Are You MAD [Mutually Assured Destruction]? - Nuclear Sharing: Stakes and Limits for France

06/03/2026

Author

Resident Senior Fellow - Expert in Defense and National Security issues

As the geopolitical environment is becoming increasingly unstable (Vladimir Putin’s 2022 threat to use nuclear weapons in the event of European involvement in Ukraine, the expiration of the New START agreement in 2026-Russia having already suspended its participation in February 2023-American retrenchment from the Old Continent, etc.), voices in France and across Europe are calling for an extension of the French nuclear umbrella to Europe, that is, a form of sharing France’s nuclear deterrent. The debate regained momentum during the Munich Security Conference on February 14-15, when Chancellor Merz referred to "a European nuclear deterrence." But what fundamental issues would a possible "Europeanization" of France’s nuclear strike force raise? Would it affect the credibility of our national deterrence, even if the decision to use it remains strictly French? André Leblanc provides an overview of the key issues, in an interview structured around six questions.

1. What does it mean for France to be a nuclear-armed power?

French doctrine holds that the use of nuclear weapons is conceivable only in extreme circumstances of self-defense. It is intended to ensure the protection of the nation’s vital interests (with a deliberate ambiguity, but one could understand it to include territorial integrity, the protection of the population, and national sovereignty), including in the event of a conventional attack. Our doctrine clearly-and publicly-states that nuclear deterrence may apply to any type of aggression, nuclear or not.

By its very existence, French deterrence therefore sends a strategic signal to both nuclear-armed and non-nuclear-armed powers. To nuclear-armed states, France signals that it is prepared to resort to nuclear force-inflicting intolerable damage (even if this exposes it to atomic retaliation)-rather than endure an attack on its vital interests without responding. To non-nuclear-armed states, France signals that its vital interests must be regarded as beyond the reach of a conventional attack, since it would be prepared to respond with nuclear weapons. Nuclear weapons therefore imply a supreme dialectic of sovereignty.

2. At present, France already contributes to collective security within NATO: What are the implications for the French nuclear force?

France is a member of North Atlantic Treaty Organization and, as such, participates in NATO’s collective defense. However, French nuclear deterrence remains strictly national; it was built on the conviction that France must not depend on anyone for the ultimate safeguard of its vital interests.

Consequently, the alliance system established by France - within NATO (through Article 5) as well as through Article 42.7 of the Treaty on European Union - does not, as such, commit France’s nuclear capability. The system establishes France’s commitment to military solidarity, but France retains absolute discretion over the decision to resort to nuclear weapons.

Consequently, the alliance system established by France - within NATO (through Article 5) as well as through Article 42.7 of the Treaty on European Union - does not, as such, commit France’s nuclear capability. The system establishes France’s commitment to military solidarity, but France retains absolute discretion over the decision to resort to nuclear weapons.

We should pay heed nevertheless that when people speak of "nuclear sharing" or extending the French "nuclear umbrella," they are in fact drawing a parallel with the American arrangement within NATO. Yet this parallel is misleading (France is not to the European Union what the United States is to NATO) and can create confusion. The so-called American "nuclear umbrella" involves the stationing of U.S. weapons (B61 gravity bombs) in five NATO countries, four of which are European (Italy, Germany, the Netherlands, Belgium). These weapons remain under permanent U.S. control, and under NATO’s nuclear planning, in the event of a nuclear conflict and by U.S. decision, they could be made available to the host European countries-the decision would be American, while delivery would be carried out by the European countries concerned.

Once again, nothing comparable exists in the French case. France is a member of NATO and possesses nuclear weapons. However, France’s nuclear strike force is not subject to any third-party decision-making process.

3. Why might nuclear sharing be considered a risk to our deterrent force?

First of all, even if from the outset we rule out any sharing of the decision to use nuclear weapons, and limit ourselves to extending the scope covered by French deterrence, such an extension would in fact amount to sharing a French capability by broadening it to other countries-European countries, in this case.

When discussing the sharing of France’s nuclear deterrent, one argument often put forward is that it would be more credible for a French president to say he is ready to die for Kraków than for an American president to say he is ready to die for Hamburg. Logically, this argument is ineffective because it replaces a relative judgment (is A more credible than B?) with a categorical one (is A credible?). The only relevant question should be: Is a French nuclear deterrent covering non-French vital interests credible?

The granite foundation of deterrence is the result of years of incremental consolidation.

Since the French nuclear force has never been used, its credibility rests notably on the consistency of strategic signals communicated steadily and sparingly in the long term. In this respect, the granite foundation of deterrence is the result of years of incremental consolidation.

Endorsing nuclear sharing would therefore entail a significant risk: that of making the strength of our deterrence dependent on our ability to convince a nuclear-armed adversary that we would accept nuclear suicide if, for example, the vital interests of Poland were threatened. Should the adversary fail to believe this - which is a plausible hypothesis insofar as it would directly contradict the current doctrine of "extreme circumstances of legitimate self-defense" - the entire solidity of our credibility could be called into question.

4. To what extent would nuclear sharing constitute a strategic rupture?

Current debates surrounding the extension of French deterrence to European territory have been driven by several political impulses. President Emmanuel Macron, an advocate of European strategic autonomy, has on several occasions stated that the nation’s vital interests have a European dimension (notably in his speech at the École de Guerre on February 7 2020, in his televised address of March 5 2025, where he declared his intention to "open the strategic debate on protecting our European allies through our deterrence," and again at the Munich Security Conference on February 13 2026).

