Why such a project?
Donald Trump’s arrival in the White House in 2025 sent shockwaves through the European community. The reliability of their greatest ally was called into question, prompting them to re-evaluate their relationship with the United States. In response to the tense meeting between Zelensky and the American President and Vice-President Vance, and the United States’ decision to temporarily suspend its aid to Ukraine, European countries quickly realized the need to ‘take over’ in terms of aid to Ukraine and European security. In early March, France and the United Kingdom agreed to set up a ‘coalition of the willing’ composed of themselves and other countries willing to provide major support to Ukraine in the war and in its protection, as well as in the security of the European continent. At the same time, German Chancellor Friedrich Merz highlighted the problem of American disinterest in NATO and Europe and called on European countries with nuclear weapons to consider a sovereign European alternative. As a result, France and the United Kingdom, the only nuclear powers in Europe, are considering the implementation of a common deterrence strategy that could take over from the Americans in order to reassure Europe about the lack of American commitment and their potential withdrawal.
The stakes are high, as the aim is to guarantee military and economic support and provide a force capable of deterring Russia, but also to defend European partners by positioning itself as a reliable alternative to the American umbrella. The main aim of this project is to coordinate the British and French arsenals so that they can act as a credible deterrent for European allies, independent of American nuclear protection. This will require extending France’s nuclear protection zone, which has so far been concentrated on its national territory and borders, to cover the much larger area represented by the European Union. One of the key issues at stake in this initiative is whether this deterrent force is capable of functioning without American support and whether its capabilities are ‘sufficient’ to defend the whole of Europe. The major question that arises is whether this Franco-British collaboration really has the capacity to deter Russia from a future invasion. Furthermore, can it also provide a nuclear deterrent force for Europe in a context where the United States is losing interest in the continent? What form could this nuclear umbrella take?
This text examines the issue of deterrence and its various forms, as well as the challenge of credibility. It also reviews the fundamental question of deterrence capabilities and means in order to take stock of the European situation with regard to extended deterrence. While the Franco-British project demonstrates great credibility in terms of its nuclear aspect, it is nevertheless necessary for Europe to equip itself with a conventional force that allows for a gradual response at a time when the United States seems to be losing interest in European defence.
Nuclear Deterrence: A Matter of Credibility
Deterrence relies primarily on credibility. The credibility of retaliation, which, through the reaction of the person attacked, will render a potential attack irrational. But also the political credibility of deterrence, which relies on the ability to make the power of one’s weapons credible. Until the end of the Cold War, the various Western and Soviet deterrence paradigms were based ‘solely’ on the manipulation of nuclear weapons. The models of use could be based on a logic of first use or not, but also on a graduated approach or assured destruction. However, they excluded the contribution of conventional means from their escalation schemes. With the progress made in precision weapons, whose success was established during the first Gulf War (Desert Storm), this classic view of nuclear deterrence proved increasingly ineffective. Since the 2000s, the focus has therefore been on developing an integrated deterrence that combines or ‘backs up’ strategic nuclear capabilities with other means. De facto, the imperative of once again having conventional forces available for high-intensity conflict has therefore been reassessed in order to avoid any coup de force or fait accompli that would bypass the threshold of nuclear deterrence. Similarly, the resilience of civil societies is impacted by the risks of disinformation and hybrid warfare. While the core logic of deterrence – the credibility of a response – remains the same, it is now broader than before. To convince an adversary that their aggression would entail costs greater than their immediate attack, it is therefore necessary not only to demonstrate the reliability of nuclear capabilities, but also to signal the preparedness of one’s armed forces and civil society.
