftendorn, NATO and the Nuclear Revolution. A Crisis of Credibility, 1966–1967 (Oxford, 1996), 388.

60

 See Gary L. Guertner, “Deterrence and Conventional Military Forces”, Small Wars & Insurgencies 11, no. 2 (2000): 60–71 (66).

61

 USEUCOM, U. S. Military Presence in Europe (1945–2016) (Stuttgart, 26 May 2016), 1, https://www.eucom.mil/doc/ 35220/u-s-forces-in-europe (accessed 20 May 2019).

62

 For further details, see The Military Balance 117, no. 1 (2017): 63–182 (67) (Chapter Four. Europe).

63

 NATO, Founding Act on Mutual Relations, Cooperation and Security between NATO and the Russian Federation signed in Paris, France (Paris, 27 May 1997), https://www.nato.int/cps/en/ natohq/official_texts_25468.htm?selectedLocale=en (accessed 21 May 2019).

64

 See Thomas Gutschker, “Die NATO muss schneller werden”, Frankfurter Allgemeine Sonntagszeitung, 15 July 2018, 2; Wissenschaftlicher Dienst des Deutschen Bundestages, Zulässigkeit rotierender Truppen in den östlichen Mitgliedstaaten der NATO, WD 2-3000-077/16/2016 (Berlin, 24 May 2016), 7, https://www.bundestag.de/blob/433612/086dbea48fe4aa67d522df6817d48470/wd-2-077-16-pdf-data.pdf (accessed 21 May 2019).

65

 For a discussion on how this has had a negative impact on the credibility of US security commitments see Joshua Shifrinson, “Time to Consolidate NATO?”, in: The Washington Quarterly, 40 (2017) 1, p. 109-23 (110).

66

 The World Bank, World Development Indicators Database (Washington, D.C.), https://databank.worldbank.org/data/ reports.aspx?source=2&series=NY.GDP.MKTP.CD (accessed 24 May 2019). The figures refer to the year 2017.

67

 Defence spending in current US$ “International Comparisons of Defence Expenditure and Military Personnel”, The Military Balance 119, no. 1 (2019): 513-18. The figures refer to 2018.

68

 Ibid; The Military Balance 119, no. 1 (2019): 21-27 (Chapter Two: Comparative Defence Statistics). The figures refer to 2018.

69

 See Michael Kofman, “Russian Defense Spending Is Much Larger, and More Sustainable Than It Seems”, Defense News (online), 3 May 2019, https://www.defensenews.com/ opinion/commentary/2019/05/03/russian-defense-spending-is-much-larger-and-more-sustainable-than-it-seems/ (accessed 24 May 2019).

70

 See The Military Balance 117, no. 1 (2017) (see note 62), 66. Specifically, the authors of the Military Balance speak of a “temporary conventional superiority” of Russia in certain geographical areas such as the Baltic States.

71

 See The Military Balance 117, no. 1 (2017): 183–236 (184) (Chapter Five. Russia and Eurasia).

72

 The Military Balance 119, no. 1 (2019): 166–221 (175) (Chapter Five. Russia and Eurasia).

73

 See Russian Military Capability in a Ten-Year Perspective 2016, ed. Gudrun Persson (Stockholm: Swedish Defence Research Agency [FOI], December 2016), 3, https://www.foi.se/rest-api/report/FOI-R--4326--SE (accessed 6 May 2019).

74

 See The Military Balance 117, no. 1 (2017) (see note 71), S. 184, 188; Keir Giles, Assessing Russia’s Reorganized and Re­armed Military (Washington, D.C.: Carnegie Endowment for International Peace, 3 May 2017), 9, https://carnegieendow ment.org/files/5.4.2017_Keir_Giles_RussiaMilitary.pdf (accessed 21 May 2019).

75

 See Stephan Frühling and Guillaume Lasconjarias, “NATO, A2/AD [Anti-Access/Area-Denial] and the Kaliningrad Challenge”, Survival 58, no. 2 (2016): 95–116 (96).

