Until very recently, the prospect of nuclear weapons use by a major nuclear power has appeared relatively remote, enabling other issues—terrorism, climate change, Covid—to dominate the global agenda. But that period of relative immunity to Armageddon has drawn to a close and we have entered a New Nuclear Era, in which the risk of nuclear weapons use by the major powers has reemerged as a daily fact of life. We may yet escape their use and the resulting human catastrophe, but only if we oppose the nuclearization of world affairs with the same vigor and determination as has been devoted to overcoming the climate crisis.

During the Cold War, of course, the threat of nuclear weapons use was ever present. Any major clash between the superpowers—say, over Berlin or Cuba—was assumed to harbor a potential for rapid escalation from non-nuclear, “conventional” conflict to nuclear war. After the cuban missile crisis of 1962, in which a nuclear conflagration was barely avoided, the United States and the Soviet Union tried to avoid actions that might lead to a direct clash between them, but both continued to enhance the destructive potential of their respective thermonuclear arsenals. Only with the end of the Cold War and the dissolution of the Soviet Union did the threat of instant annihilation cease being a constant global worry.

In the years following the Cold War, the prospect of a nuclear exchange between the major powers largely disappeared from the agendas of international policy-makers. That does not mean that the danger of nuclear weapons use disappeared entirely: Both the United States and Russia engaged in the continuous modernization of their atomic arsenals; China, India, Israel, and Pakistan expanded their stockpiles; and the US and North Korea exchanged some harsh nuclear threats. But few outside of the military and a small specialist community paid much attention to these developments and the persistent dread of nuclear annihilation—so widespread during the Cold War era—largely evaporated.

With Russia’s invasion of Ukraine, however, all that has changed. We have now entered a period in which the deliberate use of nuclear weapons is again a distinct possibility, and every clash between the major powers carries the risk of nuclear escalation.

The conditions that made this transformation possible—including a renewed emphasis on nuclear war-fighting among the major powers—have been in place for several years, but the decisive shift was propelled by Russian President Vladimir Putin’s multiple threats to employ nuclear weapons against any other state that attempt to impede his drive to subjugate Ukraine.

Putin’s Volley of Threats

Putin’s first such warning came on February 24, the day Russian troops commenced their attack on Ukraine. In a speech announcing the invasion, he warned that any country that “tries to stand in our way” would face consequences “such as you have never seen in your entire history”—language that could only apply to a nuclear holocaust.

If there were any doubt about his meaning, Putin eliminated that three days later in an address condemning the sanctions imposed on Russia by the US and its NATO allies. “Western countries aren’t only taking unfriendly economic actions against our country, but leaders of major NATO countries are making aggressive statements about our country,” Putin told his senior military advisers on February 27. “So, I order to move Russia’s deterrence forces to a special regime of combat duty.”

By “deterrence forces,” Putin meant Russia’s nuclear retaliatory capabilities. Exactly what he intended by “a special regime of combat duty” is less apparent, but most non-governmental experts on Russian nuclear affairs believe he was calling for a higher level of staffing at Russia’s nuclear command posts—a step that would facilitate the rapid launch of atomic weapons should Putin order their use.

Whatever the precise meaning of Putin’s order, it represents a turning point in modern history: the first overt step toward nuclear weapons use in the midst of conflict involving multiple nuclear-armed powers. “Putin’s threat is unprecedented in the post-Cold War era,” said Daryl Kimball, executive director of the Arms Control Association. “There has been no instance in which a US or a Russian leader has raised the alert level of their nuclear forces in the middle of a crisis in order to try to coerce the other side’s behavior.”

Putin again raised the specter of nuclear weapons use in a diplomatic note sent to the United States and other Western powers in mid-April, warning them against the delivery of major weapons systems to Ukraine. A failure to heed this warning, the note said, could lead to “unpredictable consequences”—again, an unmistakable reference to nuclear escalation.

Simply by making these threats, Vladimir Putin has transformed the global strategic environment in ways not seen since the height of the Cold War. Until now, it has largely been assumed that nuclear weapons would be used only as a deterrent, to discourage potential adversaries from even considering a nuclear attack for fear of catastrophic retaliation—a condition widely known as “mutually assured destruction,” or MAD. But now, thanks to Putin, nuclear weapons have been repurposed as instruments of war—as cudgels with which to discourage an opponent from engaging in certain offensive behaviors by threatening horrific consequences to the offender. Whatever the outcome of the conflict in Ukraine, this new or repurposed use of nuclear weapons will remain an inescapable feature of any major-power crisis. And, once the threat of nuclear weapons use has been normalized in this way, it is hard to believe they will not be used, sooner or later, to demonstrate the credibility of threats like those issued by Putin.

