On May 22, 1972, Richard Nixon stepped off Air Force One in Moscow and made history as the first American president to set foot on Soviet soil. Only a decade earlier, the Cuban missile crisis had brought the two superpowers to the edge of a nuclear war. Now Nixon and Soviet leader Leonid Brezhnev had chosen a different path, to put an end to the nuclear arms race. But putting a ceiling on the most dangerous weapons ever built was not an easy matter for either man. Nixon was a lifelong anti-communist, sitting down to negotiate limits with the very empire he had spent a career denouncing. Brezhnev, for his part, was neither a liberal reformer nor a man given to sentimentality.
After two days of talks, Brezhnev settled on an unusual diplomatic manoeuvre. He grabbed Nixon by the arm, took the wheel of the 1972 Cadillac Eldorado he had just been gifted by the American president, and drove out of the Kremlin gates, leaving the Secret Service, in Henry Kissinger's words, "beside themselves”. Stripped of advisers and protocol, the two leaders found space for a conversation the formal table had never allowed. Forty-eight hours later, in the gilded St Catherine Hall, Nixon sat across from Brezhnev and signed the Strategic Arms Limitation Talks Agreement, the first treaty in history to cap nuclear weapons.
More than five decades on, those guardrails are gone. New START, the last bilateral nuclear treaty between the US and Russia, lapsed in February, removing the final legally binding limits on the world's two largest nuclear arsenals. Together they control roughly 90 per cent of the global nuclear inventory—more than 10,000 warheads, enough to devastate organised human civilisation several times over. For arms control experts, the treaty's demise is not merely the end of a single agreement, but the collapse of five decades of structured nuclear restraint.
Into this already dangerous vacuum has come a second, seismic shock. The US-Israeli war against Iran, justified by its architects as a necessary intervention to permanently derail Tehran's nuclear programme, may paradoxically ignite a perilous global arms race. Iran was not struck because diplomacy had been exhausted, but in the middle of it. As North Korean leader Kim Jong-un says, it was definitive proof that his nation had been right all along to maintain a nuclear stockpile. From Riyadh to Seoul to Warsaw, other governments are absorbing precisely the lesson.
The arms control order that Nixon and Brezhnev inaugurated was imperfect but durable. By the 1980s, as the combined Soviet and American stockpiles had soared to 70,000 nuclear weapons, Ronald Reagan shifted focus from limiting to actively reducing arsenals, giving birth to the START (Strategic Arms Reduction Treaty) framework. Signed in 1991 by George H.W. Bush and Mikhail Gorbachev, it capped each side at 6,000 deployed warheads on no more than 1,600 delivery vehicles. Subsequent agreements tightened those limits progressively.
The capstone was the 2011 New START, negotiated under Barack Obama and Dmitry Medvedev. It capped deployed strategic warheads at 1,550 per side and established a rigorous verification architecture. Before Moscow suspended participation in 2023, the two countries had conducted 328 inspections and exchanged more than 25,000 notifications. Predictability, rather than trust, was the treaty's central achievement.
Despite that record, the Trump administration allowed New START to expire, dismissing it as a “badly negotiated deal”. The principal argument was that any future arms control regime must include China, whose arsenal is expanding rapidly—a tripolar nuclear order, in Washington's view, that made bilateral constraints with Russia alone strategically obsolete. "The sooner we start talking, the better the chance that we will be able to, once again, start regulating the nuclear arms race before it becomes irreversible,” Nikolai Sokov, senior fellow at the Vienna Center for Disarmament and Non-Proliferation, tells NBC News.
Russia's own role in the collapse is equally significant. Even before the formal expiration, Moscow hollowed out the agreement from within, suspending the verification regime and developing systems designed to circumvent US missile defences. Russia simultaneously engaged in overt nuclear brinkmanship during the Ukraine war, issuing thinly veiled threats about tactical nuclear use and thereby weakening the long-standing global taboo against nuclear coercion.
It is against this backdrop that the Iran war delivered its proliferation shock. For Iran itself, the strikes appear to have accelerated its nuclear timeline rather than halted it. Prior to the conflict, US intelligence and the International Atomic Energy Agency agreed that Iran was not actively building a weapon, having adhered fully to the 2015 Joint Comprehensive Plan of Action until the US unilaterally withdrew. With Iran's inventory of ballistic missiles—its primary conventional deterrent—heavily degraded by US and Israeli attacks, acquiring a nuclear weapon is now viewed as the fastest route to restoring deterrence. Prominent voices in Tehran are openly advocating that Iran exit the Non-Proliferation Treaty. A nuclear arsenal is now perceived as "the only thing that will guarantee regime survival”.