76

 The S400 system can be directed against manned and unmanned missiles as well as ballistic missiles and cruise missiles, and has a range of approximately 400 km. It can thus cover the airspace from Kaliningrad to Riga, Vilnius or Warsaw as well as parts of Estonia.

77

 See The Military Balance 118, no. 1 (2018): 169–218 (174) (Chapter Five. Russia and Eurasia).

78

 See “Russia Deploys S-400 Missile Defense in Kaliningrad”, Baltic News Network, 7 April 2012, https://bnn-news.com/russia-deploys-s-400-missile-defense-kaliningrad-57349 (accessed 6 May 2019); Gareth Davies, Infomap. In Strike Range: Russian Weapon Systems in Kaliningrad (London, March 2017), https://www.ecfr.eu/article/commentary_kalinin grad_from_boomtown_to_battle_station_7256 (accessed 21 May 2019).

79

 Initially, the installation was only temporary as part of training exercises, but it has subsequently been made per­manent. See “Russland bestätigt Iskander-Raketen in Kaliningrad”, Frankfurter Allgemeine Zeitung (online), 4 May 2018, https://www.faz.net/aktuell/politik/ausland/nach-langer-geheimhaltung-russland-bestaetigt-iskander-raketen-in-kaliningrad-15574438.html (accessed 6 May 2019). The Iskander-M has a maximum range of 500 km and could thus reach Tallinn, Riga, Vilnius, Warsaw or Berlin. See Davies, Infomap (see note 78); Ian Williams, CSIS [Center for Strategic and International Studies] Missile Defense Project. The Russia-NATO A2AD Environment (Washington, D.C.: CSIS, 3 January 2017), https://missilethreat.csis.org/russia-nato-a2ad-environment/ (accessed 6 May 2019).

80

 See CSIS, SS-26 (Iskander) (Washington, D.C., 13 May 2019), https://missilethreat.csis.org/missile/ss-26/ (accessed 21 May 2019).

81

 The Military Balance 118, no. 1 (2018) (see note 77), 174.

82

 See The Military Balance 119, no. 1 (2019) (see note 72), 174.

83

 These authors are frequently ex-military or former members of the US administration. See, e.g., Billy Fabian, Mark Gunzinger, Jan van Tol, Jacob Cohn and Gillian Evans, Strengthening the Defense of NATO’s Eastern Frontier (Washington, D.C.: Center for Strategic and Budgetary Assessments [CSBA], 13 March 2019), https://csbaonline.org/research/publications/ strengthening-the-defense-of-natos-eastern-frontier (accessed 24 May 2019); Alexander R. Vershbow and Philip M. Breedlove, Permanent Deterrence: Enhancements to the US Military Presence in North Central Europe (Washington, D.C.: Atlantic Council, February 2019), https://www.atlanticcouncil.org/ publications/reports/permanent-deterrence (accessed 24 May 2019).

84

 See Shlapak and Johnson, Reinforcing Deterrence (see note 18), 1.

85

 Ibid.

86

Scott Boston et al., Assessing the Conventional Force Imbalance in Europe. Implications for Countering Russian Local Superiority, Research Report (Santa Monica: RAND Corporation, 2018), 8, https://www.rand.org/content/dam/rand/pubs/research_reports/RR2400/RR2402/RAND_RR2402.pdf (accessed 20 May 2019).

87

 By 2023 the German Ministry of Defence aims to be able to fully equip a tank brigade and make it operational, without it having to borrow material from other parts of the Bundeswehr. See Gutschker, “Die NATO muss schneller werden” (see note 64).

88

 See Boston et al., Assessing the Conventional Force Imbalance (see note 86), 10f.

89

 Von Hlatky, “American Alliances and Extended Deterrence” (see note 5), 7f.

90

 See DoD, Nuclear Posture Review Report (Washington, D.C., April 2010), https://dod.defense.gov/Portals/1/features/ defenseReviews/NPR/2010_Nuclear_Posture_Review_Report. pdf (accessed 21 May 2019).