In its nuclear dimension, deterrence is theoretically based, in its absolute form, on a triad composed of land, sea and air. Each component provides a means of deploying nuclear force: on land with intercontinental missiles, at sea with submarines, and in the air with bombs carried by aircraft. Although mastery of all three is important, the use of only one or two of the three aspects is sufficient to be credible. In these cases, we can think of the United Kingdom, whose deterrence relies mainly on its naval capabilities, or France, which has both air and sea capabilities. In addition, nuclear weapons can be divided into several types. There are tactical nuclear weapons, but also strategic ones, which have different objectives. The concept of tactical nuclear weapons therefore refers to targeted use with smaller nuclear warheads allowing for precise use on the battlefield, while the strategic objective is to strike and destroy the country’s nerve centres, whether demographic, economic or political. Although there are differences in terms of payload, damage and type of use, the difference between tactical and strategic weapons is mainly in the context of state deterrence doctrines. Furthermore, it is essential to note that the deployment of nuclear deterrence capability does not happen in isolation. The threat of a strike or potential strike must be backed up by conventional means to carry out the operation or demonstrate resilience.
Credibility: The Crux of the Matter
On 10 July, the French President and British Prime Minister announced that they had signed a declaration on the coordination of their respective countries’ nuclear arsenals. Beyond this important symbolic gesture, the question of the credibility of the two countries’ deterrence postures, as well as their resources and capabilities, needs to be clarified in order to ensure the coherence of the European deterrence project. It is therefore necessary to examine the postures of the two main parties involved.
On the French side, nuclear deterrence is based on an ‘all-out’ approach, focusing not on a single enemy, but on the defence of all its vital interests against any adversary. Consequently, French nuclear deterrence is designed to be constant and exclusively defensive. However, it is used as part of a strategy aimed at inflicting unacceptable damage on capitals, important command centres, economic and energy infrastructure, etc. Furthermore, French deterrence is intended to be independent and autonomous, emphasising the fact that it is under the sole authority of the President of the Republic and cannot therefore be used by other countries or entities allied with France. The French concept of nuclear deterrence is centred on the country’s vital interests, which raises doubts about the expansion of French doctrine in its current form. Although the question of European nuclear deterrence is not a new one in France, it is difficult to assess what constitutes a vital interest outside the national territory. Since the Aachen Agreement in 2019, France has committed to protecting Germany by guaranteeing joint defence of the two nations through their military forces, without explicitly mentioning nuclear weapons. Beyond that, doubts remain about France’s political will and its ability to effectively defend countries directly threatened by Russia, even though these countries are calling for nuclear protection, which they see as the only possible means of deterring their common enemy. France would therefore need to revise its entire nuclear doctrine in order to propose a model that marks a break with its past conception of nuclear deterrence.
For the United Kingdom, the deterrence posture involves the use of Trident missiles on a sub-strategic scale. The logic would be to use nuclear weapons in a limited way so as not to trigger a larger-scale exchange. This posture can therefore be situated between the tactical and the strategic, hence the origin of its name. However, the British doctrine of nuclear deterrence seeks to create ambiguity about the circumstances in which the country considers its right to respond with nuclear weapons, allowing it to retain a certain amount of leeway vis-à-vis a potential aggressor. Nevertheless, certain principles are set out. The United Kingdom undertakes not to launch a nuclear strike first and to respond in a minimal but credible manner. Nuclear weapons are therefore purely for deterring potential adversaries and are not considered weapons that can be used on the battlefield. Finally, the United Kingdom has both air and sea-based nuclear forces, although its sea-based forces remain the most effective thanks to the use of its Vanguard-class submarines, which will be replaced from 2028 onwards by the Dreadnought class. However, the British arsenal is ageing and needs to be upgraded, either through the acquisition of airborne capabilities or the modernisation of its weapons. Although the combined arsenals of the two countries (290 for France and 225 for the United Kingdom) do not match the numbers of Russian nuclear weapons (5,580 warheads), the deterrent capability of nuclear weapons, when combined with the countries’ postures and strategies, makes them an effective means of deterring an adversary. However, the question remains as to the political will to act as a guarantor of security for a number of states that are ultimately relatively far from their borders.
