Britain’s recent Strategic Defence Review recommends seeking a ‘closer relationship’ with France, ‘its European nuclear ally’. But Britain depends on US support for its nuclear capability and France, which is not part of the NATO Nuclear Planning Group, reserves its for national defence. In recent months, questions have been raised about the United States’ commitment to allies – how might Britain and France extend their ‘nuclear umbrella’?
Entente nuclear?
Britain and France have about 515 nuclear warheads between them – a fraction of Russia’s nuclear inventory, which is thought to number more than 5,000.
Source: ‘Estimated Global Nuclear Warhead Inventories’, Federation of American Scientists, 2025
Britain’s nuclear arsenal
Britain is part of the NATO Nuclear Planning Group and offers extended deterrence to Europe. Its nuclear deterrent, Trident, comprises four nuclear-armed Vanguard-class submarines. One of these submarines is deployed at all times in line with the UK’s Continuous At-Sea Deterrent policy. The UK maintains operational control over Trident, but the missiles are maintained and periodically refurbished in America. The submarines and their planned Dreadnought-class successor rely on American components.
Nuclear stockpile: 225 warheads
Delivery system: 4 nuclear-powered Vanguard-class submarines; each can carry 16 Trident II D5 missiles; each missile can carry 8 warheads.
France’s nuclear arsenal
Although it is a NATO member state, France reserves its nuclear weapons for national protection. Its nuclear deterrent can be delivered by aircraft and submarine. One submarine is deployed at all times. France’s nuclear enterprise is entirely domestically produced and maintained.
Nuclear stockpile: 290 warheads
Delivery systems: 4 nuclear-powered Triomphant-class submarines; each can carry 16 M51 missiles; each missile is capable of carrying 6 nuclear warheads. 50 land-based Rafale fighter-bomber aircraft (including 10 able to deploy from an aircraft carrier); each aircraft can carry a cruise missile with a single nuclear warhead.
Where are British, French and American nuclear forces in Europe?
Britain
Submarines: Faslane, Scotland ①.
France
Submarines: Ile Longue ②.
Aircraft: Saint-Dizier Air Base ③; Landivisiau Naval Aviation Base ④. Its single nuclear-capable aircraft carrier is based at Toulon ⑤.
United States
The US maintains and controls about 100 non-strategic nuclear weapons in five NATO member states across six airbases (below). They are stored in underground vaults in preparation for arming and deployment to fighter-bombers. The six airbases are thought to be: Kleine Brogel in Belgium ❶, Büchel in Germany ❷, Aviano and Ghedi in Italy ❸, ❹, Volkel in the Netherlands ❺, and Incirlik in Turkey ❻.
Extending Britain and France’s nuclear umbrella – the options
Option 1: The UK unilaterally builds up its domestic industrial capability for producing a submarine-launched ballistic missile (SLBM) to replace Trident and do away with the need for US technical support.
Assessment: Time-consuming and expensive.
Option 2: London and Paris agree to collaborate to allow the UK to source its SLBMs from France.
Assessment: Britain’s and France’s SLBM systems are similar. If they can be made compatible, Britain could benefit from France’s existing production line to procure missiles. Politics might hamper cooperation. French right-wing parties have expressed opposition to France sharing its nuclear deterrent.
Option 3: Britain and France receive financial compensation from European allies for providing nuclear capabilities to NATO.
Assessment: France has been reluctant to accept financial support for fear it might dilute its nuclear sovereignty. But a deal would bolster NATO’s nuclear deterrent.
Option 4: France joins the NATO Nuclear Planning Group, retaining sovereign nuclear decision-making, but integrating with NATO nuclear exercises.
Assessment: France’s NATO integration would boost the alliance’s deterrence posture. But France would be overturning decades of nuclear independence.
Options from recent Chatham House Expert Comments: ‘The UK’s nuclear deterrent relies on US support – but there are no other easy alternatives’ by Marion Messmer and Olivia O’Sullivan; ‘France should join NATO’s nuclear sharing arrangements to strengthen European deterrence’, by Messmer and Julia Cournoyer.
Due to the secrecy surrounding nuclear weapon programmes, several of the figures and geographic locations cited in this graphic are unconfirmed. Sources: Federation of American Scientists, CSIS Missile Threat, Centre for Arms Control and Non-Proliferation, Council on Geostrategy. Graphic illustrations: Alexander Ecob
Note: This story was revised on 14 July, 2025, with an updated chart indicating the estimated inventories of the nuclear-armed countries and the source of that data, the Federation of American Scientists