France’s nuclear initiative: A step toward Europeanising deterrence

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President Emmanuel Macron's speech at the Île Longue submarine base marks a pivotal moment in the evolution of European deterrence. France's announcement that it will expand its nuclear arsenal and deepen nuclear cooperation with key EU partners will contribute to strengthening the credibility of Europe's defence posture. At the same time, the willingness of several European governments to engage in substantial nuclear cooperation with France also reflects a broader shift in European attitudes towards nuclear deterrence. Growing uncertainty about the future of US extended deterrence, together with Russia's nuclear signalling, is forcing many Europeans to consider nuclear deterrence much more seriously. The challenge now is not only implementing deeper nuclear cooperation but ensuring that this progress is matched by stronger conventional capabilities and clear European thinking about escalation dynamics.

France's move builds on a gradual shift in its nuclear policy and in Europe's deterrence debate. For decades, Paris has kept its deterrent strictly national and does not participate in NATO nuclear planning. French Presidents have long signalled that France's vital interests have a European dimension, while maintaining ambiguity over the practical details. In a 2020 speech Macron went beyond previous offers of dialogue by proposing that European partners participate in exercises aimed at building a shared European strategic culture. More recently, France deepened coordination on nuclear issues with the UK through the July 2025 Northwood Declaration.

France's move builds on a gradual shift in its nuclear policy and in Europe's deterrence debate.

Paris is now taking the next step by embedding French nuclear capabilities more openly in Europe's broader deterrence posture (while retaining sole authority over nuclear use). Cooperation with Germany, Poland, the Netherlands, Belgium, Greece, Sweden and Denmark will include a mix of dialogue and consultations, visits to French nuclear sites, partner participation in French exercises and temporary deployments of French nuclear-capable aircraft to partners' bases. Looking ahead, France will also coordinate with allies on how conventional capabilities can support deterrence.

Translating these ambitions into sustained operational cooperation will require overcoming political sensitivities and practical challenges. The prize is a more credible European deterrent posture. The planned expansion and modernisation of France's nuclear arsenal will enhance raw capability. Operational cooperation with allies will also improve the effectiveness of French nuclear forces and therefore support the overall credibility of deterrence. For example, non-nuclear allies could contribute conventional aircraft or other capabilities that support nuclear operations, such as suppressing air defences or escorting nuclear-capable aircraft on sorties and therefore maximising their chances of success. Temporary deployments of nuclear-capable aircraft in partners' territory will make it easier to deploy there in a crisis, facilitating faster crisis response and expanding the geographic flexibility of French jets. Beyond these operational enhancements, France's initiative also promises to strengthen the political credibility of deterrence by drawing allies more closely into its deterrence posture. Greater involvement by European partners in consultations, exercises and operational cooperation signals that the defence of Europe is a shared endeavour.

Of course, the credibility of extended deterrence is never absolute. Russia will continue to question whether France would really be willing to risk nuclear escalation in defence of its allies; or whether a future French government could take a different view. However, France's geographic position within Europe arguably makes its commitment to allies highly credible as its vital interests would inevitably be affected by a conflict in Europe. France's move to make security guarantees to allies more explicit will further complicate adversaries' decision-making. Nevertheless, the credibility of France's extended deterrence would be further reinforced if France increased its military presence in frontline states through deployments of ground forces.

Macron's speech was not only about nuclear capabilities, but about deterrence more broadly. The French President repeatedly highlighted the interplay between conventional and nuclear capabilities - in terms of how allies can contribute to French nuclear deterrence and in terms of how their conventional capabilities contribute to deterrence. This hints at the fact that Europe's main deterrence challenge arguably lies in the interface between conventional and nuclear deterrence, and specifically in the ability to manage escalation in scenarios that fall short of existential threats.

France's initiative promises to strengthen the political credibility of deterrence by drawing allies more closely into its deterrence posture.

In terms of capability, French and British nuclear forces are in principle capable of imposing unacceptable costs on an adversary. However, the most realistic conflict scenario is a rapid Russian offensive against the Baltic states, which establishes a fait accompli through overwhelming local superiority, and then attempts to deter a European counteroffensive by threatening nuclear use. In such circumstances, European leaders would face difficult choices. France's doctrine includes the possibility of a limited nuclear 'final warning', intended to signal resolve and force an adversary to reconsider. Yet crossing the nuclear threshold in response to a conventional invasion would carry the risk of rapid and uncontrolled escalation.

This highlights a broader challenge: to deter Russia Europeans need credible options to impose costs without resorting to nuclear use. That requires much stronger conventional capabilities of all kinds, notably air defences and especially long-range strike capabilities. The ability to conduct precision strikes against military infrastructure, logistics hubs and command nodes at long distance would give Europeans additional tools to impose costs without resorting to nuclear use. Europe's deep precision-strike posture remains limited, not least because stockpiles are thin. However, several states are expanding or modernising their arsenals, and initiatives such as the European Long-Range Strike Approach aim to develop longer-range options. Europeans should accelerate these efforts, while also investing in the intelligence, surveillance and reconnaissance (ISR) infrastructure on which long-range strike capabilities depend.

The changes in France's nuclear posture are an important step toward advancing the gradual Europeanisation of the continent's defence. France's decision to expand and modernise its nuclear arsenal and to deepen cooperation with European partners, coming after the Northwood Declaration and stronger Franco-British coordination, will strengthen the European pillar of deterrence alongside US extended guarantees. Yet nuclear cooperation alone will not resolve Europe's deterrence challenge. The credibility of a more European deterrence posture will depend on Europe's ability to manage escalation below the nuclear threshold, which in turn requires stronger conventional deployments and long-range strike capabilities.

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