91

 “Secure second strike capability” refers to the capability of a nuclear-weapons state to retaliate with nuclear weapons in the event of a nuclear atack on its territoy.

92

 See Oliver Thränert, “Tiefe Krise der atomaren Rüstungskontrolle. Ein Erfolgsrezept aus dem Kalten Krieg ist zu Unrecht in Vergessenheit geraten, Neue Zürcher Zeitung, 30 October 2018.

93

 See DoD, Nuclear Posture Review Report, 2010 (see note 90), 27.

94

 Hans M. Kristensen and Robert S. Norris, “Russian Nuclear Forces, 2018”, Bulletin of the Atomic Scientists 74, no. 3 (2018): 185–95 (191).

95

 Ibid., 190.

96

 On the modernisation of Russian nuclear short-range missiles, see ibid., 192.

97

 In its final declaration at the Brussels Summit in July 2018, NATO condemned Russia’s “irresponsible and aggressive nuclear rhetoric”: NATO, Brussels Summit Declaration. Issued by the Heads of State and Government Participating in the Meeting of the North Atlantic Council in Brussels (Brussels, 11–12 July 2018), https://www.nato.int/cps/en/ natohq/official_texts_156624.htm (accessed 21 May 2019).

98

 The US is focusing especially on the modernisation of non-strategic weapons that Russia can deploy with air-to-ground missiles, short-range ballistic missiles, bombers, ships and submarines. See DoD, Nuclear Posture Review, 2018 (see note 39), 52.

99

 See Jakob Hedenskog et al., “Russian Security Policy”, in Russian Military Capability, ed. Persson (see note 73), 97–132 (111).

100

 A frequently cited, albeit older, example is the threat made by the then Russian ambassador to Denmark, Mikhail Vanin, in spring 2015, that Danish warships would become the target of Russian nuclear weapons if they joined NATO’s missile defence. See Teis Jensen, Adrian Croft and Peter Graff, “Russia Threatens to Aim Nuclear Missiles at Denmark Ships If It Joins NATO Shield”, Reuters (online), 22 March 2015, https://www.reuters.com/article/us-denmark-russia/russia-threatens-to-aim-nuclear-missiles-at-denmark-ships-if-it-joins-nato-shield-idUSKBN0MI0ML20150322 (accessed 7 May 2019).

101

 See Kristensen and Norris, “Russian Nuclear Forces, 2018” (see note 94), 185.

102

 See DoD, Nuclear Posture Review, 2018 (see note 39), 30.

103

 See Bruno Tertrais, “Russia’s Nuclear Policy. Worrying for the Wrong Reasons”, Survival 60, no. 2 (2018): 33–44 (37).

104

 See Kristin ven Bruusgaard, “The Myth of Russia’s Lowered Nuclear Threshold”, War on the Rocks (online), 22 September 2017, https://warontherocks.com/2017/09/the-myth-of-russias-lowered-nuclear-threshold/ (accessed 7 May 2019).

105

 For a corresponding assessment, see Kristensen and Norris, “Russian Nuclear Forces, 2018” (see note 94), 187.

106

 The Military Balance 114, no. 1 (2014): 31-58 (54ff.) (Chapter Three: North America); The Military Balance 119, no. 1 (2019): 28-65 (59ff. ) (Chapter Three: North America); The Military Balance 117, no. 1 (2017) 1, p. 27-62 (58ff.) (Chapter Three: North America). The data refer to “deployments”, in which the authors of Military Balance include both permanently stationed troops and operational deployments. The numbers include US presence in all European countries, in­cluding non-NATO countries such as the Ukraine. The presence of the USA in Israel was not counted, although the country belongs to the area of operation of the European Command of the USA (EUCOM).

107

 The Military Balance 114, no. 1 (2014) (see note 106), S. 54ff; The Military Balance 119, no. 1 (2019) (see note 106), 59ff.

