U.S. allies around the world are warming to the idea of developing their own nuclear weapons, the result of a growing sense that U.S. President Donald Trump may abandon key international security commitments and alliances, former senior defense and White House officials told Defense One.
Decades of nonproliferation efforts to persuade countries to forgo nuclear weapons, work led by the United States through security guarantees, are on the verge of collapse, the officials said. Should one or two nations launch nuclear projects, others may quickly follow. That could provoke a military response from Russia or China, which might touch off yet more nuclear development in a self-reinforcing, destabilizing cycle.
What’s changed in the last two weeks?
“The Trump administration’s approach to Ukraine and Russia has significantly undercut allied confidence in the United States, including on extended [nuclear] deterrence,” Eric Brewer, a former director for counterproliferation at the National Security Council. “Not only is [Trump] pivoting away from allies but he’s seemingly pivoting toward Russia.”
The shift has shaken U.S. allies. France—the only NATO member with a nuclear arsenal that doesn’t depend on U.S. technology—hastened to shore up European deterrence by proposing to extend its nuclear “umbrella” to other countries.
“I have decided to open the strategic debate on the protection of our European continental allies through our deterrence,” French President Emmanuel Macron said last week.
Leaders from Bonn to the Baltics quickly praised the idea.
German Chancellor-in-waiting Friedrich Merz on Sunday said, “We should talk with both countries [France and Britain], always also from the perspective of supplementing the American nuclear shield, which we of course want to see maintained.”
But the French proposal leaves many questions unanswered. If France is to convince other nations to huddle under its nuclear umbrella, said one former senior White House senior official who worked on nuclear issues, Paris will need to launch a diplomatic campaign and be willing to share a great deal more information, including classified information, about nuclear decision-making and capabilities—much as the United States did in the 1960s.
In the past, similar proposals have led NATO allies to begin talks, but they collapsed over issues such as who would control the weapons, a former senior defense official said.
“There’s just a lot of questions here about what the French are offering, whether they may really be willing to provide a dual key with Germany for weapons if they put them on German territory for instance. I suspect not,” they said.
Indeed, soon after his initial announcement, Macron clarified that France would not share its warheads with other countries.
Uncertainty
France’s nuclear arsenal of about 290 warheads is larger than Britain’s (under 225) but far smaller than Russia’s (nearly 6,000). Neither has Russia’s diversity of warhead sizes and delivery systems. The U.K.’s small and expensive nuclear submarine fleet is undergoing modernization. France has air-launched cruise missiles. Russia has land-based mobile launchers, siloed ICBMs, bombers, and submarines.
There’s a reason Europe made no attempt to keep up with Russia’s weapons development. Western Europe has always relied on the vast U.S. arsenal to deter Russia.
But, the former senior defense official explained, France had a different deterrence strategy: hold just one or two major targets, like Moscow or St. Petersburg, in jeopardy.
The U.S. idea “was that we were going to develop counter-force capability”—that is, weapons to disable or destroy an enemy’s nuclear capability—“try and take out Soviet weapon systems, command and control, leadership; and try and not go after cities if we could avoid it. The French have never had that kind of compunction. The basis of their strategy was ‘tear an arm off the bear.’ They never thought they could really take on the entire Soviet nuclear force.”
In other words, Paris and London can’t destroy Russia’s ability to wage nuclear war—even enough of it to prevent the obliteration of both countries and more of Europe as well. That isn’t particularly reassuring to European leaders who believe that their countries would be a secondary priority for France should Russia attack.
That may be why Poland’s Prime Minister Donald Tusk said Friday that his country must “reach for opportunities related to nuclear weapons”—perhaps hinting at launching its own development effort.
Proliferation triggers
But the real trigger for a new arms race may sit outside of Europe, the officials warned.
All of the former officials we spoke to said that South Korea is the U.S. ally that is furthest along in pursuing a new nuclear weapons program. The country feels “the most pressure right now,” said the former senior White House official. That’s true across South Korea’s political elites, including “the opposition party that may win the next election.”
Should Seoul start hunting for the fuel to build such a device, Tokyo would likely launch a program of its own, they said, since Japan and South Korea are not treaty allies but do have hundreds of years of conflict history.
“I find it hard to believe you’d see a Japan-and-South Korea joint nuclear weapons development project,” said the former senior defense official.
All the officials we spoke to agreed that if one nation starts a nuclear-weapon program, others will likely do so as well.
“Proliferation will beget more proliferation,” said the former senior White House official.
Trump’s recent talk of abandoning treaty allies is not the only change that may push other nations toward nuclearization. He has also hinted that he might withdraw U.S. troops from certain countries, such as Japan or European nations. This would remove a “tripwire” that helps deter foreign attack, the former senior defense official said, and would cause a host government to consider new ways to deter attack on its own.
New arms-control talks?
Yet Trump has also said he wants to reduce global spending on nuclear weapons. Last month, he called for arms-control talks that would slow Chinese and Russian efforts to build nuclear weapons and therefore allow the United States to shrink its own $1.7 trillion nuclear modernization plan.
“There’s no reason for us to be building brand-new nuclear weapons; we already have so many,” he said.
