Just a few months after the U.S. dropped nuclear bombs on Hiroshima and Nagasaki in 1945, it began trying to abolish these horrifying new weapons.
In 1946, the U.S. government proposed decommissioning all of its atomic bombs and putting the related technology under international control if other states would do the same. (The Soviets refused.) A few years later, President Dwight Eisenhower went to the United Nations to deliver his famous his “Atoms for Peace” speech, imploring other countries not to go down the nuclear road.
To strengthen its case, the United States offered its Cold War allies a deal: it would use its arsenal to deter their shared enemies, so that other members of what was then called the Free World wouldn’t need to build their own bombs. To sweeten the bargain, the U.S. offered to help friendly states develop civilian nuclear energy programs.
This arrangement was formalized in 1970 with the creation of the Nuclear Nonproliferation Treaty. Under that agreement, countries that already had nuclear weapons — the U.S., the USSR, the United Kingdom, France and China — got to keep them, but all other signatories pledged to give up their pursuit.
This U.S.-led system for preventing proliferation worked remarkably well. In the last six decades, only four additional countries (Israel, India, Pakistan and North Korea) have developed full-fledged nuclear weapons, although a few others (notably Iran) have come close. Even more importantly, in the 80 years since the U.S. attacks on Japan, no other country has used a nuclear weapon in war.
Yet that remarkable record could soon be broken and all progress lost.
With the U.S. pausing assistance to Ukraine, threatening to abandon NATO unless other members raise their defense spending to 5 percent of GDP (the current U.S. level is 3.5 percent), and walking back its pledges to protect other allies, countries around the world are suddenly scrambling to come up with alternatives. It may be only a matter of time before some of them decide to pursue the ultimate defense.
The signs of this shift are already appearing. Last week, French President Emanuel Macron — declaring, “I want to believe that the United States will remain by our side, but we need to be ready if that were no longer the case” — offered to extend France’s nuclear umbrella over its neighbors. While Macron’s desire to dissuade other European states from going nuclear is laudable, he is unlikely to succeed.
For one thing, Paris has proposed this before, in 2020, and it didn’t go anywhere. The other, more fundamental problem is that recent developments highlight the danger of relying on any another country, be it the U.S. or France, for one’s own security.
That is, after all, exactly what Ukraine did in 1994. In exchange for security guarantees from Washington, London and Moscow, Kyiv gave up the nukes it had inherited from the Soviet Union. We all know how that turned out — following one invasion in 2014 and another in 2022, Russia now controls about 18 percent of Ukraine’s territory, and Washington has just suspended military and intelligence support to Ukraine.
Imagine you’re watching this from Japan or South Korea, which have aggressive, nuclear-armed neighbors and are themselves “threshold nuclear powers” — meaning they lack the bomb but have the technology, know-how and material to assemble one quickly if they choose to. Or pretend you’re another country with a less-advanced domestic nuclear program but the bad luck to live in a very dangerous neighborhood — Eastern Europe, say. Why wouldn’t you decide that now is the time to quickly start building a bomb of your own?
Indeed, that’s just what Poland’s President Donald Tusk suggested doing in a speech to his parliament on Friday.
For most countries, the calculus is not be simple. Nuclear weapons are incredibly dangerous and very unpopular. There’s a powerful taboo against acquiring them, let alone contemplating their use. Getting caught developing them can trigger international pressure, sanctions and ostracization. Some countries, like Germany, have the capacity to quickly build a bomb but probably never will for historical reasons. And some scholars question whether nukes are even that effective at protecting the states that possess them.
It’s true that in a few cases (Israel and Pakistan) nuclear weapons haven’t discouraged enemies from attacking and even invading. But it’s also true that no nuclear-armed government has ever been overthrown by outsiders. This is why many countries around the world continue to view these weapons as the ultimate deterrent and security guarantee.
Can anything stop the outbreak of a new nuclear arms race in the coming months? The best hope would be for the U.S. to reverse course immediately and renew its defense guarantees to its allies around the world. President Trump should clearly reaffirm Washington’s commitment to NATO’s Article V (which obligates all members to treat an attack on one as an attack against them all) and to America’s non-NATO allies like Japan and South Korea. He should also quickly resume robust military and intelligence support for embattled Ukraine.
But even these moves — unlikely as they may be — might not be enough to prevent the world from going nuclear. After all, the U.S. has now made and broken such promises at least once before. Can it be relied on to keep them the next time?
Jonathan Tepperman is the editor-in-chief of The Catalyst and a senior fellow at the George W. Bush Institute. He is the former editor-in-chief of Foreign Policy, the former managing editor of Foreign Affairs, and author of “The Fix: How Countries Use Crises to Solve the World’s Worst Problems.”
