Marco Overhaus

US Defence Policy: Between Isolationism and the Pursuit of Dominance

Contradictions in Washington Demand a Clear Response from Europe

SWP Comment 2026/C10, February 2026

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DOI: 10.18449/2026C10

(English version of SWP‑Aktuell 6/2026)

US defence policy is characterised by contradictions that are on display once again in the Trump administration’s latest strategy documents. The reasons for this go far beyond the president’s erratic behaviour. At the core lies the unanswered question of how the United States should deal with the loss of global dominance. For Europe, these contradictions present not only risks but also opportunities. But German and European decision-makers should not fall victim to the false hope that NATO in its current form will survive Trump’s second term in office.

US Defence Policy: Between Isolationism and the Pursuit of Dominance

Contradictions in Washington Demand a Clear Response from Europe

Marco Overhaus

Since Donald Trump returned to the White House in January 2025, there has been a high degree of uncertainty in Berlin and the capital cities of other US allies about the course of America’s defence and alliance policy. The signals coming both from the diplomatic and military apparatus in Washington and from the US Congress are often at odds with the impulses that drive the president. That much has become clear from American claims to ownership of Greenland. At the same time, the strategy documents recently published by the Trump administration leave many questions unanswered.

Strategic dissonance

The National Security Strategy of November 2025 (NSS 2025) differs in tone and partly in substance from the National Defense Strategy published in January 2026 (NDS 2026). The divergences can be attributed not least to the different authorship and purposes of the two documents. The NSS is drafted mainly by the White House and the National Security Council while the NDS is the responsibility of the Department of Defense. While both strategies reflect Trump’s political guidelines, the NSS places much greater emphasis on his domestic and ideological agenda. And while they both fundamentally underscore the importance of the United States’ alliances, the security strategy includes a sweeping verbal attack on liberal Europe – an attack that is directed, first and foremost, against the EU but also calls into question the values on which NATO has been based to date. The NDS 2026 provides no details about the size, orientation, deployment and stationing of US troops and military equipment in Europe or other regions of the world. This only increases the uncertainty about Washington’s alliance policy in the future.

The inconsistencies in American defence policy are particularly evident under Trump, but the reasons go much deeper than his behaviour. For a quarter of a century, the US has been struggling to find ways to deal with the end of the “unipolar moment”. The consequences of 11 September 2001, the overstretch of the subsequent “war on terror” and the rise of China as a major power pole have generated considerable uncertainty in Washington. Three different approaches have shaped the response to the loss of global dominance.

The first approach is based on an opportunistic use of military force. Here, the main aim is to demonstrate “strength” – both internally and externally – and to achieve short-term, narrowly defined goals. At the same time, military risks are to be minimised and protracted security-policy entanglements avoided. Classic examples are the drone and other “precision” strikes undertaken since 2001 as part of the war on terror, as well as the recent military strikes against alleged drug boats and the military operation to kidnap Venezuelan leader Nicolás Maduro.

The second approach – isolationism – is closely related to, but distinct from, the opportunistic approach. Isolationism, which is espoused not only by today’s MAGA movement, reflects the conviction that the costs of striving for global dominance far outweigh the benefits and that America should keep as far away as possible from international entanglements and alliances.

And the third approach is one of selective hegemony, which has important advocates, particularly in the defence apparatus. It aims to preserve American power and influence by investing heavily in the military, on the one hand, and concentrating on key strategic regions, on the other.

At times, the three approaches exist in parallel and, at other times, they are combined, as has recently been the case with the rediscovery of the “Western Hemisphere”. But when it comes to fundamental security policy issues, the contradictions between them are apparent. Isolationism and opportunism point to a departure from lasting alliances and partnerships and grant other major powers their own regional spheres of influence. Selective hegemony, on the other hand, is aimed at preventing Chinese and Russian dominance in Asia and Europe, respectively; thus, it requires at least a minimum level of acceptance and support from allies.

Rediscovery of the Western Hemisphere

Both the NSS 2025 and the NDS 2026 prioritise restoring US dominance in the “Western Hemisphere”. Trump’s revised edition of the Monroe Doctrine of 1823 refers to the entire area stretching from the southernmost tip of the American continent to the far north, including Greenland.

The return to 19th-century hemispheric thinking under Trump was by no means to be expected or self-evident. In the NSS of the first Trump administration (published in December 2017), the Western Hemisphere is not addressed until towards the end of the document; and, in terms of geographical priorities, it ranks fifth, followed only by Africa. Other US administrations of the post-Cold War era similarly regarded the Western Hemisphere as subordinate to Europe, Asia and the Middle East. To this day, the US has only a small military presence outside its own borders in the region. In Central and South America, including the Caribbean, it maintains a naval base in Guantanamo Bay, Cuba and the Soto Cano Air Base in Honduras. There are also small bases (known as cooperative security locations) in El Salvador and Curaçao. In Greenland, the US has significantly reduced its military presence since the end of the Cold War. Today, it has a single military base there – the Pituffik Space Base, which has some 100 personnel and a radar station for monitoring space.