108

 “Amerika verlegt zusätzliche Soldaten nach Deutschland”, Frankfurter Allgemeine Zeitung (online), 7 September 2018, https://www.faz.net/aktuell/politik/inland/amerika-verlegt-zusaetzliche-soldaten-nach-deutschland-15776749.html (accessed 23 May 2019).

109

 USEUCOM, 2018 European Reassurance Initiative (ERI) Fact Sheet (Stuttgart, 28 June 2017); Pat Towell and Aras D. Kazlauskas, The European Deterrence Initiative [EDI]: A Budgetary Overview, CRS In Focus (Washington, D.C.: CRS, 8 August 2018), 1, https://fas.org/sgp/crs/natsec/IF10946.pdf (accessed 23 May 2019); Office of the Under Secretary of Defense (Comptroller), European Deterrence Initiative. Department of Defense Budget Fiscal Year 2020 (Washington, D.C., March 2019), 17, https://comptroller.defense.gov/Portals/45/Documents/defbudget/fy2020/fy2020_EDI_JBook.pdf (accessed 25 May 2019).

110

 USEUCOM, FY 2020 European Deterrence Initiative (EDI) Fact Sheet (Stuttgart, March 2019).

111

 U.S. Army Europe, Atlantic Resolve Fact Sheet (Wiesbaden, 6 June 2018), https://www.eur.army.mil/Newsroom/Fact-Sheets-Infographics/Fact-Sheet-Article-View/Article/1451471/ atlantic-resolve-fact-sheet/ (accessed 20 May 2019). The US-based Army Brigade, which was transferred to Europe for nine months, complements the two brigades stationed permanently in Germany and Italy, so that a total of three are now located in Europe.

112

 See U. S. Army Europe, Fact Sheet: Atlantic Resolve Armored Rotation (Wiesbaden, 11 January 2019), https://www.eur. army.mil/Portals/19/documents/Fact%20Sheets/1IDArmor RotationFactSheet.pdf (accessed 20 May 2019).

113

 See U.S. Army Europe, Atlantic Resolve Fact Sheet (see note 111).

114

 Office of the Under Secretary of Defense (Comptroller), European Deterrence Initiative, 2019 (see note 109), 1.

115

 See U. S. Army Europe, Fact Sheet. Army Prepositioned Stock (Wiesbaden, 13 September 2018), https://www.eur. army.mil/Portals/19/documents/FactSheets/APSFactSheet.pdf (accessed 20 May 2019).

116

 See USEUCOM, 2018 European Deterrence Initiative (EDI) Fact Sheet (Stuttgart, 2 October 2017).

117

 Office of the Under Secretary of Defense (Comptroller)/Chief Financial Officer, Defense Budget Overview. Fiscal Year 2020 Budget Request (Washington, D.C., 2019), 6–8, https://comptroller.defense.gov/Portals/45/Documents/defbudget/fy2020/fy2020_Budget_Request_Overview_Book.pdf (accessed 23 May 2019).

118

 For an overview of NATO decisions since 2014, see Table 7 “NATO transformation 2014-19”; The Military Balance 119, no. 1 (2019): 66-165 (70-71) (Chapter Four: Europe).

119

 NATO, NATO’s Enhanced Forward Presence (Brussels, February 2019), https://www.nato.int/nato_static_fl2014/ assets/pdf/pdf_2019_02/20190213_1902-factsheet_efp_en.pdf (accessed 12 June 2019).

120

 See USEUCOM, 2019 European Deterrence Initiative (EDI) Fact Sheet (Stuttgart, 2019), https://www.eucom.mil/media-library/document/36242/2019-edi-fact-sheet (accessed 23 May 2019).

121

 See The Military Balance 119, no. 1 (2019) (see note 118), 69.

122

 See Frühling and Lasconjarias, “NATO, A2/AD and the Kaliningrad Challenge” (see note 75), 109.