The Russian perception of these European projects is also a factor to be taken into account. How do they react to these decisions? The question of a threat posed by European nuclear deterrence is simply not taken seriously in Russian think tanks or media. What emerges mainly is an attempt to discredit European efforts by portraying the British navy as outdated, incapable of fighting the Russians, and composed of immoral individuals. On the French side, the idea is the same: Macron is only looking for a pretext to enter the war and Europe is playing with fire by being a geopolitical player that is no longer serious. Thus, the idea is that Europe is not up to the task and is a bankrupt player struggling to regain its place. However, nuclear weapons still speak for themselves, and the fact that France and the United Kingdom are becoming threats to Russia is well considered. The Deputy Minister of Foreign Affairs of the Russian Federation, Sergei Ryabkov, announced that Russia would take Franco-British efforts into account in its next military planning. It is interesting to note that Russia is seeking to highlight an anti-Russian attitude in France and Europe. In doing so, it hopes to discredit decisions taken by Europe that seek to stir up tensions in order to facilitate the acceptance of its own rearmament by its population. However, the subject of the European deterrence project is not widely discussed in the Foreign Ministry’s press conferences. Nevertheless, at a press conference on 6 March 2025, its spokesperson, Maria Zakharova, mentioned the French project to create a new umbrella, stating that it was impossible due to France’s lesser capacity compared to the American umbrella. However, she also mentioned that this change in doctrine would be taken into account in Russia’s future military planning.
Capabilities that Match Ambitions?
In France, as mentioned above, nuclear deterrence can be understood in terms of two elements: airborne missiles and those installed on submarines. The submarine component is certainly the most reliable and effective, since ballistic missile submarines (SSBNs) are undetectable and untraceable. In addition, among the four SSBNs, there will always be at least one submarine at sea ready to use nuclear weapons, thus ensuring French deterrence. Its capacity to carry 16 M51 missiles per vessel gives it considerable striking power and enables it to fulfil its mission. Thus, the naval component of French deterrence is assured and credible in the eyes of its adversaries. However, the airborne dimension is also a major element of French doctrine. In this case, nuclear weapons are carried on Rafale aircraft stationed at Mont-de-Marsan Air Base 118 and deployed using ASMPA missiles. Nevertheless, France’s airborne nuclear force is located in France in order to defend the country’s vital interests. Although the airborne mission includes refuelling aircraft that allow the Rafales to cover greater distances, these are vulnerable. It is therefore essential that the airborne component be supported by conventional forces capable of defending the nuclear vector. Alternatively, or in parallel, the aircraft could be stationed elsewhere, which would allow them to be closer to the adversary to be deterred and to reach them more quickly. Finally, although we have not mentioned it, it is essential to have increased intelligence capabilities for surveillance and reconnaissance in order for the strategy to be credible. Today, almost all European countries rely on close cooperation with US intelligence, reducing their strategic ‘independence’. For such a mission to be viable, France must secure the support of these allies so that they guarantee the deterrence mission, whether through intelligence sharing (a vital component of nuclear deterrence), conventional support (backing) for carrier aircraft, or by allowing stationing at allied bases in a similar vein to NATO’s nuclear sharing. A major step for France will be to agree on a common doctrine and, in this perspective, the logic of nuclear sharing remains undoubtedly the most relevant, thus allowing allies to contribute while keeping the decision within the French Armed Forces General Staff.
For its part, the British army also ensures its deterrence through a submarine and, more recently, an airborne component. Similarly, the submarine mission requires that there always be at least one Dreadnought-class submarine deployed on mission. However, the nuclear arsenal is equipped with Trident D2 missiles built by the American company Lockheed Martin and capable of carrying up to 12 nuclear warheads. In terms of its air capability, the United Kingdom recently announced the acquisition of 12 F-35s in order to comply with NATO’s dual-capability mission. Concerns have been raised about British deterrence due to the presence of American equipment in its nuclear deterrence capabilities. With Trump’s various announcements, questions have been raised about the strategic autonomy of countries purchasing American equipment. In the case of the UK, this would directly undermine the country’s nuclear capabilities due to its missiles and future aircraft, which are all American products whose margin of strategic autonomy in terms of their use remains unclear. However, the order to fire a nuclear missile rests with the commander of the missile submarine, ruling out any suggestion of American interference or validation. Nevertheless, Washington is partly responsible for maintaining the missiles, which means that cooperation between the two powers on their upkeep must be sustained in order for them to remain functional and usable. Thus, the weapons will continue to function as long as the Americans maintain them. As a result, British deterrence has less room for manoeuvre than the French model, but remains credible and effective. Despite their inferiority in terms of nuclear capability, both models are effective and capable of working together because of their strategies, which seek to strike hard where it hurts. However, conventional support is needed to carry out deterrence, which could be provided by their European allies.