Even at the outset of Trump’s second term, the geopolitical concept of the Western Hemisphere did not seem to be a top priority for the foreign and security policy of the new US administration. At least, that is what media reports on Defense Secretary Pete Hegseth’s Interim National Defense Strategic Guidance of spring 2025 (not publicly available) suggest. And the Western Hemisphere also played a minor role in Trump’s first budget request for the Pentagon, made in summer 2025.

In connection with the military operation in Venezuela to kidnap Nicolás Maduro and his wife, which was obviously prepared well in advance, the US has significantly increased its military presence in the Caribbean and the eastern Pacific. At one point, Operation Southern Spear comprised nearly 40 per cent of all ships deployed globally by the US Navy, according to the Center for Strategic and International Studies. However, it is not clear whether the goal is to establish a permanent presence, not least as that would entail significant reductions in other regions of the world, particularly Asia.

Trump’s rediscovery of the Western Hemisphere as an exclusive zone of US dominance is likely to be related, above all, to the intertwining of geopolitical and domestic political logics in this region. From a geopolitical perspective, it is a kind of “fallback strategy” against the backdrop of the US itself no longer seeing any possibility of remaining a globally dominant power, despite its still enormous defence budget.

In its own hemisphere, however, the US can continue to claim unchallenged supremacy. And it can do so with relatively little security and military risk. There is no military power in the region – let alone, nuclear power – that could pose a real threat to the United States. Furthermore, owing to geographical proximity, it is easier for the US to counter the presence of China or Russia in its own region than in Asia or Europe, respectively. Unlike in the Taiwan Strait, there is no arsenal of modern medium-range missiles that could seriously threaten US aircraft carriers.

The contradictions between the statements made by Trump and the impulses that drive him, on the one hand, and the signals being sent from other parts of the administration, on the other, are also evident with regard to the concept of the Western Hemisphere. For example, in connection with the military operation in Venezuela, the US president threatened Mexico – at least implicitly – and offended the United States’ northern neighbour, Canada, by fantasising about that country becoming the 51st state. By contrast, the NDS 2026 contains much more conciliatory statements about those two countries. Both Mexico and Canada are accorded “strong roles in hemispheric defense”. As regards Panama and Greenland, there is no mention of “ownership” but merely the insistence that the US retain military and economic access, which, at least in principle, is compatible with the territorial sovereignty of Panama and Denmark.

Isolationist impulses and opportunistic interventions

At the same time, the new focus on the Western Hemisphere follows a domestic political logic. In this geographical area, the quest for dominance can be linked to a political agenda that is particularly popular in MAGA circles and aims, above all, at protecting the country’s own borders: the pursuit of a tough migration policy and the fight against drug trafficking. There is also the promise to keep the cost of living in the US under control through cheap energy. Venezuela’s large oil reserves fit this narrative, even if it seems doubtful – at least in the short or medium term – that the US will benefit economically from their exploitation.

Furthermore, the reference to the concept of the Western Hemisphere is closely linked to homeland defence. It is, of course, nothing new that the US prioritises the protection of its own territory. What is new under Trump, however, is that the US military is to assume a prominent role both in border protection and, increasingly, in internal security – tasks that traditionally fall to other security agencies and authorities. This new approach is also reflected in the executive orders that Trump issued at the beginning of his second term. Irregular migration is identified, especially in Trump’s rhetoric, as a threat equivalent to a military invasion by hostile powers. This is seen as justifying the use of the military at the border and within the country.

In particular, the deployment of the National Guard in cities governed by Democrats – such as Los Angeles, Washington, D.C. and Chicago – has significantly inflamed the domestic political climate in the United States. Compared with the total size of the US armed forces, the number of soldiers mobilised for border protection and operations in American cities is negligible. The National Guard is both part of the US armed forces and a state militia. But Trump’s decision to deploy the organisation was significant politically because it put the US military at the centre of domestic disputes. And that conflicts with the basic principle that in a democracy, armed forces should be politically neutral.

Moreover, the decoupling of the protection of US territory from the military’s global engagement is much more extensive under Trump than under previous administrations. Earlier, Washington followed the maxim that protecting the American homeland did not begin at the United States’ external borders but required an alliance system on a global scale (as “shields of the republic”). The current Trump administration is guided by this notion to a much lesser extent.

