NATO Without the US: Could Europe Actually Defend Itself?
As Washington’s commitment to the alliance falters, European powers face a difficult choice over the future of their security landscape.
There is a particular kind of dependency that only becomes visible when it is threatened. For eight decades, European security was underwritten by an American commitment whose durability was treated, in most capitals, as close to a law of nature. NATO was the architecture, but the United States was the foundation on which it stood.
That assumption collapsed with speed in 2025. When US Secretary of Defence Pete Hegseth said in February that ‘now is the time to invest because you [European NATO members] can’t make an assumption that America’s presence will last forever’ (POLITICO, 2025), he was not announcing a policy change so much as making explicit what the Trump administration had long been signalling: these security guarantees are conditional, transactional, and subject to revision.
That tone has only hardened since. In March 2026, Trump declared on Truth Social that ‘without the U.S.A., NATO IS A PAPER TIGER’, directing the comment at allies who declined to join American operations in the Strait of Hormuz (The Hill, 2026). The willingness of a sitting president to publicly degrade the alliance he nominally leads tells its own story about the durability of the American commitment. That NATO’s own Secretary-General felt compelled to wish ‘good luck’ to those who believe Europe can defend itself without the US (NPR, 2026) speaks to how far the ground has shifted. While accurate as a description of the present, this sentiment remains misleading as a guide to the possible.
A Gap in Strategy, Not Just Hardware
It is tempting to attribute Europe’s defence deficit to a spending shortfall – a problem of political will which, once resolved, unlocks the hardware. This understanding is partly true but ultimately incomplete. The core of what the United States provides is not simply volume, but integration capacity, including the intelligence architecture, satellite communications, and precision strike capability. Europe was never asked to develop this technology precisely because America developed it for them.
This situation is the structural legacy of the Cold War. The result, after 75 years, is a Europe with sophisticated conventional forces in some states, limited fifth-generation air power, and a nuclear deterrent that resides with two NATO member states but is not extended, in any formal or operational sense, to the alliance. A May 2025 IISS assessment estimates replacing US capabilities would cost roughly $1 trillion over 25 years (IISSa, 2025). That figure understates the problem because hardware can be bought, while the knowledge which makes this hardware effective cannot. What the United States brings is not just capability but a common operating language, one which allows allied forces to coordinate quickly under pressure.
A credible European defence is not the sum of national capabilities. It is those capabilities integrated under unified command, operating according to shared doctrine, with the political authority to act collectively in a crisis. None of that exists at scale. Hungary and Slovakia remain actively hostile to the idea of a European security architecture oriented against Russia. Any structure that excludes them is geographically incoherent, whilst any structure that includes them is politically compromised.
The nuclear question illustrates the depth of the political difficulty. The Northwood Declaration of July 2025, committing France and Britain to coordinate nuclear policy and operations, is the biggest step in Anglo-French defence cooperation in decades (IISSb, 2025). But the IISS is right to caution that a European deterrent would not be a quick fix (IISSc, 2025) Broadening any deterrent beyond the two existing nuclear states raises questions that no government has been willing to answer in public, namely whose finger is on which button, and what democratic mandate exists for nuclear decisions made at the European rather than the national level?
A Political Question Dressed as a Military One
The rearmament now underway across Europe is the most consequential since the 1950s. Germany’s constitutional change will not be easily reversed. Poland’s investment, over 4% of GDP (the highest in NATO) reflects a culture reshaped by proximity to the front line. Qualitatively, in naval and cyber domains, Europe already performs at a high level without full American oversight, as seen in the NATO spring 2025 North Atlantic operations, which ran with zero US ships in the task force (Atlantic Council, 2025).
But NATO secretary general Mark Rutte’s scepticism rests on something harder to overcome than a spending gap. Broadly speaking, there are two models available to Europe. The first is a reformed NATO with a much larger European contribution, in which American participation continues but no longer dominates. The second is genuine strategic autonomy: a continent that is capable of deterring and defeating a Russian conventional attack without American assistance. The first is achievable within a decade, with sustained political will. The second requires not just procurement budgets but a deepening of European political integration across decades, which most governments have not yet committed to pursuing.
What is clear is that the era in which Europe could defer this choice has ended. The American guarantee that made the choice unnecessary is conditional. The threat that makes the question urgent is not on the retreat. And the political momentum, in Berlin, Warsaw, Paris, and elsewhere, is running in the right direction. The question is whether it is running fast enough, and whether it is running in the same direction across all 27 capitals.
Bibliography
Atlantic Council (2025) Immediate Steps That Europe Can Take to Enhance Its Role in NATO Defense. Washington DC: Atlantic Council. https://www.atlanticcouncil.org/in-depth-research-reports/issue-brief/immediate-steps-that-europe-can-take-to-enhance-its-role-in-nato-defense/
Hegseth, P. (2025) Remarks at NATO Defence Ministers’ Meeting. Cited in: ‘America’s military presence in Europe “not forever”, Hegseth warns’, POLITICO, February 2025. https://www.politico.eu/article/america-military-presence-europe-not-forever-us-pete-hegseth-warns/
International Institute for Strategic Studies (2025a) Defending Europe Without the United States: Costs and Consequences. https://www.iiss.org/research-paper/2025/05/defending-europe-without–the-united-states-costs-and-consequences/
International Institute for Strategic Studies (2025b) ‘The Northwood Declaration: UK–France nuclear cooperation and a new European strategic backstop.’ https://www.iiss.org/publications/strategic-comments/2025/09/the-northwood-declaration-uk-france-nuclear-cooperation-and-a-new-european-strategic-backstop/
International Institute for Strategic Studies (2025c) ‘A new European nuclear deterrent would not be a quick fix’, IISS Online Analysis, May. https://www.iiss.org/online-analysis/online-analysis/2025/05/a-new-european-nuclear-deterrent-would-not-be-a-quick-fix/
NPR (2026) ‘NATO chief wishes “good luck” to those who think Europe can defend itself without US help’, 27 January. https://www.npr.org/2026/01/27/nx-s1-5689791/nato-chief-europe-defense-us
Trump, D. (2026) ‘NATO is a paper tiger without the U.S., Trump says’, The Hill, 20 March. https://thehill.com/homenews/administration/5793172-trump-nato-paper-tiger/