123

 See John Vandiver, “USAFE [U. S. Air Forces in Europe] Chief: Military Doing ‘360-degree’ Review of Basing in Europe”, Stars & Stripes (online), 25 July 2018, https://www. stripes.com/news/usafe-chief-military-doing-360-degree-review-of-basing-in-europe-1.539414 (accessed 7 May 2019). One of the locations is the Estonian air force base Ämari. See Evan Parker, USAFE Celebrates First Completed EDI-Funded Project (U.S. Air Forces in Europe – Air Forces Africa, 19 October 2018), https://www.usafe.af.mil/News/Article-Display/Article/ 1665483/usafe-celebrates-first-completed-edi-funded-project/ (accessed 23 May 2019).

124

 See William Howard, “Crews at RAF [Royal Air Force] Lakenheath Clear the Way for First Permanent US F‑35 Jet Campus in Europe”, Stars & Stripes (online), 21 March 2019, https://www.stripes.com/news/crews-at-raf-lakenheath-clear-the-way-for-first-permanent-us-f-35-jet-campus-in-europe-1.573635 (accessed 7 May 2019).

125

 See Richard Komurek, F‑22 Raptors Deploy to Europe (Ramstein Air Base, 20 October 2017), https://www.usafe. af.mil/News/Article-Display/Article/1348765/f-22-raptors-deploy-to-europe/ (accessed 23 May 2019).

126

 See USEUCOM, House Armed Services Committee Hearing (see note 35).

127

 Office of the Under Secretary of Defense (Comptroller), European Deterrence Initiative, 2019 (see note 109), 18.

128

 The Military Balance 115, no. 1 (2015): 17–20 (17) (Hybrid Warfare: Challenge and Response).

129

 See Andrew Radin, Hybrid Warfare in the Baltics. Threats and Potential Responses (Santa Monica: RAND Corporation, 2017), 6, https://www.rand.org/content/dam/rand/ ubs/research_reports/RR1500/RR1577/RAND_RR1577.pdf (accessed 23 May 2019).

130

 See John R. Deni, “NATO’s Presence in the East: Necessary but Still Not Sufficient”, War on the Rocks (online), 27 June 2018, https://warontherocks.com/2018/06/natos-presence-in-the-east-necessary-but-still-not-sufficient/ (accessed 7 May 2019). The EDI’s draft budget for 2019 provides resources to the amount of US$10 million for “information operations”. However, the EDI’s focus is on classical conventional reassurance. See Office of the Under Secretary of Defense (Comptroller), European Deterrence Initia­tive. Department of Defense Budget Fiscal Year 2019 (Washington, D.C., February 2018), 3, https://comptroller.defense. gov/Portals/45/Documents/defbudget/fy2019/fy2019_EDI_ JBook.pdf (accessed 12 June 2019).

131

 See United States Senate, Hearing to Receive Testimony (see note 47), 21.

132

 See The Military Balance 115, no. 1 (2015) (see note 128), 18.

133

 DoD, Nuclear Posture Review, 2018 (see note 39), V.

134

 NATO, Brussels Summit Declaration, 2018 (see note 97).

135

 See DoD, Nuclear Posture Review, 2018 (see note 39), 48ff.

136

 As part of the so-called SNOWCAT-Mission: Support of Nuclear Operations With Conventional Air Tactics. See Hans M. Kristensen, NATO Nuclear Exercise Underway With Czech and Polish Participation (Washington, D. C.: Federation of American Scientists, 17 October 2017), https://fas.org/blogs/security/ 2017/10/steadfast-noon-exercise/ (accessed 23 May 2019).

137

 See DoD, Nuclear Posture Review, 2018 (see note 39), 48.

138

 Ibid, 31.

139

 Ibid., 52ff.

140

 Ibid., 54.

141

 Ibid., 23.

142

 Wolfgang Richter, Erneuerung der nuklearen Abschreckung. Die USA wollen nukleare Einsatzoptionen und globale Eskalations­dominanz stärken, SWP-Aktuell 15/2018 (Berlin: Stiftung Wissenschaft und Politik, March 2018), 6, https://www.swp-berlin.org/fileadmin/contents/products/aktuell/2018A15_ rrw.pdf (accessed 7 May 2019) (this author’s translation).