The change in tack is particularly evident from the focus on nuclear deterrence for homeland defence in the NDS 2026. There is no mention in the strategy document of “extended nuclear deterrence”, which includes allies in Europe and Asia. A new Nuclear Posture Review could provide some clarity, but it remains unclear whether or when it will be forthcoming. According to the wording of NDS 2026, the plans for the “Golden Dome,” a massive expansion of the national missile defence system, are aimed, above all, at protecting the American heartland rather than strengthening the United States’ security commitments to its allies and partners.

Given the US president’s threatening gestures toward Venezuela and Iran, it is noteworthy that, in its strategy documents, the Trump administration rejects violent regime change and nation-building interventions. This is in harmony with the security policy leitmotifs of the MAGA movement in the wake of the US experience in Afghanistan and Iraq; and it is supported within the United States by a large majority across party lines.

Trump’s decisions to use military force in Iran (Operation Midnight Hammer), Venezuela and Nigeria are consistent with the opportunistic approach to US defence policy, which was by no means unfamiliar to previous US administrations. Under this approach, the US demonstrates strength when the expected benefits (including domestic political ones) are substantial and the military risks low. It is a way of acting that corresponds to Trump’s idea of strength and, like tariffs, can be used to exert pressure on other countries. But long-term security and military entanglements are to be avoided at all costs.

Selective pursuit of hegemony and the strategy of denial

The NDS 2026 makes it clear that the US does not want to limit itself to protecting its own heartland and dominating the Western Hemisphere. Rather, it wants to continue to exercise influence in other regions of the world as part of the pursuit of selective hegemony. From the Pentagon’s perspective, seeking supremacy in the Western Hemisphere does not explicitly mean granting China and Russia their own spheres of influence in Asia and Europe, respectively. At the same time, it is only China that the Pentagon considers to have the will and the ability to establish regional or, possibly even, global dominance.

The effort to deny China a hegemonic role in Asia has been described as the Strategy of Denial. Elbridge Colby described this strategy in detail several years ago in his influential book of the same name. As Under Secretary of Defense for Policy in the second Trump administration, he was instrumental in developing the NDS 2026.

The basic assumption of the Strategy of Denial is that the US no longer has the military capabilities to maintain global dominance. However, by shifting its foreign policy focus to Asia, it would still have the means to ensure a balance of power that serves American interests. To achieve such a balance, the US would continue to need considerable military capabilities and the support of its regional allies.

The Trump administration’s budget proposals to date reflect this security policy strategy. For example, the budget proposal for fiscal year 2026 included defence spending of nearly $ 1 trillion. According to the Pentagon, that is an approximately 13 per cent increase over the previous year. For fiscal year 2027, Defense Secretary Hegseth has promised to boost spending to $ 1.5 trillion. A key focus of the planned expenditures is large and expensive arms projects, of which Trump, too, is very fond. Among those projects is the next generation of (manned) fighter aircraft (project title “F‑47”), a significant expansion of the navy (“Golden Fleet”), including new battleships (project name “Trump class”), and the “Golden Dome” missile defence shield.

In addition, the US wants to invest heavily in building up its ammunition reserves as well as its AI and drone capabilities and further modernising its nuclear weapons arsenal. Overall, the planned expenditures signal the clear intention to continue preparing the US military for high-intensity warfare, especially against a peer competitor such as China. But the enormous increases in spending and the prioritisation of gigantic arms projects cannot be justified solely by the pursuit of dominance in the Western Hemisphere and the protection of US territory.

The fractures and contradictions in US defence policy under Trump are also clearly evident with regard to China. The defence of Taiwan plays a central role in the Strategy of Denial. As Colby explains in his book, Taiwan (together with the Philippines) must be considered the weakest link in the “anti-hegemonic” coalition against the People’s Republic. There are many signs that the island nation will continue to play an important role in US defence planning. Hegseth’s Interim National Defense Strategic Guidance reportedly regarded a possible attack on Taiwan as the key scenario to be taken into consideration when designing the mission, structure and capabilities of the US armed forces.

However, the recently published NDS makes no mention of Taiwan. It merely alludes to the fact that the US wants to preserve the ability to defend the first island chain, which includes Taiwan. Although the Indo-Pacific region is considered central to US interests in the NDS and China’s enormous arms buildup is viewed with great concern – as it was in previous US strategy documents – the tone towards Beijing is strikingly conciliatory, which testifies to an attempt to ease tensions. In its relations with China, Washington appears to be seeking de-escalation and “strategic stability”. And, overall, it seems that Trump’s policy towards Beijing is driven more by his trade agenda than by US geopolitical interests.

