Get Ready for the Next Nuclear Age
How Trump Might Drive Proliferation
Foreign Affairs/Gideon Rose
March 8, 2025As the second Trump administration rapidly dismantles crucial elements of the postwar international order, it seems not to have considered some obvious possible consequences of its actions—such as the triggering of a new round of nuclear proliferation, this time not by terrorists or rogues but by the countries formerly known as U.S. allies.
Turning back the foreign policy clock a century won’t erase the existential threat we contend with today: namely, widespread nuclear expertise and relatively cheap, easy nuclear technology. The nonproliferation regime that keeps widespread acquisition of nuclear weapons at bay is a voluntary act of concerted national self-restriction, one that countries adhere to because they feel safer with that regime than they would without it. But they feel safe in large part because the regime is nestled within a broader international system policed by generally benign American power. It is this web of cooperative international partnerships, including institutions such as NATO, that the Trump administration is currently shredding.
Everyone should understand that if the liberal order falls, the nonproliferation regime would fall with it. And the powers rushing for nukes then would be newly orphaned friends of the United States who are no longer convinced they can rely on American security guarantees, and might even have to fear American coercion.
The political scientist Kenneth Waltz famously argued that when it came to the spread of nuclear weapons, “more may be better”—because all international rivalries would be durably stabilized by the prospect of mutually assured destruction. The world may be about to test his hypothesis. And since the most dangerous phase of the proliferation process is always the period when countries are about to cross the nuclear threshold, unless the Trump administration changes course, the years ahead are likely to be defined by nuclear crises.
WHAT GAULLE
American policymakers began building a rules-based international order during the 1940s, after three decades of war and economic crisis. The lesson they drew from the first half of the twentieth century was simple: acting purely on crude short-term self-interest led countries to embrace beggar-thy-neighbor economic policies and buck-passing security policies, which in turn produced economic and social turmoil, the rise of aggressive autocracies, and, ultimately, global carnage. Hoping to avoid a repeat of this pattern, Washington decided to try acting on enlightened long-term interest instead, playing international politics as a team sport. This meant working with like-minded allies to build a stable, secure framework within which members of the team could grow together without fear.
From the beginning, the order has rested on extraordinary American power, deployed on behalf of the team at large rather than the United States alone. This has reflected neither sappy altruism nor cynical neoimperialism but an understanding that in the modern world, economics and security need to be handled at something beyond the national level. American policymakers recognized that capitalism is a positive sum game in which the players can grow together rather than at one another’s expense and that among friends, security can be a nonrivalrous good. So instead of using its incredible strength to exploit other countries—as every other previous dominant power had done—Washington chose to jump-start its allies’ economies and support their defense, creating an ever-growing zone of Lockean cooperation within the larger Hobbesian international system.
As the ultimate tools of war, nuclear weapons posed a unique challenge for the order to handle. It seemed likely that countries that acquired them would get strategic autonomy and coercive power, whereas nations that didn’t go nuclear would become prey. Unsurprisingly, lots of countries thought about getting them—as always happens when new military technology appears. But mass proliferation was avoided when a rough solution to the problem emerged in the 1950s and 1960s. The United States would counter its nuclear-armed enemies through deterrence while using its arsenal to protect its friends as well as itself, obviating the need for them to have independent nuclear programs. These arrangements were locked in through the Nuclear Nonproliferation Treaty (NPT) in 1970. The Americans, Soviets, British, French, and Chinese got to keep their arsenals, enabling deterrence to continue to work, while other signatories gave up the right to go nuclear. The bargain made sense and has largely held up ever since, with only Israel, India, Pakistan, and North Korea joining the nuclear club afterward.
If the liberal order falls, the nonproliferation regime would fall with it.
Most of the attention in the nuclear realm has always focused on the superpowers, and after them, on rogues such as North Korea (which went nuclear in 2006), Iraq (which sought an arsenal), and Iran (which is now at the threshold). Thanks to recent events, however, the often-overlooked British and French cases merit more attention. The United Kingdom started the world’s first nuclear weapons program in 1941, merging it with the Manhattan Project two years later. When Washington stopped cooperating after the war, London decided to continue on its own and successfully tested its first bomb in 1952. France, meanwhile, began a secret military nuclear program in 1954, brought it public in 1958, and successfully tested its first weapon in 1960.
