A New Entente Cordiale in an Age of Uncertainty? The Northwood Declaration in Franco-British Nuclear Cooperation
By Guglielmo Giunta, University of Roma Tre
Over the past two decades, nuclear weapons have returned to the centre of European security as a result of consistent and compounding changes to global geopolitics. For most of the post-Cold War era, weapons of mass destruction appeared to have lost salience as the disappearance of bipolar confrontation, the expansion of cooperative security frameworks, and the consolidation of arms control regimes fostered the belief that large-scale interstate conflict in Europe was a phenomenon of the past. However, Russia’s full-scale invasion of Ukraine in 2022, the collapse of arms control frameworks and agreements, and growing uncertainty surrounding the durability of security guarantees from the United States (US) have altered these assumptions, forcing a reassessment of the role of nuclear deterrence in Europe. Nuclear weapons have now regained centrality in European security as instruments of coercion, signalling, and strategic reassurance.
These dynamics have rekindled a nuclear debate in a number of European states, including the United Kingdom (UK) and France – Western Europe’s only two nuclear powers – who came together in July 2025 to sign the Northwood Declaration. This Declaration represents a significant political step for European nuclear security as, for the first time, both French and British governments publicly recognize that their independent nuclear forces must be thought of as a nuclear tandem in upholding the security of Europe. The political significance of this Declaration is much greater than its technical content and raises the following questions: does Northwood Declaration represent a strategic turning point in Franco-British nuclear cooperation in the context of perceived US disengagement from Europe and renewed Russian assertiveness? Can this renewed commitment to cooperation bridge the UK and France’s historically distinct strategic traditions regarding nuclear weapons?
Historical Background: A Persistent Strategic Asymmetry
Nuclear relations between the UK and France have always been shaped by a triangulated great power partnership that necessarily involved the US. The UK’s nuclear program was deeply embedded in Anglo-American cooperation from the Second World War onward. The 1958 Mutual Defence Agreement institutionalized this relationship, giving the UK access to American technology, materials, and missile systems. The credibility of the British deterrent therefore rested not only on national capability but also on continued US support.
France followed the opposite path. Excluded from early nuclear cooperation and sceptical of extended deterrence, Paris developed its force de frappe as an explicit sovereign instrument. The French nuclear doctrine emphasized national decision-making, freedom of action, and the political symbolism of independence. Deterrence was not merely military protection; it was a guarantee of strategic autonomy.
These divergent trajectories repeatedly complicated bilateral cooperation between France and the UK. During the Cold War, the UK could not easily share nuclear information without American approval while France refused to subordinate its deterrent to any external framework, including NATO. Even moments of diplomatic convergence produced mostly rhetorical statements rather than operational coordination.
After 1991, the issue temporarily lost urgency. Arms control agreements, reduced geopolitical tensions, and the shift toward crisis management operations moved nuclear questions into the background. Franco-British defence cooperation deepened through initiatives such as the Saint-Malo Declaration (1998) and later the Lancaster House Treaties (2010), though these agreements focused largely on conventional capabilities and technical collaboration. Nuclear policy remained politically sensitive and largely separate from coordinated strategic planning.
The Return of Nuclear Politics in Europe
The strategic environment, already undergoing gradual change, shifted dramatically after 2014. Russia’s annexation of Crimea and the outbreak of armed conflict in Donbas marked the return of conventional warfare in Europe. More importantly, Moscow accompanied its actions with nuclear-related deterrence signalling intended to discourage Western military intervention, including readiness messaging, strategic exercises, and official statements referencing nuclear doctrine. While these signals remained largely indirect at the time, they reintroduced the nuclear dimension into European security. Since 2022, Russian rhetoric has become far more overt, with explicit nuclear threats entering regular political communication.