The historical pattern reinforcing this logic is difficult to refute. Leaders who voluntarily abandoned their nuclear programmes—Libya's Muammar Gaddafi and Iraq's Saddam Hussein—were subsequently toppled by the US. A nuclear-armed North Korea, by contrast, has remained secure from direct attack. These precedents were already well known. What the Iran war added was a new and more chilling dimension: that engagement itself offers no protection. For any state now weighing whether to negotiate with Washington, the message is that even the negotiating table is dangerous.
The shockwaves are radiating outward in every direction. Saudi Arabia's Crown Prince Mohammed bin Salman has explicitly warned that the kingdom will seek a nuclear weapon if Iran acquires one. Analysts predict Turkey and Egypt will not be far behind. In East Asia, fears over North Korea's expanding arsenal and China's ambitions regarding Taiwan had already driven nuclear debates long before the Iran war compounded them. To manage the Middle Eastern conflict, the US reportedly redeployed part of its THAAD missile defence systems from South Korea—a visible signal to Asian allies that Washington is dangerously overextended. Public support in South Korea for an indigenous nuclear weapons programme has surged to a record 76.2 per cent. In Japan, the historic taboo against nuclear weapons is fracturing, prompting China and Russia to warn that a nuclear Japan would "bring disaster to the world”.
In Europe, meanwhile, Emmanuel Macron has publicly floated extending the nuclear umbrella to allies, attracting serious interest in Berlin and Warsaw. Nations reeling from Trump's repeated denigration of NATO and his musings about seizing Greenland are asking whether American security guarantees can still be taken at face value. "When one state takes steps to increase its security, others often feel less secure and respond in ways that leave everyone worse off," notes Monica Duffy Toft of Tufts University's Fletcher School. "Arms control agreements emerged precisely to dampen this dynamic, by clarifying capabilities and intentions and reducing incentives to assume the worst." That dampening mechanism no longer exists.
Without legally binding ceilings, the US, Russia and China are free to expand both the size and composition of their arsenal. Washington has already allocated funding towards reopening previously deactivated missile tubes on its Ohio-class submarines, potentially increasing deployed warheads by nearly 2,000 within a decade. Russia, maintaining a substantial reserve of non-deployed warheads, could match or exceed such uploads. Discussions in Washington about resuming underground nuclear testing—the US has not conducted an explosive test since 1992—threaten to shatter the global testing moratorium.
The erosion of superpower restraint also imperils the 1970 Nuclear Non-Proliferation Treaty. Non-nuclear signatories accepted permanent renunciation of atomic weapons on the understanding that the recognised nuclear powers would pursue good-faith disarmament. The sheer ambiguity of current US policy—a president describing proliferation as a major problem while suggesting Japan and South Korea should consider acquiring their own weapons—risks normalising what was once a fundamental red line. The IAEA has warned that over 20 countries currently possess the industrial bases, energy programmes and engineering expertise necessary to build a bomb. "The non-proliferation regime has survived difficult periods before," writes Georgia Cole of the London-based Royal Institute of International Affairs. "But it cannot survive indefinitely if the major powers continue to signal through their actions that nuclear weapons remain the only reliable guarantee of security."
Nixon and Brezhnev proved that even adversaries locked in ideological conflict could impose ceilings on the most destructive weapons ever created. What they built was imperfect and contested, but it held for half a century. What has replaced it is something altogether different: a world in which the great powers expand their arsenals without legal constraint, in which threshold states draw their own lessons from the ruins of Iranian diplomacy, and in which the alliances and treaties that once gave non-nuclear governments reason to hold back are fraying at every seam. As Alexandra Bell, president of the Bulletin of the Atomic Scientists, tells the Guardian: "Nuclear risks have become more complex, more dangerous, and we have seen leaders fail in their obligation to manage those risks." The guardrails are gone. And those who have taken note—in Tehran, Riyadh, Seoul and beyond—may not just be waiting to see what comes next.