Why did France get the bomb when it was already covered by the American nuclear umbrella? Because French President Charles de Gaulle simply didn’t trust Washington to live up to its security guarantees. Extended deterrence was a sham, he felt, and for Paris to be truly secure, it had no choice but to acquire a nuclear capability of its own. As he put it in 1963, “American nuclear weapons remain the essential guarantee of world peace. . . . But it remains that American nuclear power does not necessarily respond immediately to all the eventualities concerning Europe and France. Thus . . . [we have decided] to equip ourselves with an atomic force that is unique to us.” The French called this the force de frappe—the “strike force.”
For generations, most non-French analysts have scoffed at this reasoning, seeing it as reflecting excessive Gallic pride or paranoia rather than sober strategic logic. After the first weeks of the second Trump administration, it seems prescient, and few are scoffing now.
TO RUSSIA WITH LOVE
With the end of the Cold War and the breakup of the Soviet Union, the nuclear picture changed significantly. The chance of a superpower confrontation now seemed remote, and the most urgent threats seemed to come from the dispersion of former Soviet nuclear materials and expertise to other countries or subnational groups. Corralling “loose nukes” became the problem of the day, addressed by programs such as the one established by the 1991 Nunn-Lugar Cooperative Threat Reduction Act.
A particularly thorny issue was raised by the remnants of the Soviet nuclear arsenal stationed in the now independent country of Ukraine. Other countries pressured Kyiv to give all those remnants back to Moscow, promising that it would not suffer from doing so. Without much ability to resist, Kyiv agreed, and the move was codified in the 1994 Budapest Memorandum, with Belarus, Kazakhstan, and Ukraine joining the NPT in return for assurances of protection by the United States, the United Kingdom, and Russia.
At the time, some argued that this was a mistake. Writing in Foreign Affairs in 1993, for example, the political scientist John Mearsheimer noted that Ukraine would eventually need to counter Russian revanchism and that maintaining a nuclear capability was the least problematic way of doing that. “Ukraine cannot defend itself against a nuclear-armed Russia with conventional weapons, and no state, including the United States, is going to extend to it a meaningful security guarantee,” he wrote. “Ukrainian nuclear weapons are the only reliable deterrent to Russian aggression.” But fears of nuclear proliferation outweighed fears of future wars, so post-Soviet Ukraine ended up with a purely conventional military.
For two decades, this didn’t seem much of a problem. Then, in 2014, outraged by Ukraine’s increasing turn to the West, Russian President Vladimir Putin decided to teach Kyiv a lesson. He fomented separatist movements in southern and southeastern Ukrainian provinces with Russian-speaking populations and then sent Russian forces in to “assist” them, quickly seizing Crimea and parts of the Donbas. Low-level conflict and inconclusive negotiations dragged on for years afterward, until in 2022 Putin launched a full-scale invasion designed to conquer the rest of the country with the intention of either reabsorbing it into Russia proper or reducing it to a colony with a puppet government taking orders from Moscow.
Given the disparity in size and strength between the belligerents, few expected Ukraine to be able to resist the Russian onslaught. But it did, and once it was clear Kyiv wouldn’t fall quickly, the United States and Europe moved to support it with increasing amounts of military and economic aid. As the months and years ground on, a war of movement turned into a war of position and attrition, with Russia continuing to hold Crimea and most of the Donbas while Ukraine clung to a patch of Russian territory near Kursk. The Biden administration and its European allies remained committed to keeping Kyiv in the fight, but Putin’s willingness to throw all his country’s massive resources into the balance increasingly gave him a slight advantage.
Then came Trump’s return to the White House. In running for another term, he had declared his intention to end the war in a day, without saying much about how. Since he took office, the details of his administration’s plans have started to be filled in, and they seem to involve simply forcing Ukraine to accept Russia’s demands: ceded territory, military weakness, a change of government, and reorientation back to the east. It is hard to know just how far the administration’s pro-Moscow tilt will go, both because of the confusion surrounding what appears to be an epochal shift in U.S. foreign policy as well as the inconsistency of the Trump administration’s communications. But in recent weeks, enough has changed to make clear that previous American promises of support, to Ukraine and others, can no longer be fully trusted.
