Europe should build on France’s nuclear deterrent extension offer

An early March 2026 announcement by President Emmanuel Macron that France would expand its nuclear umbrella and extend it to European partners has been lost somewhat amid the attacks by the United States and Israel on Iran. However, the announcement, after years of hints and suggestions, marks a new phase for Europe’s nuclear deterrent.

Countries including Germany, Belgium and Poland have declared their willingness to participate and contribute financially. Talks will also involve the United Kingdom, which has had a framework for nuclear cooperation with France since July 2025. This involves permanent consultations on nuclear strategy, joint patrolling by nuclear-armed submarines and joint R&D.

Operational details remain scarce for now. The agreement between European countries could, for example, be limited to a French commitment to protect participating states, or could involve the stationing of French capabilities in other countries without joint operations. More ambitious approaches could include nuclear sharing modelled on NATO, with allies providing their own planes to carry and deliver French warheads, though this could raise questions about compatibility with long-standing NATO nuclear-sharing agreements.

The end result could involve the extension and joint financing of the French and British deterrents. This model relies on existing arsenals and therefore avoids any need to reform or exit from the Non-Proliferation Treaty. It would expand effective European capabilities by complementing French and British forces with common funding and – potentially – institutionalised consultation. Nonetheless, the deterrent would remain nationally owned and launch authority would stay in Paris and London.

This approach may help in the short term to soothe doubts about the US commitment to Europe. However, it falls short of a proper European deterrent. In particular, the credibility of protection will continue to depend on political will and domestic political considerations in the nuclear-armed states.

First, the guarantor might decide not to fulfil the guarantee when a real threat emerges. Second, even in normal times, domestic political processes might void the guarantee, even if countries have paid for it. In other words, nuclear decisions would remain in the hands of the sitting French president. The system would always remain ‘one bad election away’ from losing its credibility as a deterrent.

Ironically, this is exactly the reasoning – that an external guarantee is never fully credible – that pushed French decision makers to develop autonomous nuclear capabilities in the first place. The risk is inherent in any form of nuclear guarantee provided by an external power. Even within NATO, the re-election of President Donald Trump has seeded doubt and prompted serious discussions among European countries about nuclear protection.

Institutional arrangements could mitigate at least some of these credibility issues. Most straightforward would be a nuclear-sharing agreement, allowing countries to host and jointly operate warheads without formally owning them. This arrangement would tackle some of the doubts about the credibility of commitment during crises, although it would not address the issue of domestic political shifts. During a nuclear crisis, effective nuclear sharing would allow hosting countries to commandeer capabilities even if the guarantor steps back (though in practice this would require tacit consent or advanced decrypting capabilities). However, nuclear sharing does not help if the guarantor withdraws the guarantee in peacetime as a result of a domestic political change.

In the medium term, countries participating in the French plan could pool resources, technical capabilities and command structures to create regionalised nuclear forces (for instance, a northeastern command, a southeastern command and a western command). These would coordinate but remain operationally independent (including for strike decisions), while helping solve credibility and commitment issues by pooling sovereignty among the countries participating in each command. Among these geographically neighbouring, like-minded countries with shared security interests, sovereignty pooling would likely be more acceptable and more credible than at EU or European level, at least in the medium term.

In the long term, the obvious limitations of the French initiative could be addressed by developing the system into a full European nuclear deterrent. This would involve joint ownership, joint governance (which would need to be lean and not veto-based) and joint financing of carriers and delivery vehicles, such as a European submarine fleet.

However, all these features pose enormous organisational, financial and political challenges, and are years away, if ever achievable, requiring a political leap that is today hard to envisage. Nevertheless, public opinion in many EU countries is favourable to the idea of joint European deterrence. Considering the structural worsening of the geopolitical situation and increased uncertainty around US foreign policy, Macron and other European leaders are right to explore an extension of the nuclear deterrent, however preliminary and limited it might be.