Russian officials responded warmly to the overture, but said that any talks should include European nuclear arsenals as well. That’s likely a non-starter for Europe, especially in the context of Russia’s rapid nuclear modernization, space weaponization, and the breaking of previous commitments on weapons development.
The U.S. president’s record in nuclear diplomacy holds little success. He cancelled the 2018 nuclear deal with Iran, whereupon Tehran began rebuilding its program; today, the country stands closer than ever to a nuclear arsenal.
After trying threats and flattery on Kim Jong Un, “Donald Trump could only add his name to the list of American presidents who had tried and failed to curb North Korea’s nuclear ambitions before him,” the Wilson Center’s Katie Stallard wrote in 2020.
As well, “Trump in his first term tried and failed to bring China into nuclear arms reduction talks when the U.S. and Russia were negotiating an extension of a pact known as New START,” AP wrote last week. “China has rebuffed past American efforts to draw it into nuclear arms talks, saying the U.S. and Russia first need to reduce their much larger arsenals. A government official reiterated that position on Friday.”
And the New START treaty extension? Trump couldn’t bring it over the finish line, but President Biden concluded it in early 2021—and Moscow suspended its participation two years later.
Breakout time
How long would a technologically-advanced country need to develop a nuclear weapon, unconstrained by the sort of sanctions that slowed the North Korean and Iranian efforts?
The officials we spoke to said it was at least one year but likely more. How many years depends on the country. Some, like Germany and Japan, already have access to the nuclear fuel cycle due to their energy sector. The technological know-how is no longer as elusive as it once was. was. But there are other factors.
“A lot more work goes into designing a weapon than just making the necessary fissile material or mastering missile technology. Warhead design, reentry vehicle technology, potential explosive testing to ensure a design works, etc. will all take time,” said the former senior White House official.
Also, any country launching a nuclear weapon program would likely be in violation of the Nonproliferation Treaty or NPT, which would carry its own consequences.
“These things trigger certain cutoffs of U.S. aid and assistance when certain nuclear thresholds are reached,” said Brewer, the former NSC member who is now vice-president of the nonprofit Nuclear Threat Initiative. “And [the NPT] doesn’t differentiate whether that country is an ally or an adversary. And so that would be a challenge that these countries would have to navigate. It’s hard to create a domestic consensus within these countries for proliferation because of these challenges.”
But NPT is only as strong as the will to enforce it. Once one country decides to abandon it, others would likely follow suit, said another former defense official.
“Were South Korea or a Poland or Saudi Arabia to cross the threshold…It seems hard to believe that the NPT could survive.”
The former White House official said many of these proliferation discussions might “come to a head” at next month’s NPT planning committee meeting in New York.
Increased risk of war
One of the biggest concerns among the officials was that China or Russia would likely regard a nuclear program by a U.S. treaty ally as a threat—and act against it.
“It’s hard to believe Russia is going to stand by idly,” said Brewer. “If that were to happen, what exactly they would do, whether it be kinetic or nonkinetic, it is going to produce its own crisis.”
That would make it more vital than ever for the United States to be clear that it will continue to abide by its protection commitments, said the former senior defense official.
“Let’s see whether American officials reiterate the importance of extended deterrence”—that is, the nuclear umbrella over allies and partners. “Frankly, that would be important,” the official said.
A predictable outcome
None of the officials we interviewed could say whether the White House or State Department were adequately staffed to engage in the highly complex diplomatic efforts needed to prevent runaway proliferation, especially at a time when large sections of the federal workforce are being slashed by the Trump administration.
“If cuts impact expertise [in the National Nuclear Security Administration] and [Defense Threat Reduction Agency] offices that help with nuclear detection and nonproliferation at the same time U.S. extended-deterrence policies shift to increase the risk of proliferation,” then the task of monitoring new proliferation efforts and guiding them will be compromised, said the former senior White House official.
But even existing agreements are proving to be far flimsier than their original drafters imagined. Perhaps the most infamous is the 1994 Budapest Memorandum, an agreement between the United States, the United Kingdom, Russia, and Ukraine in which the latter gave up its nuclear weapons in exchange for security guarantees from the others. Russia, of course, abandoned that commitment in March 2014 when it first invaded Ukrainian territory.
That action, more than a decade ago, threatened to collapse nearly half a century of nuclear non-proliferation efforts. Within days, U.S. lawmakers were debating an emergency aid package for Ukraine. Among the staunchest supporters was a handsome, 43-year-old Florida statesman who took to the Senate floor with an urgent plea: the United States must rise to Ukraine’s assistance, lest U.S. weakness usher in a new era of all-for-themselves nuclear proliferation.
“That’s why the Ukrainian situation is so much more important than simply what is happening in Europe. This situation has implications around the world. Countries around the world are considering increasing their defense capabilities, including a nuclear capacity, because they feel threatened by neighbors that have a nuclear capacity themselves,” said Sen. Marco Rubio, R-Fla. “It raises the real risk that over the next two decades you could see an explosion in the number of countries around the world that possess a nuclear weapons capability.”
Rubio, of course, is currently Secretary of State.
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