At the same time, the institutional foundations of nuclear stability weakened. The US withdrawal from the JCPOA (8 May 2018), the collapse of the INF Treaty (2 August 2019), the New START expiration (5 February 2026), and the broader erosion of arms control norms removed many stabilizing constraints inherited from the Cold War. These developments coincided with a gradual reorientation of US strategy toward the Indo-Pacific. Beginning with the Obama administration’s “pivot” to Asia in 2011, American security policy increasingly prioritized China as its primary long-term strategic competitor. Although Washington did not disengage from NATO, successive administrations placed growing emphasis on burden-sharing and regional prioritization, encouraging European Allies to assume greater responsibility for their own security. This trend became particularly explicit during the two Trump administrations, whose strategic discourse framed alliances less as unconditional commitments and more as partnerships requiring reciprocal contribution from its partners.
For European states, the combination of Russian coercion and America’s shifting security priorities created a dilemma. NATO’s deterrence remained credible, yet its perceived unconditionality weakened. European security increasingly depended on whether Europeans could carry a larger share of the burden of deterrence in a crisis directly affecting the continent, rather than relying exclusively on automatic US escalation. In this context, nuclear discourse has regained political salience for European NATO Allies. The issue is no longer deterrence itself, but who will be responsible for making deterrence credible in a crisis directly affecting Europe.
The Northwood Declaration
The 2025 Northwood Declaration must be understood in the context of this shifting dynamic. This Declaration does not create a joint Franco-British nuclear force; however, its significance lies in its political message that British and French nuclear deterrents can be coordinated and jointly considered in the management of European security.
The creation of the UK-France Nuclear Steering Group through this Declaration introduces a permanent mechanism for political consultation across nuclear policy, capabilities, and operations. However, national decision-making authority remains unaffected and both France and the UK retain explicit sovereignty over their nuclear arsenals. This step represents an important qualitative change. Previous cooperation – particularly under the Lancaster House Treaties – focused on technical collaboration, such as stockpile stewardship and research facilities. Nuclear policy itself remained politically insulated. Northwood, by contrast, brings nuclear cooperation into the political sphere. For the first time, both British and French governments openly accept that their nuclear forces cannot be treated as separate national assets in a risky European security environment.
The Declaration also restates the long-standing formulation that the vital interests of one country cannot be threatened without affecting those of the other, a wording that originates from the 1995 Franco-British Joint Declaration on Nuclear Policy. In the contemporary context, this relational language carries broader implications than in the 1990s, as it signals a shared willingness to extend nuclear deterrence across Europe.
Reconciling Atlanticism and Autonomy
Does this development have broader implications for transatlantic security? Does it reconcile the United Kingdom’s US-integrated deterrent posture with France’s doctrine of independent nuclear decision-making? The answer is both yes and no. The UK has not abandoned its reliance on the US. Its submarine-based deterrent still depends on American missile systems and technical knowhow. Participation in NATO nuclear planning and the acquisition of dual-capable aircraft further reinforce transatlantic integration. France, on the other hand, has not diluted its doctrine of independence. It remains outside NATO’s nuclear planning structures and continues to emphasize sovereign decision-making, as President Macron reaffirmed in his speech in March 2026.
The Northwood Declaration therefore does not produce doctrinal convergence. Instead, it provides functional political alignment. Both states retain their respective strategic identities while deepening political cooperation in response to a shared perception of risk. The significance of this shift lies precisely in its pragmatism. Rather than forcing institutional integration – which would be politically unacceptable to both sides – the declaration creates a cooperative interface. The UK derives credibility from its integration with NATO and its nuclear relationship with the US, whereas France derives that same credibility from autonomous national decision-making. The political coordination provided by the Northwood Declaration therefore does not merge the two deterrents but instead creates parallel centres of nuclear decision-making aligned in a common strategic posture, complicating an adversary’s assessment of escalation.
In effect, coordination substitutes for doctrinal reconciliation. The Declaration does not remove the structural tension between NATO dependence and strategic autonomy; it manages this tension by transforming it into coordinated political signalling.
Implications for European Deterrence
The Northwood Declaration importantly does not create a European nuclear deterrent. No extended guarantee is offered, no shared command established. Hence, US extended deterrence and NATO remain central for many European states. However, the Declaration does still alter the strategic landscape in Europe.
