On 10 July 2025, during French President Emmanuel Macron’s state visit to the United Kingdom, Paris and London signed the Northwood Declaration, a joint statement of intent to coordinate their nuclear deterrents in the face of mounting global and regional threats. The agreement affirms that an “extreme threat to Europe” would be regarded as a matter of “joint vital interest,” and signals a new phase in strategic cooperation between Europe’s only two nuclear-armed powers. This initiative forms part of the broader Lancaster House 2.0 Declaration, a comprehensive UK-France defence modernisation framework that includes deeper cooperation across cyber, artificial intelligence, missiles, and conventional military domains.
What is the Northwood Declaration?
While France and the UK have cooperated on nuclear matters before, through joint simulations, scientific collaboration, and military dialogues, the Northwood Declaration is the first public commitment to nuclear coordination at the doctrinal level.
The declaration comes amid increasing geopolitical instability: Russia’s continued aggression in Eastern Europe; ongoing uncertainty around the future of NATO; and growing concern across Europe regarding the reliability of U.S. security guarantees. While stopping short of any treaty-based integration of nuclear forces, the Northwood Declaration lays the groundwork for shared doctrine, strategic coordination, and operational alignment between two independent nuclear arsenals. This includes deeper exchanges on deterrence signalling and escalation thresholds for nuclear use, areas that have historically remained closely guarded. The aim is to ensure that in a future crisis, Franco-British deterrence can function in a more coherent and mutually reinforcing manner, even without a unified command.
The announcement was made from the UK’s Permanent Joint Headquarters in Northwood, lending the declaration its name. It is the most consequential nuclear understanding between the two countries since the 1995 Chequers Declaration. In the 1995 Chequers Declaration, France and the UK formally acknowledged the interconnection of their vital interests, reinforcing a shared strategic outlook within Europe’s nuclear landscape
At the heart of the Northwood Declaration is the shared understanding that an “extreme threat to Europe” would trigger a joint response from both nations. The precise definition of what qualifies as such a threat remains open, but analysts interpret this as a deliberate message: France and the UK are prepared to bring their nuclear postures into closer alignment, especially in situations involving Russian hostility, coercion, or threats to Europe’s security framework.
To begin implementing this coordination, the two countries have set up a Nuclear Steering Group, jointly led by officials from the Élysée and the UK Cabinet Office. This body will meet regularly to exchange views on nuclear doctrine, preparedness, and force posture.
Why is this agreement significant?
The move is widely seen as a response to the deteriorating European security environment. Since Russia’s full-scale invasion of Ukraine in 2022, European countries have increasingly sought to bolster their collective defence while simultaneously preparing for a scenario in which U.S. security guarantees might become less reliable, particularly under a second Trump administration.
French officials have long argued that Europe should take more responsibility for its own security, including through greater nuclear coordination. The UK, traditionally closer to the U.S. and NATO structures, appears more open now to aligning with France amid shifting strategic realities.
The agreement also emerges in the context of growing cyber and hybrid threats. Notably, under Lancaster House 2.0, the UK has pledged to support France’s Cyber Academy, while France will contribute to the development of the UK’s new Cyber and Electromagnetic Activities (CEMA) Command. These moves signal a wider trust-based convergence on highly sensitive capabilities.
The declaration also follows recent reports that Russia has deployed short-range nuclear-capable systems in Kaliningrad and Belarus, reinforcing concerns about a possible nuclear component in future Russian military strategies.
What is the current state of French and UK nuclear forces?
France and the United Kingdom are Europe’s only nuclear-armed states and permanent members of the UN Security Council. Both maintain relatively small but technologically advanced arsenals. The UK previously operated a mix of air- and sea-based delivery systems, relying on aircraft such as the Avro Vulcan bombers armed with WE.177 gravity bombs, before retiring its air-based capability in 1998. Today, it relies exclusively on a sea-based deterrent through its fleet of four Vanguard-class submarines, soon to be replaced by the Dreadnought-class, armed with Trident ballistic missiles.
France deploys its nuclear weapons through two main delivery systems: a fleet of four Triomphant-class submarines at sea, and a set of nuclear-capable Rafale fighter jets for air-based delivery. Current estimates suggest that the UK holds about 225 nuclear warheads, while France is believed to maintain around 290.
The UK and France built their nuclear forces on diverging political foundations that continue to shape their strategic outlooks today. The UK built its nuclear capability with substantial support from the U.S., joining the nuclear club in the 1950s and integrating its posture within NATO’s extended deterrence framework. France, in contrast, opted for an entirely independent path. Under the leadership of Charles de Gaulle, it constructed its own nuclear force, known as the force de frappe, which reflected a belief that genuine sovereignty required self-reliance in matters of national defence. That distinction still shapes how the two countries think about nuclear strategy today.
Neither state hosts American nuclear weapons on its territory, and both maintain full operational control over their respective arsenals. The UK’s missiles, although produced in the U.S., remain under British command. France, consistent with its long-standing emphasis on autonomy, manufactures all components of its nuclear deterrent domestically.
Is this a step toward a collective European nuclear force?
British and French officials have made it categorically clear that the Northwood Declaration is intended to complement, not replace, NATO. The idea of a European nuclear deterrent, commonly referred to as a “Eurodeterrent,” has existed in policy circles for years but remains politically controversial. France has traditionally guarded its force de frappe as an expression of national sovereignty, while the UK’s nuclear forces rely heavily on U.S. logistical and technical support through the Trident program.
Still, by formally coordinating nuclear doctrines, threat perceptions, and response scenarios, the new declaration pushes both countries closer to a shared strategic mindset. It can be a quiet but unmistakable foundation for future European deterrence planning.
