Originally published at Financial Times. Archived by Internet Archive

During the cold war, the US and the Soviet Union were at least able to agree on one thing: nuclear proliferation was bad for everyone.

“Haunted” by the thought of a “spiralling nuclear arms race” around the world, US President John F Kennedy initiated talks in the 1960s on what would become the Non-Proliferation Treaty, a bargain between superpowers that has kept nuclear weapons states in single digits to this day.

The containment rested on the US extending its nuclear umbrella to convince allies they need not seek the weapons themselves.

Denis Healey, the late British minister, quipped that US nuclear policy only required “5 per cent credibility to deter the Russians, but 95 per cent to reassure the Europeans”.

Now, under Donald Trump, that assurance has never appeared weaker.

The US president’s pivot to Moscow and scathing disregard for Nato has prompted old allies — from Berlin and Warsaw to Seoul and Tokyo — to confront what was seemingly unthinkable: how to prepare for a potential withdrawal of their US nuclear shield.

“The fraying great power consensus on non-proliferation is real,” said Ankit Panda of the Carnegie Endowment think-tank and author of The New Nuclear Age. “The Trump phenomenon has provided a powerful accelerant for voices in US-allied states who now see nuclear weapons in their own hands as fundamentally solving the problem posed by American unreliability.”

Under the NPT, the number of official nuclear weapons states has been limited to the US, Russia, China, France and the UK — the five permanent members of the UN Security Council. India, Israel and Pakistan, which have never signed the pact, have also developed nuclear weapons, as has North Korea, the one country to leave the NPT.

Trump’s return to power has jolted debate across the western alliance. Analysts fear that if the NPT were to collapse, in part because of the withdrawal of US guarantees, the world may move closer to the 15-25 nuclear weapons states Kennedy foresaw — with a greater risk of a cataclysmic atomic war.

Lawrence Freedman, one of the foremost scholars of nuclear strategy, noted the dilemma for allies is an old one.

France’s weapons programme grew out of Charles de Gaulle’s assessment that Washington was unreliable. China, following its split with the USSR in the 1960s, made a similar calculation about Moscow.

But when US allies doubted Washington in the past, they looked at what developing alternatives entailed and realised that it is “difficult, expensive, and draws attention to themselves”.

“In the end, they lived with it,” Freedman said. “That’s been the position in the past. So the problem is, with the crisis this time of such severity, they’re not sure that they can.”

Germany

Friedrich Merz, Germany’s chancellor-in-waiting, said last month that Europe’s largest nation must now explore “whether nuclear sharing, or at least nuclear security from the UK and France, could also apply to us”.

That call, in itself historic, has triggered an unprecedented public debate that has even seen some analysts publicly ask whether Germany — whose postwar image is constructed around promoting peace in Europe and the world — should seek to obtain its own nuclear weapons.

Germany has hosted US nuclear weapons since 1983. Today, there are roughly 20 US B61 nuclear bombs held at the Büchel air base, about 100km south of the city of Cologne. 

German officials are at pains to stress that the US has given no indication it will withdraw this nuclear shield. Defence minister Boris Pistorius has described the debate as an “escalation in the discussion that we do not need”.

But privately, as they have reeled from the pace of events since Trump took office, some officials have begun wondering aloud whether Germany should consider getting its own nuclear weapons. 

Merz insisted earlier this month that such a scenario would not happen, pointing to two different international treaties that would prohibit it. 

Wolfgang Ischinger, a former German ambassador to Washington, said any real suggestion of Germany becoming a nuclear power would create a “shitstorm of unknown proportions from Moscow, from the [right-wing, anti-German] Law and Justice party in Poland, from other neighbours”.

He added: “We would risk losing most of the trust we have been able to build after the last five or six decades after the catastrophe of world war two.”

But Thorsten Benner, head of the Berlin-based Global Public Policy Institute, is one of several think-tank experts to have floated the idea that the country should at least “invest in maintaining nuclear latency” — a move that would mean putting the infrastructure in place to create a nuclear weapon if necessary without immediately building one.

The discussion, he said, was triggered by concerns about where the UK and France might be headed politically, particularly if Marine Le Pen were to win French elections in 2027. “Both the far left and far right in France are very anti-German and there would be a risk they would not honour a kind of nuclear sharing arrangement,” Benner said. “And then what?”

Poland

The debate in Poland has moved even faster with Prime Minister Donald Tusk this month becoming the country’s first leader to raise the idea of pursuing nuclear weapons, or at least seek a sharing agreement with France.

His political rival President Andrzej Duda responded by telling the Financial Times that it would be better to move US warheads to Poland — a move Moscow would see as a provocation that Washington has long resisted.

“There are suddenly lots of words and different opinions about what to do but they all show Poland believes in stronger nuclear deterrence against Russia,” said Marcin Idzik, a board director of PGZ, Poland’s state-controlled defence manufacturer.

Whether Poland has the ability to follow up on Duda or Tusk’s positions is another matter. US Vice-President JD Vance also told Fox News that he would be “shocked” if Trump agreed to relocate US weapons to Poland.

And while Poland once hosted nuclear warheads during the cold war — for Moscow rather than Washington — it has never had a civil nuclear plant. While it has committed to build one within a decade, it lacks the infrastructure and expertise of other European countries.

