The temporary suspension of U.S. military intelligence sharing with Ukraine in March 2025 had immediate operational consequences on the battlefield and triggered political turmoil across Europe, bringing the debate over European nuclear deterrence back to the forefront for the first time since the Cold War.

When Washington halted intelligence support to Kyiv for several days, Ukrainian forces reportedly suffered significant setbacks, while European governments reacted with concern. Although the interruption was brief, the signal was clear: the United States is no longer viewed as an unquestioningly reliable military partner.

According to sources familiar with the discussions cited by Bloomberg, European capitals are now holding bilateral and trilateral talks—particularly at the military level—on how to strengthen or potentially establish a European nuclear deterrent. These conversations are taking place discreetly, mainly among countries that host U.S. military assets, are geographically close to Russia, and perceive a direct threat from President Vladimir Putin.

At present, Europe relies on the U.S. “nuclear umbrella,” which includes American nuclear weapons stationed on the continent and NATO’s collective defence clause. If the credibility of that commitment is called into question, Europe could find itself facing Russia—owner of the world’s largest nuclear arsenal—without guaranteed U.S. backing.

Only France and the United Kingdom possess nuclear weapons

Within Europe, only France and the United Kingdom maintain nuclear arsenals. French President Emmanuel Macron is expected to revisit the prospect of extending France’s nuclear deterrent to other European countries in an upcoming speech, following consultations with advisers. He had already signalled openness to such a possibility last year amid developments in Ukraine.

The United Kingdom remains heavily reliant on a U.S. supply chain: its Trident missiles are manufactured by Lockheed Martin, although its submarines are built domestically and London retains operational control. France, by contrast, maintains full sovereign capability, including the production of its own nuclear warheads.

In theory, other European states could pursue nuclear weapons programs, but doing so would entail substantial economic and political costs, including breaching international non-proliferation agreements. Alternatively, they would have to accept that extending nuclear protection to an ally carries the inherent risk of becoming a target of retaliation.

“Imagine Russia invading Estonia,” said Pavel Podvig, a researcher at the United Nations Institute for Disarmament Research. “France has the capacity to inflict enormous damage on Russia, but Russia could inflict comparable damage on France. Would Paris be willing to take that risk?”

Nuclear deterrence at the heart of the Munich debate

The issue of nuclear deterrence is also expected to feature prominently at the Munich Security Conference. However, many experts argue that fully replacing the U.S. nuclear umbrella would be financially unsustainable. In 2025, the European Union and the United Kingdom together spent more than $530 billion on defence—an amount already placing significant pressure on national budgets.

Daria Dolzikova of the Royal United Services Institute considers the idea of a unified pan-European nuclear deterrent unrealistic. “I don’t see a single European nuclear deterrent emerging,” she said, adding that the more plausible question is how French and British nuclear strategies could contribute more effectively to Europe’s overall security framework.

France and the United Kingdom together deploy roughly 400 nuclear warheads, compared with approximately 1,670 deployed by the United States. While smaller in number, their arsenals are still capable of devastating destruction. Russia, however, maintains a broader spectrum of nuclear options, including a significant stockpile of tactical nuclear weapons.

France and the United Kingdom each spend an estimated $12 billion annually to maintain their nuclear forces. Domestic political dynamics could also complicate any move to extend deterrence. In France, for example, figures such as Marine Le Pen and Jordan Bardella have expressed opposition to the idea of “shared” nuclear deterrence.

NATO stresses unity

NATO has sought to project unity. Secretary General Mark Rutte has reiterated that the United States remains committed to the transatlantic alliance, while a Pentagon official stated that U.S. nuclear deterrence commitments to allies continue unchanged. President Donald Trump has not publicly addressed the nuclear umbrella issue, and, according to sources, it has not featured prominently in private discussions.

Despite the renewed debate, many analysts believe economic constraints and political divisions will limit Europe’s ambitions. “If you want a multi-layered nuclear umbrella, you are on the path to becoming a global power,” Belgian Prime Minister Bart De Wever said. “I’m not sure Europe needs to go that far.”