Why UK and France are joining nuclear forces—and what it means for Europe

The agreement comes at a time when Trump’s White House has publicly cast doubt on America’s commitment to NATO’s collective defence guarantee

The UK and France have pledged, for the first time in history, to coordinate the use of their nuclear weapons, saying they would jointly respond to any extreme threat to Europe. The move marks a significant shift in European defence policy as fears grow over Russia’s military ambitions and doubts linger about America’s future commitment under US President Donald Trump, the Financial Times reported.

The agreement, announced during French President Emmanuel Macron’s state visit to Britain, underscores the growing strategic alignment between Europe’s two nuclear-armed nations. While both the UK and France maintain independent arsenals, the new arrangement means their deterrents will now be capable of coordinated action to defend the continent.

“There is no extreme threat to Europe that would not prompt a response by both nations,” the UK government said in a statement. “Any adversary threatening the vital interests of Britain or France could be confronted by the strength of the nuclear forces of both nations.”

Officials from the Élysée Palace described the move as a message “to our allies and our adversaries” — a signal of strengthened solidarity and shared responsibility in an increasingly unstable world.

The agreement comes at a time when Trump’s White House has publicly cast doubt on America’s commitment to NATO’s collective defence guarantee. That uncertainty has led European capitals — notably Berlin — to quietly explore alternatives to the US-led nuclear umbrella.

France, which has historically rejected NATO’s nuclear-sharing agreement, has always maintained complete control over its homegrown nuclear force, which includes both submarine-launched and air-launched weapons. The UK’s deterrent, though reliant on US-supplied Trident missiles, is also operated independently via submarines and may soon expand with air-launched options using American F-35A jets.

While the UK and France had previously signalled mutual support — notably in the 1995 Chequers declaration — this latest commitment represents a doctrinal shift. Analysts say it may pave the way for operational cooperation such as coordinating submarine patrols to maintain round-the-clock deterrence.

“It is a quite powerful statement of the Franco-British commitment to European security,” said Camille Grand, a former NATO official now with the European Council on Foreign Relations. “Given the relatively small size of their arsenals, coordination makes strategic sense.”

Lawrence Freedman, emeritus professor at King’s College London, noted that France has long avoided publicly acknowledging coordination with any partner. “That in itself is quite an important development,” he said.

Beyond nuclear matters, the leaders also unveiled the “Lancaster House 2.0 declaration,” an updated version of the original 2010 Franco-British defence pact. The new agreement includes joint projects to develop long-range missiles to replace the Storm Shadow/Scalp, new air-to-air missiles, microwave weapons, drone jammers, and AI-powered coordinated strike systems.

The joint nuclear doctrine and broader military cooperation represent a historic deepening of Europe’s defence capability — one that aims to plug the gap left by a retreating America and to send a clear message to Moscow: Europe is arming together.