The nuclear architecture underpinning European security was never designed to stand alone. Since 1949, it has rested on a single load-bearing pillar: the United States (U.S.). That pillar has become visibly unreliable and unpredictable. President Donald Trump's public questioning of NATO's (North Atlantic Treaty Organization) Article 5 collective defence guarantee, combined with explicit statements encouraging Russian aggression against allies who fail to meet spending targets (Lambert-Deslandes and Von Hlatky 2025, 682), has transformed what was once a theoretical debate into an urgent operational problem. Europe possesses two independent nuclear arsenals, first, France's Force de Frappe and second, the United Kingdom's (UK) Trident program; yet neither was designed to protect other states. That gap between existing capability and extended deterrence is the central vulnerability the NATO alliance has yet to seriously confront.

This brief argues that France and the UK must move beyond declaratory openness toward institutional commitment. A formal European nuclear consultative body, operating independently of U.S. authorization and structured to begin integrating French and British deterrents into a coherent European posture, is the only strategically rational response to disappearing U.S. guarantees. The window for building that architecture is narrowing. This brief neither argues for proliferation nor non-proliferation of nuclear weapons. Instead, it applies a realist lens to examine which tools Europe undeniably already possesses and analyzes how they can best be used to protect the NATO alliance and promote world peace in an unpredictable global order. 

The Problem: A Deterrence Architecture Built on a Disappearing Foundation

European security has long operated on an implicit bargain: non-nuclear states would forgo independent arsenals in exchange for the protection of the U.S. nuclear umbrella through NATO. Germany is the clearest case study of this European dilemma. Its nuclear renunciation, enshrined in the Nuclear Non-Proliferation Treaty (NPT) of 1975 and the Two-Plus-Four Treaty of 1990, was a carefully negotiated quid pro quo; it was not an unconditional moral commitment (Bunn 2006, 87–88). The permanence of U.S. protection was the enabling condition of the entire post-war European security settlement.

That condition no longer holds. As of March 2026, Trump has declared on Truth Social that the U.S. "no longer need, or desire, the NATO Countries' assistance" (Trump 2026). The Trump Administration's pattern of aggressive unilateralism, such as threats to annex Greenland (Adler 2026), suggestions that Canada become the "51st state" (Doyle et al. 2026), and the coercive use of economic pressure against allies (Dworkin et al. 2026) signals that proximity to the U.S. is no longer a guarantee of protection. Whether Washington will honour its commitments under Article 5, maintain its forward presence in Europe or preserve the credibility of its nuclear umbrella can no longer be assumed (Sutherland 2026).

This uncertainty coincides with a deteriorating threat environment. Russia maintains the world's largest nuclear arsenal at approximately 5,459 warheads (International Campaign to

Abolish Nuclear Weapons 2026), including an estimated 2,000 tactical nuclear weapons it views as an "offset to NATO's conventional superiority" (Fink 2026). Putin's "escalate to de-escalate" doctrine of threatening the limited use of nuclear weapons to avert conventional conflict has been applied as a live strategic framework throughout the war in Ukraine (Rosenbach et al. 2026,19; Arms Control Association 2025). NATO's Secretary General has warned that Russia could be ready to attack alliance territory within five years (Ibu 2025) and Germany projects a large-scale conventional war capability from Moscow by 2030 (Saradzhyan 2025). Against this timeline, the absence of a coherent European nuclear posture is a structural vulnerability.

Why Conventional Armament Cannot Fill the Gap

A natural response to U.S. unreliability is to accelerate conventional armament. Returning to the case study, Germany is projecting a defence budget of €152 billion by 2029, committing to 5% of its Gross Domestic Product (GDP) to defence and intending to become the strongest European armed forces by 2039 (Franke and Hubert 2025, 106; Höller 2026). Yet conventional forces cannot substitute for extended nuclear deterrence and the timeline problem makes this increasingly clear.

Germany currently has approximately 185,000 active-duty personnel (Central Intelligence Agency 2023) and 34,000 reservists (Franke and Hubert 2025, 108). NATO’s force requirement of 460,000 active and reserve soldiers suggests a gap of over 240,000 German defence personnel that voluntary recruitment cannot realistically fill (Frick and Haese 2025). Procurement contracts authorised in 2025 carry delivery timelines extending to 2030 (Großwald 2025). Rheinmetall's ammunition production targets 350,000 rounds annually, yet the war in Ukraine has demonstrated that modern peer conflict consumes munitions at rates that dwarf such capacity (Eckert 2025). The constitutional authority and fiscal capacity for conventional armament exist, but the time does not.

Conventional forces provide no answer to nuclear coercion. Against a nuclear-armed Russia possessing over 5,000 warheads, conventional military power cannot provide ultimate security (International Campaign to Abolish Nuclear Weapons 2026). Historical experience confirms that non-nuclear states facing nuclear-armed adversaries exist in a vulnerability that tanks and fighter jets cannot fix. If the U.S. nuclear umbrella disappears, non-nuclear NATO members will face an existential deterrence gap that no amount of conventional investment can close. Should the U.S. leave NATO, the U.S. B61 bombs currently stored across NATO Host Nations (Germany, Belgium Italy, the Netherlands and Turkey) under NATO's nuclear sharing arrangement would likely depart with U.S. forces (Centre for Arms Control and Non-Proliferation 2021), severing the alliance’s only direct connection to nuclear deterrence.