Like de Gaulle, Mearsheimer has been proven right. Extended deterrence was a sham, and the people who relied on it were suckers. Which, for many countries under threat, raises the question: Why not follow the French route and secure themselves by developing their own forces de frappe?
WHO’S NEXT?
Now that the United States has become an unreliable ally, one path that countries seeking protection could take is resourcing extended deterrence from a different provider. The incoming German prime minister, Friedrich Merz, for example, has said that he would “talk to the British and French about whether their nuclear protection could also be extended to us”; other members of NATO might well do the same. British Prime Minister Keir Starmer and French President Emmanuel Macron are open to the idea; a truly European deterrent might soon emerge.
That would be a useful development, helping stabilize European security in a post-American world. But a betrayal by Washington would cast doubt on all future extended deterrence arrangements, making clear they were disposable rather than dependable. Back in the day, London didn’t trust Washington to defend it, and Paris didn’t trust Washington or London. So why should other countries trust London and Paris now? After all: fool me twice, shame on me.
A few countries might therefore decide to pursue their own bombs, just to be sure. With all the restrictions now in place to prevent such an outcome, it would not be an easy course to follow. It would mean assembling serious nuclear expertise, large amounts of fissile material, and the ability to manufacture high-end weapons. It would take several years of sustained effort and cost tens of billions of dollars. But it is certainly possible.
Israel started its nuclear weapons program in the 1950s, receiving lots of help from the French. The Israelis are thought to have developed their first bomb by the end of the 1960s, adding a couple of hundred more in later decades. After watching its archenemy India go nuclear, meanwhile, Pakistan started its covert nuclear program in the 1970s. After getting lots of help from China and North Korea, Islamabad tested a weapon successfully in 1998.
If Seoul went nuclear, Tokyo would probably follow.
Japan has followed a different route, developing a latent nuclear capability rather than a full-blown one—a “bomb in the basement” that could be assembled into a weapon quickly if necessary. Since the 1960s, Tokyo has pledged not to possess nuclear weapons, not to produce them, and not to allow them on Japanese soil. But it has also acquired an advanced civilian nuclear energy program, large stockpiles of separated plutonium, and an impressive local defense industry. Any Japanese government could take the final steps to nuclear armament within months, if willing to accept the controversy that would follow at home and abroad.
So who might go nuclear next? The most obvious candidates would be Ukraine and Taiwan, nations clearly threatened by powerful nuclear-armed neighbors. (Taiwan has already tried twice, in the 1970s and 1980s, but was caught and stopped by the United States each time.) But once such efforts were underway, those neighbors might very well attack before they were completed: the attempt to gain security could easily lead to preventive war and national destruction. Iran might face similar dangers if it moved to cross the final threshold toward weaponization, triggering an American or Israeli attack before it could be sure of its deterrent.
If the order continues to erode, South Korea would probably become the first new nuclear power of this wave of proliferation. It joined the NPT in 1975, but it could withdraw at will and might conclude that it needs an independent nuclear capability to hold off the threat from North Korea. South Korean officials have already begun talking about the possibility, and such discussions would surely intensify if the United States made any moves toward disengagement. If Seoul went nuclear, Tokyo would probably follow. And eventually Australia might join them, restarting the nuclear weapons program it gave up in the 1970s.
In Europe, some Polish generals have been openly mulling the idea of going beyond relying on France and the United Kingdom and acquiring their own nuclear force. In a March 7 speech to the Polish parliament, Prime Minister Donald Tusk seemed to back the idea. Poland “must reach for the most modern possibilities, also related to nuclear weapons and modern unconventional weapons,” he said. “It is not enough to purchase conventional weapons, the most traditional ones.” Meanwhile, officials in Nordic and Baltic countries have surely been having conversations about nuclearization in private. (Sweden had an independent nuclear program into the 1970s.)
None of this is certain, not least because nobody yet knows whether the Trump administration will actually go so far as to abandon the alliances its predecessors built up over generations. But if it does, nobody should be surprised if the former allies reconsider some of the choices they made on the assumption of sustained American protection. It is far too soon to predict how this strange new world will play out. But the psychological barriers that have long kept proliferation at bay may already have fallen away.
