What is new about Macron’s invitation?

Macron for the first time explicitly indicated that France may declare it is prepared to use nuclear weapons in defence of its allies. Such suggestions have been made by French leaders before, but they have been ambiguous. During the Cold War, they referred to a potential strike on Warsaw Pact troops in case they invaded the neighbouring West Germany and the Benelux countries, mainly because it would threaten France itself. After the Cold War, successive French presidents pointed out that European integration increased the overlap of France’s vital interests, which are to be protected by nuclear deterrence, and its partners. Macron has emphasised since 2020 that these interests have a “European dimension” and has offered dialogue on the role of France’s nuclear forces in collective security.

Several factors are influencing France’s stronger rhetoric. In addition to the threat posed by Russia, which repeatedly resorts to nuclear intimidation, they include growing concerns about the reliability of the U.S. as an ally and its commitment to NATO. This is due, among other things, to the Trump administration’s desire to reset the relationship with an aggressive Russia, pressure on Ukraine regarding a peace agreement, and suggestions that the U.S. will cut its military presence in Europe. In addition, allies are more interested in the French offer. Marcon referred to the words of the likely future German Chancellor Friedrich Merz, who called for a discussion on U.S.-independent nuclear deterrence in Europe.

What role does the French nuclear arsenal play in NATO today?

Since 1974, NATO countries have recognised that French (and British) nuclear forces strengthen the security of the entire Alliance, although the U.S. deterrent  has the most important role. The NATO 2022 strategic concept specifies that these forces complicate the calculations of potential adversaries, as they must take into account the possibility of a nuclear response coming not only from the U.S. but also from the two other NATO nuclear powers.

The complementary role of the French and British nuclear forces stems from their relatively small size and therefore lesser ability to be used in defence of their allies. The U.S. has almost 4,000 nuclear warheads (Russia has an estimated few hundred more), while France has around 290 and the UK up to 260. In practice, most of the French and British arsenals are intended for massive use in retaliation for a substantial attack on these countries. Such a response would not be credible in reaction to an attack against an ally, as Russia could respond with a massive strike against France (or the UK). Furthermore, the concepts discussed in Russia for the use of nuclear weapons in Europe focus on limited strikes (among other things, in terms of the numbers of warheads and target selection). A selective Western response would be more credible, and France has larger capabilities in this area than the UK. Both countries have nuclear-armed ballistic missiles that can be launched from submarines and are primarily weapons of mass retaliation, while France also has shorter-range air-launched cruise missiles.

Unlike the U.S. and the UK, France has not declared its readiness to use nuclear weapons in defence of its allies and does not participate in joint planning of such operations in NATO. This is traditionally intended  to demonstrate French independence, especially from the U.S.

How could France increase the credibility of nuclear protection for its allies?

An important step would be for France to declare that it can use nuclear weapons to defend its allies. Macron has not yet made such a declaration, but in his speech on 5 March he indicated that it is likely. Contrary to the concerns that have been present in French discussions for years, this would not deprive France of its decision-making power in this area, nor would it deprive it of room for manoeuvre in a crisis. On the other hand, it would send a clearer signal to Russia that a nuclear response is a real option. It is also advisable to change the French nuclear doctrine, which currently assumes the possibility of only one limited nuclear strike, while Russia allows for gradual, repeated attacks. The French doctrine was formulated during the Cold War, assuming that such a single limited nuclear strike would be a “final warning” to invading forces approaching France, and that if they continued to advance, a massive retaliation would be launched against the USSR.

France is apparently not currently prepared to deploy nuclear weapons on allied territory. This would be a revolutionary change in the French approach to deterrence. The small size of France’s nuclear forces would also be a limiting actor. Such a move would become more likely if transatlantic relations were to erode further, especially if the U.S. were to leave NATO or withdraw its nuclear weapons from Europe. There are also no signs that France is considering increasing the size of its nuclear force. In the near future, the most realistic options for France using its nuclear forces to signal its determination to defend its allies are the more frequent presence of aircraft equipped to carry nuclear weapons on their territory, as well as the participation of allied conventional forces in French nuclear exercises.

Could France replace the U.S. nuclear deterrence in Europe?

Macron has not declared the desire to replace the American extended nuclear deterrence, but has indicated the need to prepare for a scenario in which the U.S. forces leave Europe. From a military point of view, France, even in cooperation with the UK, would not be as militarily credible in deterring Russia’s nuclear use against allies as the U.S. The French capacity to signal and respond to the selective use of nuclear weapons could be increased in the longer term through investment in the expansion of nuclear forces. However, it is unrealistic to expect that France and the UK will be able to destroy the majority of Russia’s nuclear arsenal in the foreseeable future. Russian military leaders, experts, and politicians have repeatedly expressed their concerns about the possibility of such a large-scale strike by the U.S. using nuclear and non-nuclear weapons. These concerns may—although do not have to—influence Russia’s calculations regarding a possible aggression against NATO.

However, extending the French deterrent to its allies would create escalation risks for Russia if it were to use nuclear weapons, even if not as high as in a confrontation with the U.S. This seems to be confirmed by the criticism by the Russian authorities of Macron’s speech, including Foreign Minister Sergei Lavrov’s describing his remarks on nuclear deterrence as a “threat” to Russia. Increasing the role of French (and British) nuclear forces would also be the fastest way to try to at least partially fill the gap in nuclear deterrence in the event of a U.S. withdrawal from Europe.