143

 See Megan Keller, “Russian Official: Trump With­drawal from Arms Control Treaty Form of ‘Blackmail’”, The Hill (online), 21 October 2018, https://thehill.com/policy/international/412433-russian-official-trump-removing-us-from-arms-control-treaty-very (accessed 7 May 2019).

144

 See Karoun Demirjian, “GOP Lawmakers Criticize Trump's Decision to Withdraw from Nuclear Arms Treaty”, Washington Post (online), 21 October 2018. In 2017, Republican senators and House representatives led by Tom Cotton (Senate) and Mike Rogers (House of Representatives) proposed a bill - somewhat misleadingly called the “INF [Intermediate-Range Nuclear Forces] Treaty Preservation Act” - which included funding for the development of a mobile land-based cruise missile. See Tom Cotton, p.430 - 115th Con­gress (2017-2018): Intermediate-Range Nuclear Forces (INF) Treaty Preservation Act of 2017 (Washington, D.C., 16 February 2017), https://www.congress.gov/bill/115th-congress/senate-bill/430 (accessed 23 May 2019).

145

 See DoD, Nuclear Posture Review, 2018 (see note 39), 10.

146

 See Thomas Gutschker, “Amerika plant kein Wett­rüsten”, Frankfurter Allgemeine Sonntagszeitung, 10 February 2019.

147

 The different national perspectives on the USA can also be shaped by the respective domestic political conditions, historical experiences or political cultures. However, these factors are not analysed in the ­present study.

148

 Ministry of National Defence, Republic of Poland, Proposal for a U. S. Permanent Presence in Poland (Warsaw, 2018), 3f., https://g8fip1kplyr33r3krz5b97d1-wpengine.netdna-ssl.com/wp-content/uploads/2018/05/Proposal-for-a-U.S.-Permanent-Presence-in-Poland-2018.pdf (accessed 23 May 2019); Edyta Żemła and Kamil Turecki, “Poland Offers US up to $2B for Permanent Military Base”, Politico.eu (online), 27 May 2018, https://www.politico.eu/article/nato-poland-offers-us-up-to-2-billion-for-permanent-american-military-base/ (accessed 7 May 2019).

149

 On the corresponding discussion in Lithuania, see Ben Wolfgang, “Lithuania Sees U.S. Military as Solution to Rus­sian Menace. Defense Minister: Deployment Could Deter Putin”, Washington Times, 15 June 2018.

150

 Author interviews with diplomatic representatives from Estonia, Latvia and Lithuania in July/August 2018.

151

 See Sebastian Sprenger, “Lithuania Is First Baltic Nation to Sign US Defense-cooperation Pact”, Defense News (online), 3 April 2019, https://www.defensenews.com/global/ europe/2019/04/03/lithuania-is-first-baltic-nation-to-sign-us-defense-cooperation-pact/ (accessed 24 May 2019).

152

 Quoted in Gregory Hellman, “Congress Pressing Trump to Station More Troops in Europe”, Politico (online), 11 June 2018.

153

 See Konstantin Eggert, “Angela Merkel Faces Suspicion in Baltics”, Deutsche Welle (online), 13 September 2018, https://p.dw.com/p/34lCD (accessed 7 May 2019).

154

  Martin Zapfe, “Deterrence from the Ground Up. Understanding NATO’s Enhanced Forward Presence”, Survival 59, no. 3 (2017): 147–60 (153f.).

155

 Quoted in “Estonia Calls for Deployment of US Troops, Patriot Missiles”, Euractiv (online), 5 April 2018, https://www. euractiv.com/section/defence-and-security/news/estonia-calls-for-deployment-of-us-troops-patriot-missiles/ (accessed 23 May 2019).

