When the U.S. briefly stopped sharing battlefield intelligence with Ukraine in March 2025, the results were immediate. Kyiv’s forces suffered decisive setbacks on the battlefield as its European allies watched in horror.

The outage only lasted a few days, but it sent shockwaves through Europe as a new reality dawned: Washington was no longer a reliable military partner, and the continent needed a plan B.

Europe has been fighting to keep an increasingly hostile U.S. in NATO while countries race to rearm. And now for the first time since the end of the Cold War, European capitals are discussing how to develop their own nuclear deterrent, according to people familiar with the matter, citing conversations between militaries and governments.

German Chancellor Friedrich Merz confirmed it was a live issue in a speech on Friday at the Munich Security Conference. “I have begun confidential talks with the French president on European nuclear deterrence,” he said. “We will not allow zones of differing security to emerge in Europe.”

Europe depends on the U.S. for its so-called nuclear umbrella, comprised of American weapons based on the continent and NATO’s mutual defense pact. If the U.S. can no longer be trusted, Europe is faced with the sinister prospect of being home alone with a neighbor, Russia, that owns the world’s largest nuclear arsenal.

At the moment, only the U.K. and France have atomic weapons. French President Emmanuel Macron is expected to offer nuclear deterrence to the rest of Europe in a speech this month, according to people familiar with the matter. He already evoked the possibility of extending the French umbrella over the rest of Europe last year following the events in Ukraine.

With enough money, other European countries theoretically could get nuclear missiles. But that would require painful choices: high costs and international treaty violations if countries want to develop their own arsenal, or the acceptance that signing up to defend an ally comes with the likely trade-off of being attacked themselves.

“Imagine that Russia invades Estonia,” said Pavel Povdig, a senior researcher at the United Nations Institute for Disarmament Research. “So, France has this calculation — they have the capability to do a lot of damage to Russia, but Russia would definitely do a lot of damage to France in response. Would that be something Paris would be willing to contemplate?”

Europe is treading carefully. As officials tackle the issue, they have been mindful of what signs they send to Russia, keeping the conversations in bilateral or trilateral formats among countries that have strong trust, a person familiar with knowledge of the talks said. They declined to be identified because of the sensitivity of the issue.

The countries involved in discussions usually host U.S. military assets, are close to Russia and feel directly threatened by Vladimir Putin, the person with knowledge of the talks said. They are occurring at a deep military level, and even ministers may not be aware, the person added.

Nuclear deterrence is set to be a hot topic in Munich. Macron’s nuclear speech will come later, in France, after consultations with the president’s advisers, according to people familiar with the timing.

Replacing the U.S. “umbrella” with new European weapons is unaffordable for most countries, among other problems, experts said. The continent is already breaking the bank to scale up conventional military power. In 2025, the European Union and the U.K. together spent more than $530 billion on defense, more than half the entire gross domestic product of Poland.

For now, Europe’s best move would be to develop its advanced non-nuclear weapons arsenal, which can threaten valuable targets inside Russia and blunt an invasion, according to Darya Dolzikova, a senior researcher at the Royal United Services Institute.

“I don’t see a pan-European nuclear deterrent,” said Dolzikova, author of a recent report on nuclear deterrence in Europe. “I don’t think that’s feasible. What I do think there is room to do is ask, ‘How do the French and the British think about their own domestic deterrents, and how does that affect European security?’”

France and the U.K. have about 400 deployed warheads between them. That compares with America’s 1,670, a number that could grow following the expiration this month of the New START treaty between the U.S. and Russia that controlled nuclear arms.

Despite their smaller arsenal, the French and British warheads have enough explosive power to destroy hundreds of cities, according to Dolzikova. Russia, by contrast, is more nimble, its vast arsenal including smaller weapons giving it more options for targets and how it responds in any escalation.

The U.K. and France spend about $12 billion together to maintain their weapons each year. That’s more than half the entire defense budget for Sweden, NATO’s newest member.

Convincing voters to accept that pricey nuclear weapons cover other countries — even if the costs didn’t rise — could be a tough sell. Both Paris and London already face taxpayer grumbling as the governments make tough budget choices.

The two countries have been holding discussions on how to better coordinate their nuclear forces. Last year, they signed the Northwood Declaration, which stated: “Our nuclear forces are independent, but can be coordinated and contribute significantly to the overall security of the Alliance, and to the peace and stability of the Euro Atlantic area.”

France could station nuclear-capable fighter jets in other European countries, such as Poland, according to a report by the Paris-based think-tank IFRI. Easier options include increasing the participation of NATO countries in French nuclear exercises, or closer alignment between France and NATO’s Nuclear Planning Group.

Individual countries could invest in “turnkey” capabilities, which means having all elements in place to build a nuclear weapon if needed. But even that requires nuclear power plants, complex and expensive enrichment facilities, and the political willingness to violate non-proliferation agreements, according to a person familiar with Europe’s nuclear discussions.

“It is a very complicated matter because the French nuclear deterrent is not an actual nuclear umbrella like NATO offers us,” Belgian Prime Minister Bart De Wever told Bloomberg. “If you would talk about nuclear weapons, then you talk about spending a lot of money.”

From their partners’ perspective, it’s also not a given that the U.K. and France will always have governments committed to the idea of protecting the rest of Europe, said IFRI researcher Heloise Fayet. France is due to hold a presidential election next year, and Marine Le Pen and her right-hand man Jordan Bardella have vocally protested against any idea of sharing the nuclear deterrent.

“Our allies may come to think that they cannot rely on us,” said Fayet. “Credibility requires acting quickly and fast to create habits.”

NATO, meanwhile, is doubling down on its messaging of unity. Secretary-General Mark Rutte has said repeatedly that the Americans remain fully committed to the transatlantic alliance. A Defense Department official in Washington said the U.S. continues to extend nuclear deterrence to its allies.

Indeed, when the U.S. talks about Europe handling its own security, it’s about conventional defense. President Donald Trump has not mentioned the nuclear umbrella and the U.S. has not broached the subject in private either, according to people familiar with the matter. The White House didn’t respond to a request for comment.

For its part, the U.K.’s arsenal is deeply linked to the U.S. Although the U.K. has operational independence of its nuclear deterrent, and the submarines are British-made, its missiles are built by U.S. defense firm Lockheed Martin Corp.

Unlike France, the U.K. has also assigned its nuclear deterrent to the defense of NATO since 1962, the only European nation to do so. That means it doesn’t need to negotiate and sign bilateral umbrella agreements with other members.

But the challenges and costs of developing nuclear arms to rival the U.S. will most likely keep European goals more modest. “If you want a multi-layered nuclear umbrella then you are very hard en route to becoming a world power,” Belgium’s De Wever said. “I am not sure if Europe has to go all the way.”

--------

—With assistance from Ellen Milligan.

©2026 Bloomberg L.P. Visit bloomberg.com. Distributed by Tribune Content Agency, LLC.