Duda argues Poland would need “decades” to develop its own nuclear weapons. That view is broadly shared among analysts and industry executives. Janusz Onyskiewicz, a former Polish defence minister, called Tusk’s proposal “certainly fairly hypothetical and not for the present situation”.

“For us to build nuclear weapons from scratch is too costly and we don’t have enough time to do it,” said Idzik from PGZ. “But if we can be a part of a new European team and nuclear project, of course we want to be part of this.”

South Korea

The unrelenting progress of North Korea’s own nuclear weapons programme, Pyongyang’s blossoming relationship with Moscow, and Trump’s return to power have all fuelled deep anxiety in South Korea over its security.

“Support for South Korea acquiring its own nuclear weapons is broadening, and it is hardening,” said Sangsin Lee, a research fellow at the state-affiliated Korea Institute for National Unification think-tank.

While neither mainstream party has championed such a move, leaders on both sides have advocated the pursuit of “nuclear latency” so Seoul could build or acquire nuclear weapons at short notice.

Oh Se-hoon, the conservative mayor of Seoul tipped as a possible presidential contender, earlier this month called for the US to allow South Korea to acquire a stockpile of nuclear material similar to Japan’s, giving Seoul “nuclear threshold” status.

Oh’s remarks came soon after foreign minister Cho Tae-yul told parliament that acquiring nuclear weapons was “not off the table”. “We must prepare for all possible scenarios,” he said.

South Korea already has the highest density of civil nuclear reactors in the world. “Korea has the basic technology to make nuclear weapons and already has experience of making a very small volume of plutonium and uranium,” said Suh Kyun-ryul, professor emeritus of nuclear engineering at Seoul National University.

“It has the technology to make crude nuclear bombs — similar to those dropped in Hiroshima and Nagasaki — within three months.”

Lee Chun-geun, a researcher at Korea Institute of Science & Technology Evaluation and Planning, said that in addition to acquiring sufficient nuclear material, South Korea would also “need to make a detonator and nuclear warheads, as well as conduct nuclear tests”.

“If it declares a national emergency and mobilises all national resources, it can make nuclear weapons in about two years,” said Lee.

While South Korea has between two and three years’ worth of nuclear material stockpiled, its supply would probably be cut off as a result of withdrawing from the NPT, he said. South Korea’s export economy would also struggle to withstand any economic sanctions that followed.

But Suh of Seoul National University said the Trump presidency offered South Korea a “rare opportunity to negotiate with the US to develop nuclear weapons”.

“South Koreans will ultimately have to choose between being taken over by North Korea or withstanding international sanctions by making its own nuclear bombs, because denuclearising North Korea looks impossible,” said Suh.

Japan

Japan’s unique status as the only country to have been the victim of atomic warfare has made the question of obtaining nuclear weapons, throughout its postwar history, perhaps the greatest political taboo.

At the same time, there has long been a quiet version of the debate in some circles: one that has evolved as North Korea became a nuclear power, China became more militarily assertive, and Trump has thrown into question the reliability of the US nuclear umbrella.

One senior Japanese official said there had always been discussion on the matter among a small group of the most hawkish politicians. “The circle of participants may now be enlarging.”

Japan was an early signatory to the NPT, but its peaceful use of nuclear energy and the opening of an enrichment plant online in the early 1990s has also given it a significant stockpile of material that could be used to build a weapon of its own.

Japan’s massive, sophisticated industrial base, and its leadership in many areas of specialised engineering, say US military experts, mean the physical construction of a weapon would be well within its capabilities, possibly within just a few months of receiving a political green light.

Japan’s most recent report showed that at the end of 2023, Japan held around 8.6 tons of plutonium domestically — enough, in theory, to produce several thousand bombs. That fact has not been lost on China, which has in the past used state media to question Japan’s possession of so much material.

But the psychological and political distance that would need to be bridged to seriously contemplate such a move is, even now, immense. In the Article 9 “peace clause” of its constitution, the Japanese people “forever renounce war as a sovereign right of the nation”: while reinterpretations of the clause have allowed Japan to build and maintain significant conventional military forces, the complexities around a nuclear deterrent remain a stretch.

“For now the whole strategy is built around securing the assurance from the US that Japan still sits under its nuclear umbrella,” said Stephen Nagy, professor of politics and International Studies at the International Christian University of Tokyo. “Plan A is to hug the US. Plan B is to hug the US harder, and so on. Plan Z, at this point, is to obtain nuclear weapons.”

Nagy added that any significant movement on the nuclear debate would also expose Japan’s extreme shortage of strategic thinkers on the issue. The long reliance on the US has, in effect, left only a tiny pool of Japanese experts capable of guiding Japanese policy on the use of nuclear weapons.

That is critical, said Nagy, because of the clear differences between the way the continental US has built the strategy of deterrence and how Japan would have to fashion its own.

Japan, he noted, would receive about five minutes warning in the event of an attack by North Korea or China, versus the 30-minute warning time that the US would have if attacked.

The US as a nation would survive an attack on one or two cities; Japan would in effect be destroyed as a nation if Tokyo and Osaka were annihilated. The taboo in Japan remains strong not just because of what happened in the past, he said, but because questions of nuclear strategy are such a different game, and force such tough questions on the nation.