However, positing such an inclusion-or even equivalence-between French and European vital interests raises a number of difficulties of different kinds: strategic, ethical, diplomatic, EU-related, communal, and above all political.

From a strategic standpoint, the initial problem has been framed incorrectly. For France, the question is not what the best possible European nuclear deterrent might be (although this is a serious issue, recently examined by the European Nuclear Study Group in its report Mind the Deterrence Gap: Assessing Europe’s Nuclear Options. Interestingly, after reviewing all five possible options, the ENSG concludes that in the short term the American guarantee through NATO remains the most credible and feasible option for Europe). Rather, the question France must ask itself is: What is the best possible French deterrent? It is, of course, possible to argue that the best French deterrent is in fact a European one-but this point must be carefully demonstrated. It constitutes the first strategic problem to solved before examining other questions (doctrine, capabilities, deployments, etc.). Yet this central issue has largely been sidestepped in current debate.

From an ethical standpoint, extending French deterrence would not be without consequences, since French nuclear weapons are not tactical but strategic. By definition, their use would entail massive civilian casualties. A French decision causing civilian losses in the name of other European citizens would raise new questions in terms of accountability, responsibility, and legitimacy.

From a diplomatic standpoint, a French proposal to share its nuclear capabilities would generate a series of specific difficulties in light of the Treaty on the Non-Proliferation of Nuclear Weapons, which France ratified in 1992. The transfer of weapons, their components, or control-directly or indirectly-is prohibited under Article I (recipient European states would for their part violate Article II). Such an announcement-potentially interpreted as reigniting the nuclear arms race, and thus potentially violating Article VI-would be particularly ill-timed just two months before the opening of the 11th NPT Review Conference (to be held in New York from April 27 to May 22), especially in the period of uncertainty following the expiration of New START. In this specific context, a French proposal to "nuclearize" European defense could weaken the non-proliferation regime, risk isolating France, and make it the focal point of criticism-or even a scapegoat in the event of failure at the Review Conference.

From a strictly EU perspective, France may speak in the name of Europe, but there is currently no consensus on this issue within the EU. Several European countries-Austria, Ireland, and Malta-have signed and ratified the Treaty on the Prohibition of Nuclear Weapons. In Germany as well, although Chancellor Merz has indicated that he has initiated confidential discussions with France on European nuclear deterrence, there is reluctance on the matter, with some arguing that it sends a signal of distrust toward the Americans. This was emphasized, for example, by Boris Pistorius (SPD), Federal Minister of Defence, in Munich. One cannot exclude the possibility that a French initiative in this domain could trigger public divisions within the EU, thereby increasing European vulnerability by exposing disagreements on a core security issue.

Finally, nuclear sharing raises the fundamental political question of mandate. As the authority responsible for exercising nuclear deterrence, the President of the French Republic is the custodian-not the owner-of this sovereign national prerogative and therefore cannot alienate it. He holds the authority to commit French nuclear forces, but not to share it.

While strategy is meant to implement policy, here the reverse seems to be occurring: the strategic debate appears to be accelerating a policy that has not, as such, been formally articulated.

The idea of European nuclear sharing must therefore be treated first and foremost as a political issue. Strangely, while strategy is meant to implement policy, here the reverse seems to be occurring: the strategic debate appears to be accelerating a policy that has not, as such, been formally articulated.

5. In the event of nuclear sharing, what implementation options might be conceivable (trade-offs, governance)? What would this change?

The sharing of the final decision to employ nuclear weapons has been publicly ruled out. Under these conditions, what could theoretically be shared would include funding, geographical deployment, logistical support, operational planning, detection systems, etc. These different degrees of sharing would have two main types of consequences.

At the operational level, the credibility of deterrence would once again be called into question-even if there were a formal decoupling between the decision itself and the means that ultimately make it possible. For it is precisely this decoupling that would weaken the independence of the decision, and therefore its ultimate credibility. If the effectiveness of a nuclear strike depended, even partially, on assets financed, hosted, or technically enabled by third parties, the perception of autonomous control could be diluted in the eyes of a potential adversary.

If funding or doctrinal development no longer fell exclusively under French authority, or if the triggering of a nuclear strike depended on an alert provided by a third country, France’s sovereignty over its deterrent would be compromised.

At the political level, such degrees of sharing would be incompatible with the concept of nuclear sovereignty (since sovereignty, by definition, is absolute). If funding or doctrinal development no longer fell exclusively under French authority, or if the triggering of a nuclear strike depended on an alert provided by a third country, France’s sovereignty over its deterrent would be compromised.

6. What would be our interests in taking action?

From a French standpoint, a European sharing of the French nuclear deterrent presupposes that French vital interests and European vital interests coincide strictly. As long as this point has not been clearly established and validated, the question-as we have seen-remains problematic.

It is also significant that, during the Munich Security Conference, for the first time, the French President in his address called for going beyond the French dimension: "When I speak about Europe becoming a power, I don't speak about France or Germany becoming a power. I speak about Europe. So we have to think and act as Europeans, I would say, by design. And this is what we have to do now."

From this perspective, it may seem surprising to see "European sovereignty" appear as an objective in the last two National Strategic Reviews. The 2022 RNS is the first to refer to the "realization of European sovereignty." Traditionally, Defense White Papers or strategic reviews-whether French or foreign-seek to identify the means of guaranteeing their national sovereignty, including through their various alliance systems. In France, the notion of European sovereignty, absent from the four previous Defense White Papers, appears for the first time in the 2022 RNS (three occurrences) and again in the 2025 RNS (four occurrences). This slippage, in a national document that seems to be orchestrating its own obsolescence, warrants a thorough strategic review.