French President Emmanuel Macron has called on European leaders to discuss whether - and how - France's nuclear arsenal can serve as a deterrent against future Russian aggression.
However, allies may not like the restrictions Macron could place on strike force, or French nuclear power.
The idea of expanding France's "nuclear umbrella" to protect other European countries gained momentum after Donald Trump questioned the role of NATO and threatened to abandon the position the US has held as the ultimate guarantor of Europe's security since World War II.
“No European country has ever asked for something like this before, because no one wanted to question US support,” said Hubert Vedrin, a former French foreign minister who worked on the country’s nuclear doctrine.
"The debate that is now opening up is taking us into uncharted waters and it will be very difficult to find a solution."
In addition to the vast arsenal located in the United States, the US nuclear shield also includes more than 100 gravity bombs deployed in Europe. These bombs are under US control, but under NATO's "nuclear sharing" agreement, they are intended for use on fighter jets flown by Belgium, Germany, Greece, Italy, the Netherlands and Turkey.
Although no one in Europe wants the US to withdraw from the nuclear protection framework, the fear of such a scenario is so great that the leaders of two pro-American countries, Germany and Poland, recently stated that preparations for this possibility must begin.
Friedrich Merz, the future German chancellor, requested talks on whether “the nuclear protection of Great Britain and France could be extended to us.” Polish Prime Minister Donald Tusk welcomed the idea and even said that Poland should consider acquiring its own nuclear weapons. Lithuania and Latvia have also expressed interest in the French offer.
In response to these initiatives, Macron offered to “open a strategic debate” with interested European countries, lasting several months, to determine “whether new forms of cooperation can be developed.”
France has argued for decades that its “vital interests” – the factors that determine the use of nuclear weapons – have a “European dimension.” However, Paris has never precisely defined this term, so as to give the president as broad an option as possible and to keep the adversary in limbo – the key to any nuclear deterrent.
The talks, led by Emmanuel Macron, are expected to include the United Kingdom, the only other nuclear power in the region. Given that Britain's nuclear arsenal is already intended to protect Europe through NATO, Macron will have to show what he is prepared to offer.
Even if France does want to extend nuclear protection to Europe, experts say its arsenal of about 300 warheads - a paltry number compared to the US's 5.000 - is too small to protect the entire continent. Russia has 5.580 warheads and recently moved some of them to Belarus.
Paris also lacks tactical nuclear weapons — less destructive, short-range warheads designed for use on the battlefield — and, compared to the US and Russia, has fewer options for gradual escalation. In the event of a serious threat, France would carry out a “warning nuclear strike” on an adversary before striking key targets, such as major cities.
The British submarine-based nuclear deterrent system uses up to 260 British warheads, which are launched by American Trident missiles, and is assigned to NATO. In contrast, France, which uses nuclear weapons designed and manufactured exclusively in France, does not participate in NATO's Nuclear Planning Group (NPG), the forum that coordinates the alliance's nuclear policy.
The simplest and quickest way for France to strengthen the European nuclear shield would be to join the NPG and dedicate its nuclear capabilities to collective defense, said Marion Mesmer, an international security expert at Britain's Chatham House.
This would align French and British nuclear doctrine, integrate planning and facilitate crisis training, she added. For Russia, it would be a clear signal of France's commitment to Europe, but also proof that NATO - even as a predominantly European alliance - would remain strong even if the US withdrew.
But this would reverse France's long-standing tradition of nuclear independence, dating back to the time of General Charles de Gaulle, who believed that American security promises could not be fully accepted. Macron has repeatedly stressed that the French president would always have the final say on the use of nuclear weapons - the same rule applies to Britain and the US within NATO.
The joint nuclear capabilities of Britain and France would at least make Moscow think twice before possibly attacking, a senior Western official said.
However, he added that “what really influences Russia's decisions is the scale of the American nuclear deterrent.” If Europe wanted to reach that level and acquire an additional 1.000 warheads, it would have to spend 6-7% of GDP for at least a decade.
Without such a major expansion, France still has some options, former officials and experts said. Chief among them would be to more clearly define its nuclear doctrine, or explain how it could come to the aid of European allies, even if that might one day limit the president's discretion.
Camille Grand, a former senior NATO official who now works at the European Council on Foreign Relations, said France needs to become more precise in its positions.
"If every question our allies ask is answered simply: 'Trust us, the French president will act when he deems it necessary,' then we are not creating something that inspires much confidence in our allies," Gran said.
There are precedents that could serve as a model for expanded nuclear deterrence. In 1995, Britain and France stated in the so-called Chequers Declaration that they could not conceive of a situation in which “the vital interests of one of our two states could be threatened without the vital interests of the other being simultaneously threatened.”
One possible scenario now could be a similar statement in cooperation with other allied countries, or even linking it to the European Union's mutual defense clause.
An additional step could be to increase joint military exercises and training to send a signal to Russia that European allies are firmly connected. In 2022, an Italian refueling aircraft participated in a French nuclear military exercise for the first time.
In early March 2024, France hosted NATO ambassadors at the Istres air base, in the south of the country, to present their nuclear deterrent capabilities in more detail.
Bruno Tertre, a leading expert on nuclear deterrence, recently wrote in Le Monde that France could send a “strong operational signal” by temporarily deploying Rafale fighters, but without nuclear warheads, to the bases of its “most concerned partners, such as Poland.”
Paris could also request participation in NATO's Nuclear Planning Group (NPG) as an observer.
However, any significant step would imply a fundamental paradigm shift in French nuclear strategy, but also in that of its European allies. Such a shift would be neither necessary nor justified unless the US were to truly withdraw completely from protecting Europe.
Gran, a former senior NATO official, warned that it would be a mistake for Europe to try to replicate the US nuclear umbrella or create a “poor version” of that system. “We need to collectively come up with something different,” he urged.
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