156

 See Linas Jegelevičius, “Baltics Want Faster US Decisions on the Region’s Air Defence”, Baltic News Network, 9 March 2018, https://bnn-news.com/baltics-want-faster-us-decisions-on-the-region-s-air-defence-181421 (accessed 7 May 2019); “Estonia Calls for Deployment of US Troops, Patriot Missiles” (see note 155); Aaron Mehta, “Estonia Eyes Mid-range Air Defense Systems to Rectify NATO ‘Oversight’”, Defense News (online), 12 September 2018, https://www. defensenews.com/global/europe/2018/09/12/estonia-eyes-mid-range-air-defense-systems-to-rectify-nato-oversight/ (accessed 7 May 2019).

157

 See Jegelevičius, “Baltics Want Faster US Decisions” (see note 156).

158

 ”Air Policing” is a NATO mission to monitor and protect the airspace of allies who do not have the national capabilities to do so. These include the three Baltic countries as well as Albania, Luxemburg, Iceland and Slovenia.

159

 See Aaron Mehta, “NATO’s Air Defense Problem: Maintaining the Peace vs. Securing the Eastern Flank”, Defense News (online), 19 July 2018, https://www.defensenews. com/smr/nato-priorities/2018/07/19/natos-air-defense-problem-maintaining-the-peace-vs-securing-the-eastern-flank/ (accessed 23 May 2019).

160

 This does not, however, apply unreservedly to all east­ern NATO states. Czech President Miloš Zeman, for example, has been accused of taking a pro-Russian stance in foreign policy. See Rick Lyman, “Eastern Europe Cautiously Welcomes Larger U.S. Military Presence”, International New York Times, 2 February 2016. Some of the assessments in this section of the study are based on personal interviews the author had with representatives of the three Baltic republics, Poland and Romania in Berlin in the summer of 2018.

161

 See Shawn Snow, “Marines Are on Sweden’s Coast Preparing for Largest NATO Exercise as Russia Grumbles”, Marine Corps Times, 4 September 2018, https://www.marine corpstimes.com/news/your-marine-corps/2018/09/04/marines-are-on-swedens-coast-preparing-for-largest-nato-exercise-as-russia-grumbles/ (accessed 7 May 2019).

162

 See Aaron Mehta, “Finland, Sweden and US Sign Trilateral Agreement, with Eye on Increased Exercises”, Defense News (online), 9 May 2018, https://www.defense news.com/training-sim/2018/05/09/finland-sweden-and-us-sign-trilateral-agreement-with-eye-on-increased-exercises/ (accessed 7 May 2019).

163

 See Pauli Järvenpää, The United States, Finland and Sweden: A Trilateral Statement of Defense Interest, ICDS Blog 2018 (Tallinn: International Centre for Defence and Security [ICDS] Estonia, 25 May 2018), https://icds.ee/the-united-states-finland-and-sweden-a-trilateral-statement-of-defense-interest/ (accessed 23 May 2019).

164

 See, e.g., Ministry of National Defence of the Republic of Lithuania, National Security Strategy of the Republic of Lithuania (Vilnius, 2017), 4, https://kam.lt/download/57457/2017-nacsaugstrategijaen.pdf (accessed 23 May 2019).

165

 See Manuel Lafont Rapnouil, Tara Varma and Nick Witney, Eyes Tight Shut: European Attitudes towards Nuclear Deterrence, Flash Scorecard (London: European Council on Foreign Relations [ECFR], December 2018), 4–5, https://www.ecfr.eu/page/-/NUCLEAR_WEAPONS_FLASH_ SCORECARD.pdf (accessed 23 May 2019).

166

 Ibid., 7.

167

 See Viljar Veebel, “(Un)Justified Expectations on Nuclear Deterrence of Non-nuclear NATO Members. The Case of Estonia and Latvia?”, Defense & Security Analysis 34, no. 3 (2018): 291–309 (300).