Europe's Latent Capability and Its Limits

Europe is not starting from zero. France maintains a fully sovereign deterrent (the Force de Frappe) consisting of roughly 290 nuclear warheads (Kristensen et al. 2023), four Le Triomphant-class submarines carrying M51 ballistic missiles and Rafale B fighters carrying air-launched cruise missiles (Charpentreau 2025; Maitre 2025, 3). France spends approximately €6.6 billion annually on nuclear deterrence, which represents around 13–14% of its total defence budget (Olech 2025). The UK’s Trident program, while technically integrated with the U.S. through leased missiles and shared warhead designs, maintains operational sovereignty through four Vanguard-class submarines and approximately 225 warheads (Mills 2025).

In combination, a coordinated French and British deterrent already totals roughly 515 warheads, which is a figure comparable to China's estimated 600 nuclear weapons (International Campaign to Abolish Nuclear Weapons 2026) and sufficient to survive a first strike and inflict catastrophic retaliation (Freedman 2025, 15). Minimum deterrence theory argues that a small, survivable force capable of inflicting unacceptable damage on key targets is sufficient to deter a rational adversary, with large arsenals offering diminishing strategic returns beyond a certain threshold (Forsyth et al. 2010). This theory applies to a potential French-British deterrent. Europe does not need to match Russia warhead-for-warhead. Instead, it needs a credible, survivable second-strike capability which already exists in a developing form.

The problem is doctrinal. Neither France nor the UK developed their arsenals to protect other states. De Gaulle's founding vision in 1967 explicitly sought to ensure France would not be “drawn into any quarrel that was not her own” (Tertrais 2020, 8). The UK similarly pursued nuclear status to secure "a seat at the top table" of diplomacy (Freedman 2025, 12). While both nations now acknowledge a "European dimension" to their vital interests (Macron 2025, as cited in Charpentreau 2025), final launch authority remains strictly with their heads of state. This structure matters because extended deterrence depends on an adversary believing that a nuclear power will risk its own destruction to defend another state (Schelling 1966). The strategic ambiguity between political rhetoric and operational doctrine is precisely where European extended deterrence remains most fragile. Essentially, the question is whether or not Paris or London would be willing to launch on behalf of Warsaw or Tallinn.

The Policy Argument: From Declaratory Openness to Institutional Commitment

President Macron’s recent willingness to discuss the European dimension of France's deterrent is politically significant, however it is not strategically sufficient. Credible extended deterrence requires the kind of institutional architecture that NATO's nuclear planning structures were built to provide. Europe currently has neither the consultative mechanisms nor the joint planning frameworks necessary to make a French or British deterrent credibly extend to cover Germany, Poland or the Baltic states. Multiple decision-making centres are, in theory, a strategic asset. An adversary like Russia would need to calculate whether a strike against one European state might trigger independent responses from two or three nuclear powers simultaneously (Davis 2015, 8). That complexity only functions as deterrence if the underlying commitments are credible and the command arrangements are coherent. As of right now they are neither.

The political preconditions for progress do exist. For example, German public opinion shows a rare convergence where 64% of Germans support a European nuclear umbrella independent of the U.S., while an equal percentage reject an independent German bomb (DEFCROS News 2025). Germans distinguish sharply between collective European deterrence and sovereign German nuclear capability and that distinction creates the political space for a coordinated French-British umbrella in a way that German armament alone could not. Germany’s Chancellor Merz has actively supported exploring nuclear sharing with France and the UK (Jacoby 2026). The political demand for a European solution is there but the institutional architecture to deliver it does not yet exist.

Recommendations

First, France and the UK should establish a formal European Nuclear Consultative Group (ENCG), which is already being discussed. Modelled loosely on NATO's existing Nuclear Planning Group (NATO 2026), but operating independently of U.S. authorization, this body should begin developing shared targeting doctrine, crisis communication guidelines and force posture planning relevant to Europe. Neither Paris nor London is being asked to surrender sovereign launch authority, they are asked only to create the institutional infrastructure that makes extended deterrence credible rather than rhetorical.

Second, Germany should be brought into nuclear planning discussions as a formal non-nuclear participant. Germany already contributes dual-capable F-35 aircraft and trained pilots to NATO's nuclear sharing arrangement (Nuclear Sharing 2023). Those assets are directly relevant to any European deterrent architecture and should not exit the conversation simply because the U.S. weapons they were designed to carry may be withdrawn. Germany's participation in planning, without possession, represents a model that is legally viable under existing treaty frameworks and politically defensible domestically.

Third, the ENCG should commission a concrete assessment of what minimum deterrence coverage of NATO's eastern flank requires. The deterrence problem facing Poland, Estonia or Latvia is different from the one facing France or the UK. A credible European umbrella requires an honest analysis of what deployment postures, communication arrangements and policies would be necessary to extend deterrence eastward with sufficient credibility. 

Fourth, NATO should begin formally adapting its nuclear planning structures for a reduced or conditional U.S. role. The alliance's current decision-making architecture was built for a U.S.-led model. If European states are increasingly bearing the primary burden of both conventional and nuclear deterrence, the institutional structures through which those commitments are made need to reflect that reality. A NATO that cannot adapt its governance to a post-U.S.-leadership scenario is a NATO that may fragment precisely when coherence matters most.

Conclusion

The U.S. nuclear umbrella was never unconditional. It was a political commitment maintained through costly investments, forward deployments and decades of consistent global crisis management. That commitment is now being questioned at the highest levels of U.S. leadership and Europe does not have the luxury of deliberating indefinitely. France and the UK possess the material basis for a credible European nuclear deterrent. What they lack and what must urgently be constructed is the institutional architecture to make that deterrent extend beyond their own borders. The window is narrowing and the cost of inaction is strategic exposure.

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