By coordinating their deterrents politically, the UK and France introduce a European layer of nuclear signalling within the transatlantic system. This European layer operates through identifiable mechanisms. For European NATO Allies, the public coordination of the two nuclear powers signals that deterrence credibility does not depend exclusively on immediate US escalation. For a potential adversary, the existence of two politically aligned but nationally independent nuclear decision-makers introduces uncertainty about escalation thresholds and responses. At the same time, the political burden of deterrence is no longer borne solely by Washington, as London and Paris visibly assume a larger role in strategic signalling and crisis management.
The result is best understood as a hedge. It is designed to supplement American guarantees rather than replace them. In a crisis, adversaries must consider not only NATO and the US, but also the combined political stance of Europe’s two nuclear powers. Over time, this may influence how deterrence is discussed within Europe. While not establishing a European nuclear force, the Northwood Declaration makes European nuclear responsibility a legitimate topic of policy rather than a theoretical debate.
The Northwood Declaration fits within a broader pattern in which nuclear deterrence is no longer confined to NATO’s internal mechanisms. In this sense, the Declaration may represent a catalyst for deeper dialogue and coordination between European nuclear and non-nuclear actors. An early indication of this dynamic emerged with the Kensington Treaty of 17 July 2025 through which the UK and the Federal Republic of Germany agreed to pursue deep exchanges on deterrence, nuclear issues and arms control, as well as a permanent dialogue on defence matters, while also envisaging intensified trilateral cooperation with France. Furthermore, a joint declaration of President Macron and Chancellor Merz on 2 March 2026 established a Franco-German nuclear steering group intended to serve as a bilateral framework for doctrinal dialogue and strategic coordination.
More recently, this broader trend has been further reinforced by the French President’s proposal of a doctrine of dissuasion avancée (advanced deterrence) which envisages deeper forms of political and strategic coordination between France and a group of willing European partners, including both nuclear and non-nuclear states. While stopping short of creating a European nuclear deterrent, the initiative seeks to institutionalize regular consultations and coordination on deterrence-related issues within a framework explicitly presented as complementary to NATO.
Limits and Constraints
Despite its significance, the Declaration faces important limitations. Structural asymmetries remain profound. The US still possesses nuclear capabilities vastly exceeding those of either France or the UK, but the relevant comparison is broader: Russia maintains the world’s largest arsenal and China is rapidly expanding its own stockpiles.
A further limitation concerns the autonomy of the British deterrent. Although the UK retains sovereign political control over its nuclear forces, it also remains deeply intertwined with the US through the Mutual Defence Agreement, the Trident System, and broader technological cooperation. This creates structural limits on how far the UK can engage in deeper nuclear cooperation with its European nuclear and non-nuclear partners and how far the British nuclear deterrent can be Europeanized. However, the novelty concerning the French doctrine of “advanced deterrence” could be seen as another step towards a more extended deterrence.
Divergent defence-industrial partnerships also complicate long-term convergence. France’s cooperation with Germany contrasts with Britain’s global partnerships such as the Global Combat Air Program. Regional priorities differ as well. The UK has increasingly oriented its security policy toward Northern Europe, most notably through its leadership of the Joint Expeditionary Force, a regional military framework bringing together Nordic and Baltic states for rapid crisis response and defence cooperation.
For these reasons, the Northwood Declaration should not be interpreted as the beginning of a fully integrated European nuclear structure. Its strength lies in political signalling rather than institutional transformation.
Conclusion
The Northwood Declaration represents a strategic turning point in Franco-British nuclear cooperation, but in a specific and carefully bounded sense. It does not dismantle the structural differences between British Atlanticism and French strategic autonomy. Rather, it lays the foundations for these two systems to operate together. By publicly acknowledging coordination and institutionalizing consultation, the Declaration moves cooperation from symbolic reassurance to structured political practice. The UK continues to rely on the US; France continues to emphasize autonomy. Yet both the UK and France recognize that, in this current era of intense geopolitical tension, the credibility of European deterrence increasingly depends on their political leadership. The Northwood Declaration is a strong signal that they are willing to assume that role together.