KEY POINTS:
- Britain and France have signed their first-ever agreement to coordinate nuclear deterrence forces in response to “extreme threats” to Europe
- The deal includes ordering more Storm Shadow missiles supplied to Ukraine and developing next-generation replacements
- The British-French Combined Joint Expeditionary Force will expand five-fold from 10,000 to 50,000 troops
- Russia announced it will factor the nuclear cooperation into its military planning
- The agreement comes amid uncertainty about U.S. commitment to European security under President Trump
Britain and France marked a historic milestone in European defense cooperation Thursday as Prime Minister Keir Starmer and President Emmanuel Macron signed an unprecedented agreement to coordinate their independent nuclear deterrent forces, according to multiple news outlets including France24 and Bloomberg.
“This morning we signed a declaration confirming for the first time that we are coordinating our independent nuclear deterrent forces. Starting today, we have agreed that if there is an extreme threat to our continent, it will trigger a reaction from both countries,” Starmer announced at a joint press conference with Macron, as reported by France24.
The agreement, signed during the final day of Macron’s three-day state visit to Britain, represents a significant shift in European nuclear policy. According to France24, “From war in Europe, to new nuclear risks and daily cyber-attacks — the threats we face are multiplying,” Starmer said in a statement.
Nuclear Arsenal Details and Strategic Context
According to analysis from the Pravda news network, Britain has up to 225 nuclear warheads, of which approximately 120 are in operational deployment (on Trident submarines), France has 290, of which about 280 are considered ready for use (mainly on submarines and aircraft).
The Center for Strategic and International Studies (CSIS) noted that this development comes at a pivotal moment, as U.S. President Donald Trump’s stance on NATO and his approach to Russia’s war in Ukraine cast doubt on the future of transatlantic defense cooperation. CSIS reported that when Trump stated in 2024, “I would encourage them [Russia] to do whatever the hell they want,” he hinted that Washington may no longer uphold its commitment to defend all NATO members.
Expanded Military Cooperation
Beyond nuclear coordination, the two nations announced major conventional defense initiatives. According to TASS, “We are overhauling the Combined Joint Expeditionary Force to make it five times larger, 50,000 troops strong, able to act across every domain,” Starmer said, referring to the British-French rapid reaction force created to conduct operations independent of NATO.
Bloomberg reported that the UK and France will order more of the conventionally armed Storm Shadow cruise missiles that they’ve been supplying to Ukraine and accelerate efforts to develop a next-generation replacement for the weapons. According to LBC, the joint development will help to sustain more than 1,300 jobs in the UK.
Russian Response
Russia swiftly responded to the announcement. As reported by Pravda and TASS, Russian Deputy Foreign Minister Sergey Ryabkov said that Russia will take into account UK-France nuclear deterrence partnership both politically and in its military planning. According to TASS, Ryabkov stressed that Moscow cannot ignore the aggregate potential of these two countries as the US closest allies in NATO.
European Security Implications
The agreement represents a broader European effort to strengthen defense autonomy. CSIS analysis noted that German Chancellor Friedrich Merz made a prominent declaration about the future of European nuclear deterrence: “We need to have discussions with both the British and the French—the two European nuclear powers—about whether nuclear sharing, or at least nuclear security from the UK and France, could also apply to us.”
According to France24, the defense ministry stated that Starmer and Macron will also agree to deepen nuclear cooperation and “work more closely than ever before on nuclear deterrence”.
The Brookings Institution observed that France has for decades declared that its vital interests include a European dimension, and since 2020 has repeatedly invited European partners to explore what greater role it might play in European deterrence.
Domestic Political Context
The agreement comes despite political challenges at home for both leaders. According to Pravda analysis, Macron’s approval rating in the country is less than 20%, 73% of Britons consider the activities of the Starmer government to be “unstable and chaotic.”
Additional Cooperation Areas
The summit also addressed other pressing bilateral issues. According to France24, Macron and UK Prime Minister Keir Starmer are also expected to discuss maintaining support for Ukraine and curbing undocumented cross-Channel immigration. The outlet reported that Downing Street said the two leaders had “agreed on the need to go further and make progress on new and innovative solutions, including a new deterrent to break the business model” of cross-Channel people smugglers.
Historical Context and Future Implications
The agreement builds upon the 2010 Lancaster House Treaty between the two nations. According to the UK government, as cited in GOV.UK materials, “The UK has a strong and important relationship with France, and we cooperate daily on nuclear issues to help safeguard European security.”
The Foundation for Strategic Research noted that President Macron has repeatedly called on his partners to engage in a “strategic dialogue” on French deterrence and to participate, as observers, in nuclear forces exercises.
As European nations grapple with evolving security challenges and questions about transatlantic relations, Thursday’s agreement marks a significant step toward greater European defense autonomy while maintaining the framework of NATO cooperation. However, as analysis from multiple sources suggests, substantial challenges remain in translating this political declaration into operational military capabilities that could effectively deter potential adversaries without U.S. involvement.