168

 For the corresponding Latvian position, see Ashish Kumar Sen, “Nuclear Component Must Be Part of NATO’s Deterrence Policy in Europe’s East, Says Latvia’s Foreign Minister” (Washington, D.C.: Atlantic Council, 26 February 2016), http://www.atlanticcouncil.org/blogs/new-atlanticist/ nuclear-component-must-be-part-of-nato-s-deterrence-policy-in-europe-s-east-says-latvia-s-foreign-minister (accessed 23 May 2019).

169

 See Veebel, “(Un)Justified Expectations on Nuclear Deterrence” (see note 167), 299.

170

 See Polish Institute of International Affairs (PISM), The Central and Eastern European Resource Collection on Nuclear Issues. Estonia (Warsaw, 28 April 2015), 2, https://www.pism.pl/files/?id_plik=19768 (accessed 23 May 2019). See also Liviu Horovitz, “Why Do They Want American Nukes? Central and Eastern European Positions Regarding US Nonstrategic Nuclear Weapons”, European Security 23, no. 1 (2014): 73–89 (74f.): “None of the CES [Central Eastern States’] experts interviewed for this article could outline a tactical scenario in which these weapons could serve as a reliable deterrent.”

171

 See Andrew Somerville et al., Poland, NATO and Non‑Strategic Nuclear Weapons in Europe, Occasional Paper (Euro­pean Leadership Network, February 2012), 13, https://www.europeanleadershipnetwork.org/wp-content/uploads/2017/12/Poland.-NATO-and-NSNW-in-Europe.pdf (accessed 23 May 2019); Stephan Frühling and Andrew O’Neil, “Nuclear Weapons, the United States and Alliances in Europe and Asia. Toward an Institutional Perspective”, Contemporary Security Policy 38, no. 1 (2017): 4–25 (16).

172

 See Łukasz Kulesa, Polish and Central European Priorities on NATO’s Future Nuclear Policy, Nuclear Policy Paper 2/2010 (Washington, D.C., London and Hamburg: Arms Control Association [ACA], British American Security Information Council [BASIC], Institute for Peace Research and Security Policy at the University of Hamburg [IFSH], November 2010), 9, https://www.basicint.org/wp-content/uploads/2018/06/ Nuclear_Policy_Paper_No_2.pdf (accessed 8 May 2019).

173

 See “Poland Denies Considering Request for Nuclear Weapons” (Associated Press), Military Times (online), 6 December 2015, https://www.militarytimes.com/news/your-military/2015/12/06/poland-denies-considering-request-for-nuclear-weapons/ (accessed 8 May 2019); Kingston Reif, Poland Backs Away From Nuclear Sharing (Washington, D.C.: Arms Control Association, January/February 2016), https:// www.armscontrol.org/ACT/2016_0102/News-Briefs/Poland-Backs-Away-From-Nuclear-Sharing (accessed 23 May 2019).

174

 See Jan Puhl and Markus Becker, “Aus für INF-Abkommen: Polens Außenminister für US-Atomwaffen in Europa”, Spiegel Online, 1 February 2019, https://www. spiegel.de/politik/ausland/inf-abkommen-polnischer-aussenminister-fordert-us- atomraketen-in-europa-a-1251157.html (accessed 21 May 2019).

175

 See Gutschker, “Amerika plant kein Wettrüsten” (see note 146).

176

 See Rapnouil et al, Eyes Tight Shut (see note 165), 6.

177

 See Veebel, “(Un)Justified Expectations on Nuclear Deterrence” (see note 167), 304; Kulesa, Polish and Central European Priorities (see note 172), 7.

178

 Personal background conversation with the author.

179

 On the issue of the credibility of British and French nuclear guarantees, see Rapnouil et al, Eyes Tight Shut (see note 165), 10.

180

 See Konrad Schuller, “‘Es gilt, dass Frau Merkel für uns das Beste wäre’. Interview mit PiS-Chef Jarosław Kaczyński”, Frankfurter Allgemeine Zeitung (online), 7 February 2017, https://www.faz.net/aktuell/politik/ausland/kaczynski-wuenscht-sich-fuer-polen-einen-sieg-merkels-14859766.html (accessed 8 May 2019).

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