What Can Be Done?
In conclusion, the Franco-British project for a joint European nuclear deterrent offers a solid foundation with real capabilities, characterized by the submarine and ballistic power of both countries and consistent, credible strategic postures which, despite their numerical inferiority, remain appropriate. Their credibility resonates with Russia, as the distrustful regime intends to take this new reality into account in its military planning. The aim of this initiative is to reassure European allies in the face of American disinterest, which risks increasing insecurity for Europe. Furthermore, the management of nuclear security on European territory by European countries allows for a more coherent vision of security that does not rely solely on American capabilities and will. However, the conventional dimension, mainly to support nuclear capabilities in the event of a raid, is still too weak and unreliable, despite deployments in Estonia and Romania respectively to secure the eastern flank. To this end, the coalition could be the guarantor of this force with the support of member countries, which would contribute in part to this dimension. Unfortunately, political uncertainties and a lack of willingness on the part of some countries are slowing down the progress of this project and calling into question the measures taken by the allies.
What should Europe do? The United States is still very important in European defence today, and if Europe wants to be autonomous, it must be able to do without its North American ally. However, this prospect seems unrealistic given the major American involvement in European defence (intelligence, capabilities, etc.). Therefore, it would be more appropriate to see some form of rebalancing. A rise of Europe that ‘takes its destiny into its own hands’ to reduce its dependence on an American presence without completely abandoning it.
To achieve this, Europe as a whole must develop its conventional forces, as some of its members are already doing, such as Poland and, more recently, Germany. But it must also demonstrate greater cohesion and coordination so as not to show any signs of confusion or lack of unity that could undermine the credibility of the project or make it appear to be an empty shell. There is also doubt about the willingness of these Western European countries to actually defend the Eastern nations under this new nuclear umbrella. If Russia were to attack a Baltic country tomorrow, what would France and the United Kingdom do? A nuclear response would obviously not be an option unless the attack itself were nuclear, but a conventional response would also present challenges, hence the need to develop this aspect and establish a relevant doctrine allowing for a gradual and appropriate response. However, the capabilities to do so are not yet in place. Furthermore, rearmament plans do not seem to be scheduled until 2030 to 2035, which is far too long to wait, given that many European actors anticipate a threat as early as 2030 (including France, the United Kingdom, Germany and, more generally, the European countries that have joined the Rearm Europe programme). Europe must therefore invest more and more quickly in its defence, with more immediate measures, as demonstrated by Emmanuel Macron, who has revised French budgets to reach £67 billion by 2027/2030 in order to make this project credible.
So how would nuclear and conventional weapons operate according to this logic? The integration of tactical nuclear weapons into war plans seems unrealistic for European doctrines (unlike the Russian model). As a result, strengthening the conventional component consolidates the support for nuclear weapons, but also allows for a graduated and credible response to an enemy attack, thus enabling greater flexibility for European and transatlantic forces. However, increasing conventional spending is not enough; it is now necessary to develop deterrence models that fully integrate the conventional level alongside the nuclear dimension. The latter requires full coordination between Europeans and, to a lesser extent, with the United States and Canada. It also requires a review of existing strategic doctrines, which are still too focused on nuclear strikes. Conventional forces must therefore become a genuine form of deterrence, allowing for a certain level of gradation in the response. In this way, Europe will be able to ensure its own security. However, the electoral uncertainties hanging over certain European countries are casting a significant shadow over these plans.
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