If a nuclear arms race begins, it will be unstoppable.

The world is on the brink of a new nuclear arms race. If it is to be avoided, one of the main reasons will be this: at this point, the first country to go down that path risks paying a terrible price. Rogue countries caught rushing to the bomb will face devastating sanctions and military strikes. And any even somewhat respectable country that violates the Nuclear Non-Proliferation Treaty—the legal ban on the creation of new nuclear forces, signed by 191 countries—risks international isolation, with incalculable economic and diplomatic consequences.

Less comforting is the idea that – if it does start – the nuclear arms race would continue to spread like dominoes falling one after another. This is not the panicked assessment of this columnist. This is the view of the world's top nuclear watchdog, Rafael Mariano Grossi, who calmly expressed it on April 13 in an interview with "Inside Geopolitics", a video show produced by the British "The Economist".

As director general of the International Atomic Energy Agency (IAEA), Grossi is tasked with persuading states not to violate nuclear weapons restrictions and to sound the alarm if they try. Asked if he is concerned about a potential nuclear arms race, the veteran Argentine diplomat says: “I am indeed concerned.” Can he confirm reports that many countries, far from the public eye, are discussing acquiring nuclear weapons — be it Iran’s neighbors in the Persian Gulf or US allies like Germany, Japan, Poland or South Korea, who are no longer confident that they are protected by the US nuclear umbrella? “These discussions are taking place,” he replies.

Grossi acknowledges that the existing nuclear non-proliferation regime has failed over the years to prevent several states from joining the nuclear club. Still, he calls it “one of the last points of stability we still have” in a dangerous world. If more countries start building nuclear arsenals, a domino effect will “inevitably” lead “a good number of states” to do the same, he warns.

Grossi laments the strategy of nuclear bluff that has led Iran to its current grim fate. He recalls how the Iranian regime boasted that it possessed all the elements needed to build a nuclear bomb, including uranium enriched to near weapons-grade levels, while simultaneously asking the world to believe that it never intended to build bombs or warheads.

He does not confirm the American and Israeli claims that Iran was on the verge of a nuclear breakthrough. Instead, he describes how he unsuccessfully appealed to the Iranian authorities to allow IAEA inspectors the full access that the country’s large and ambitious nuclear program required, because in the atomic world “promises are not enough.” Unfortunately, Iran’s leaders preferred to stick to a policy of ambiguity and, as Grossi says, America and Israel eventually ran out of patience. In a conference room on the 28th floor of a United Nations skyscraper in Vienna, Grossi takes stock of Iran’s fatal gamble. He recalls tours of Iran’s underground nuclear facilities that have since been reduced to rubble, as well as conversations with Iranian officials and scientists who were later killed in air strikes and assassinations.

The IAEA chief believes that the deaths of Middle Eastern rulers who sought nuclear weapons in Iran, Iraq and Libya provide a clear lesson: regimes with nuclear ambitions should return to the negotiating table. He is too diplomatic to mention Israel's undeclared nuclear arsenal and the anxiety it causes in some of its neighbors.

Others, however, draw quite the opposite conclusion. One European diplomat, who frequently talks to governments across the continent about nuclear strategy, describes the cynical mood that gripped European capitals after Russia's invasion of Ukraine in 2022, and which intensified after Donald Trump's return to power last year.

Behind closed doors, European officials agree on one thing: “Ukraine would not have been attacked if it had nuclear weapons.” Yes, Grossi is “absolutely right” when he says that the world as a whole is safer without the further spread of nuclear weapons. “But look at the interests of individual states,” the diplomat warns.

The rulers of Iran, Iraq and Libya negotiated with the West about their nuclear programs. All are dead. “The one who is alive is Kim Jong Un,” the North Korean despot who defied the world to build intercontinental ballistic missiles with nuclear warheads. The diplomat lists a dozen countries believed to be seriously considering nuclear options — from northern Europe to Indonesia, Turkey and the United Arab Emirates. “I never want to see a nuclear-armed Germany,” says the European diplomat, whose country suffered badly in World War II. But he still predicts that Germany will one day want a nuclear bomb — “and get one, because it can’t rely on the United States, and I can’t believe I’m even saying that.”

Searching for safety in a lonely world

Back in Vienna, Grossi is too experienced to be shocked by regimes that believe they would feel safer if they had nuclear weapons. Instead, he calls for a nuanced analysis of the motives and interests of different states. The argument that nuclear weapons provide protection “is valid for North Korea,” he admits. But Kim Jong-un’s regime has largely resisted pressure from America, China and South Korea, in one corner of northeast Asia. In contrast, he says, the geography and politics of the Middle East create a much more complex dynamic, making it far more dangerous for a country in the region to “burn bridges” and go for the atomic bomb.

Yet even in the Middle East, force is not the only solution. Grossi is convinced that Iran's nuclear program cannot be completely wiped out by bombing, if only because "you can't unlearn what you've already learned." He sees a negotiated settlement as the only way out.

Other diplomats and experts offer a more somber prognosis. As the Gulf war drags on, they see more reason for Iran to try to get a nuclear device, though its program may have to become smaller and more secretive to resist Israeli and American intelligence, and the resulting weapons could be quite primitive. “We could wake up one morning to a flash in the desert,” says one expert. Still, even a simple nuclear explosion sends a message that neighbors will find hard to ignore. The dominoes of proliferation are already teetering. One gentle nudge is all it takes to topple them.