How Close Are We to Nuclear War?

Recent advances in military technology may push us closer to the edge.

On Tuesday, a missile landed in Przewodów, a Polish village near the border with Ukraine. Two people were killed in the blast. Their deaths were a direct consequence of Russia’s ongoing invasion of Ukraine, though in the fog of war it was not immediately clear which side was to blame. Initial theories held that the missile had been fired by Russia at Ukraine and gone astray, though later U.S. intelligence suggested that it had instead been part of an interceptor fired by Ukraine at a Russian missile. Consensus has formed around the latter idea.

If Russia had indeed attacked Poland, the world might look very different today. Poland is a member of NATO, and a deliberate strike on one alliance member demands a response from all. A global conflict could have followed. And in that context, we must contemplate the extreme conclusion: Russia has the world’s largest nuclear arsenal, and there are reasons to believe that the Kremlin might use it.

But no one should rest any easier knowing that the spillover from a defensive strike is to blame for what happened in Poland. Recent advances in defense technology may have, paradoxically, upended the old concept of mutually assured destruction—the idea that the guaranteed annihilation of an aggressor by its nuclear-armed target would prevent such an attack. Instead, by trying to protect ourselves from nuclear weapons, we might be making the threat of them worse.

Although NATO nations, including the United States, have continuously armed Ukraine against Russia, early calls for the United States to create a no-fly zone over the country—essentially a commitment to attack Russian aircraft, should they overfly Ukraine—were rejected by the Biden administration. The risk of starting a shooting war with another nuclear-armed nation, a war that could escalate to a massive and horrifically destructive nuclear exchange, constrains how countries fight and act. It is partly this constraint that has fueled the pursuit of new technologies to bypass the hard problems of nuclear war.

Nuclear arsenals create a shared sense of vulnerability among the leaders of nuclear-armed nations. But the development of missile-defense technologies unbalances the equation in a number of important ways. One, good defense reduces the nuclear threat faced by a given nation, which could be emboldened to use its own weapons. Two, facing an advanced missile-defense system might lead an attacker to simply use more weapons in a bid to overwhelm any possible interceptors. And three, a nation that finds itself in an arms race might attempt to speed to the finish line by firing off weapons before an adversary’s defenses are operational. Despite these risks, the United States continues to develop missile defenses: A whole agency at the Pentagon is dedicated to the work.

“You can think of two different levels of effectiveness for missile defenses,” James Acton, a co-director of the Nuclear Policy Program and the Carnegie Endowment for International Peace, told me. “One is Reagan’s dream of the hermetically sealed bubble around the U.S. that could never be penetrated. Those would be great in my opinion, but they’re completely technically infeasible. The other one is having enough missile defenses to be able to defend against ragged retaliation from those countries, which is potentially extremely destabilizing, because they would be worried that if we did a first strike on them, their surviving missiles would not be able to penetrate our defenses, and that would give them incentives to go first.”

Of course, the weapons are getting better, too. They can be launched from multiple locations, fly below radar, and travel at remarkably high speeds. These advances shorten the time frame to respond after a nuclear attack is detected, thereby transforming how vulnerable leaders may feel in such a moment: It is, in other words, more likely than ever before that a bad decision will be made in haste.

The foreign-policy researchers Keir A. Lieber and Daryl G. Press have said that recent changes in technology—better sensors and data processing, new weapons—herald a new era of nuclear vulnerability. “Nuclear deterrence can be robust, but nothing about it is automatic or ever-lasting,” they wrote in a 2017 paper. Fast and potentially nuclear-armed weapons like hypersonic missiles threaten old protocols designed around the predictable flight paths of intercontinental ballistic missiles, or the familiar radar signatures of bombers.

Kelley Sayler, writing for the Congressional Research Service, noted that analysts have identified two relevant factors here: “the weapon’s short time-of-flight—which, in turn, compresses the timeline for response” and “its unpredictable flight path—which could generate uncertainty about the weapon’s intended target and therefore heighten the risk of miscalculation or unintended escalation in the event of a conflict.”

Hypersonic missiles travel at speeds of Mach 5 or greater, and are harder for existing early-warning systems to see and track. Hypersonic missiles are in development by China, Russia, and the United States, and can carry both nuclear and conventional warheads. This arms race clarifies that the story of nuclear war has always been about a competition between nations to develop superior technology. The United States commissioned research and development of the atomic bomb partly out of a fear that other countries, specifically Nazi Germany, might develop it first.

Over the course of a few years, the Manhattan Project created the durable bones of an entire secret nuclear-weapons complex, with labs to design and iterate nuclear weapons and reactors to refine uranium into plutonium. On July 16, 1945, the first atomic warhead was detonated on what is now White Sands Missile Range in New Mexico. Unwitting atomic victims were created moments later, as fallout reached the sparsely populated scrubland around the site, contaminating the environment, food, and water supplies with radiation. “My outer skin gradually fell off the next few days,” one 89-year-old resident recalled to me decades later.

Then, on August 6, the United States Army Air Forces dropped an atomic bomb on Hiroshima. Three days later, they dropped a second, on Nagasaki. The low estimate, made by the U.S. military in the 1940s, is that the two bombs killed 110,000 people in total. In the 1970s, an international team led by Japan issued a high estimate, of 210,000 killed. While there is an arguably specious postwar narrative that President Harry Truman weighed the cost of the bombing against the cost of invasion, and made an affirmative decision to use the bombs, the technology historian Alex Wellerstein has argued that Truman’s most consequential order came after the fact, on August 10.

“The day after Nagasaki, Truman issued his first affirmative command regarding the bomb: no more strikes without his express authorization. He never issued the order to drop the bombs, but he did issue the order to stop dropping them,” Wellerstein wrote.

All weapons of war are tools in service of a political aim. The decision to give the president direct control over the atomic bomb changed the politics of nuclear warfare, and did so at a time when the United States was the only country to have developed such weapons. This era was short. In 1949, the Soviet Union successfully detonated its first atomic warhead.

Rapid development followed. In 1952 and 1953, respectively, the U.S. and the U.S.S.R. detonated hydrogen bombs—massively more destructive warheads with two nuclear cores packed into a smaller payload. Nuclear armaments expanded beyond bombs dropped by long-range planes to include missiles carried by hidden submarines and intercontinental ballistic missiles, or ICBMs, launched from the ground—weapons that could arc into space and then crash down to Earth thousands of miles away. These three points of origin—air, sea, and land—would become known as the “nuclear triad,” and played an important role in deterrence: By spreading its arsenal out, a world power increased the odds that it could successfully shoot off a retaliatory strike.

The Federation of American Scientists estimates that roughly 12,700 nuclear warheads now exist in the world. The United States and Russia maintain nuclear triads, as they have for decades, with the potential to launch mere minutes after a certified command.

Nuclear weapons are unique among military technology because of the scale at which they cause harm, and how that harm inevitably falls on civilians. New weapons and defenses will change the particulars, but the fundamental truth of nuclear arsenals is that they keep the whole world vulnerable.

The prospect of abrupt and sudden destruction, through mistake or panic or anger, hangs over us at all times, so long as the weapons and the means to use them exist. The risks can be mitigated through careful stewardship and calm handling of crises, but it can never be fully removed, nor can it be engineered around.

“I'm leery of big concepts of rethinking deterrence or trying to escape deterrence. I think it is just a feature of life, but neither is it an entirely safe thing. The big issue is how we reduce the likelihood of nuclear use,” Acton said.