Europe: Secondary, but not irrelevant

As expected, Europe appears low down on the list of priorities included in the new defence strategy. Unlike China and its position in the Indo-Pacific, Russia is not considered capable of dominating the continent’s political and economic power centres. At the same time, it is emphasised that Russia’s nuclear arsenal and its underwater, space and cyber capabilities also pose a threat to US territory.

Consistent with the selective hegemony approach is Washington’s view that its allies in Europe carry the main responsibility for deterring Russia. But this also means that the US continues to rely heavily on NATO so that it can focus on its own priorities. Accordingly, the NDS 2026 emphasises that the Department of Defense will carry on playing a vital role in NATO. In this context, it is noteworthy that the defence strategy uses the term “burden-sharing”, which is established and widely accepted within the alliance, rather than the much more conflict-laden “burden-shifting”.

Nevertheless, the terminology deployed in the NDS, which is benevolent towards NATO and other alliances, clearly contradicts the rhetoric and actions of Trump, who is prepared to risk an open break with the alliance over his claim to US ownership of Greenland. It is also in contradiction with the ideologically aggressive tone of the NSS, which, among other things, warns about the prospect of “civilizational extinction” of Europe. According to that strategy, the foundations of the alliance are threatened, too, in the long term because the populations of some NATO countries are becoming predominantly “non-European”.

While there are key players in the defence complex and the US Congress who continue to appreciate the value of NATO, the situation for Ukraine is much more precarious. Trump’s penchant for an opportunistic approach to military deployment (maximising short-term benefits of a primarily domestic political nature and minimising security risks) raises doubts about whether any “security guarantees” to Ukraine would be viable should the Trump administration grant them as part of a ceasefire agreement with Russia.

Against the backdrop of all these contradictions, Berlin and other European capitals are focusing their attention on Washington’s actual defence posture and decisions about deployments in Europe. While the NDS 2026 provides no concrete information about the latter, there were rumours circulating in summer 2025 that Trump might reduce the American troop presence in Europe by up to 30 per cent. By contrast, the signals coming from Congress appear encouraging. In December 2025, with the support of both parties, the US legislature passed the National Defense Authorization Act, which, among other things, is intended to prevent a significant withdrawal of US troops (below the limit of 76,000). The law also reflects continued bipartisan support for Ukraine, although it provides for just $ 800 million in new military aid over the next two years.

It remains to be seen what concrete decisions the Trump administration will make in the coming weeks and months. A litmus test could be the deployment of US medium-range weapons in Germany, which was decided under Joe Biden, and, according to current plans, is to begin in 2026. Conservative voices in the US have criticised this deployment decision because they see it as essentially incompatible with the goal of reducing the role of the United States in European security. They argue that medium-range weapons are offensive weapons that would provoke Russia but not effectively deter it. However, from the perspective of the German government – both then and now – their deployment would not only send a signal of deterrence to Russia but also demonstrate the continued strength of the transatlantic alliance.

Outlook

Today’s complex situation presents both opportunities and risks for Europe and NATO. On the one hand, the contradictions mentioned above show that national interests continue to guide US defence policy in key areas. This means that even in the Trump era, there are certain limits to implementing radical changes, not least with regard to the US military presence in the world. In that sense, it is true that defence posture is “sticky”. In the event of a radical departure from NATO and a major troop withdrawal from Europe, Trump would have to reckon with domestic political opposition from the military apparatus and Congress. Trump’s retreat – verbally, at least – on Greenland and punitive tariffs at the World Economic Forum in Davos in January 2026 can likely be attributed to some extent to these domestic political factors.

On the other hand, all three approaches for dealing with the loss of global dominance – opportunism, isolationism and selective hegemony – raise doubts about the future role of the US as guarantor of European security. In any case, it is patently clear that Europe is slipping down America’s list of geopolitical priorities.

Donald Trump’s impulsive political style will further complicate matters over the next three years. This raises the question about whether Washington is, in fact, willing or able to reduce the US military presence in Europe in what US Ambassador to NATO Matthew Whitaker said in summer 2025 would be a planned, coordinated manner so that no capability gaps arise.

Thus, it is all the more important for NATO-Europe to counter the US strategic dissonance with a clear strategy of its own – one that aims at Europe assuming significantly more responsibility for its defence under a carefully drawn-up and ambitious plan. The chances are good that this will be achieved within NATO, because there are still important forces in the US defence establishment and Congress who have no interest in the disintegration of the alliance.

However, this realisation should not lead to a false sense of security, as was the case after Obama and Joe Biden had taken office. The United States is no longer sure of its own role in the world. Trump’s unpredictability will shape US policy for another three years, while the isolationism of the MAGA movement will outlast his second term.

Dr Marco Overhaus is Deputy Head of SWP’s The Americas Research Division.