But this New Nuclear Era is being defined by not only the normalization of nuclear threats but also the adoption of policies by both the US and Russia that make nuclear weapons use far more practical and conceivable than in the past.

Envisioning Nuclear Weapons Use

To fully appreciate the significance of this shift, we must first consider recent developments in US and Russian nuclear weapons doctrine. By the Cold War’s end, MAD had come to govern the nuclear policies of the two superpowers, enabling them to reach agreement on a series of graduated reductions in their “strategic” arsenals, or those weapons aimed at each other’s homeland. Then, with the collapse of the Soviet Union, MAD was assumed to hold sway in the US-Russia nuclear competition—largely eliminating fears of a deliberate nuclear strike. Future wars, it was largely assumed, would be of a limited nature, fought entirely with non-nuclear, conventional weapons.

This was the outlook embodied in President Obama’s stance on nuclear weapons. The United States, he declared in Prague in an April 2009 address, “will reduce the role of nuclear weapons in our national security strategy.” Recognizing, however, that the threat of armed conflict would not disappear, he called for improvements in US conventional capabilities, allowing punishing attacks on potential adversaries without reliance on atomic munitions. This stance was embodied in the administration’s Nuclear Posture Review Report (NPR) of April 2010. “As the role of nuclear weapons is reduced in U.S. national security strategy,” the 2010 NPR states, “non-nuclear elements will take on a greater share of the deterrence burden.” In consonance with this policy, the Obama administration devoted ever-increasing sums on the acquisition of advanced conventional weapons, including stealth fighters, nuclear submarines, and precision-guided missiles.

The United States, with its huge military-industrial complex and an ever-increasing defense budget, has experienced no difficulty in deploying large numbers of such weapons. But no other country (with the possible exception of China) is in a position to match the US in this regard, and so potential rivals like Russia are faced with a harsh strategic dilemma: how do you avert defeat in a conventional conflict with better-equipped US forces?

The Russians under Putin have done their best to match the Americans in the development of advanced missiles and the like, some of which have been employed in Ukraine. But Russian strategists have suggested that their country will always be at a disadvantage in a conventional fight with the United States, and so it may be necessary to employ so-called “tactical” or “non-strategic” nuclear weapons (that is, munitions intended for battlefield use rather than massive retaliation) to pummel enemy forces and compel their surrender. To what degree this approach—sometimes termed “escalate to de-escalate” by Western analysts—has actually been embodied in formal Russian military doctrine (as distinct from its being bandied about in the open literature) is unknown. However, US military officials claim that it has been thus incorporated and that Moscow has sought to implement the approach by modernizing its arsenal of non-strategic nuclear munitions (said to number about 1,900) and simulating their use in elaborate war games.

This, in fact, was the basis upon which the Trump administration called for an expansion of America’s own array of tactical nuclear weapons and for their potential use in response to any such nuclear usage by Russia. Although the Pentagon has long maintained a stockpile of 100 or so 100 B-61 tactical nuclear bombs in Europe for use in a possible war with Russia, the Nuclear Posture Review issued by President Trump in 2018 contends that these may not be enough to dissuade Russia from pursuing an “escalate to de-escalate” strategy: “Moscow threatens and exercises limited nuclear first use, suggesting a mistaken expectation that coercive nuclear threats or limited first use could paralyze the United States and NATO and thereby end a conflict on terms favorable to Russia.”

To ensure that Moscow entertains no illusions about NATO’s determination to overcome any conceivable Russian threat, the Trump NPR called for the acquisition of several new types of tactical munitions, including a “low-yield” warhead for the Trident submarine–launched ballistic missile, the W-76-2, and a new nuclear-armed sea-launched cruise missile (SLCM-N). “Expanding flexible U.S. nuclear options now, to include low-yield options, is important for the preservation of credible deterrence against regional aggression,” the 2018 NPR avowed. (A classified number of W-76-2 warheads have been deployed on Trident submarines since 2019; funding has been requested for development of the SLCM-N, but none have yet been deployed.) Like the Obama NPR before it, moreover, the 2018 NPR authorizes the use of nuclear weapons to overcome a massive non-nuclear assault by an adversary, much as is the case for Russian nuclear doctrine.

Possible Nuclear Scenarios

How, and under what circumstances Russia or the United States might employ their non-strategic nuclear munitions in a European conflict is a closely guarded secret on both sides, and probably could never be determined in advance anyway. But some Western analysts have suggested that Putin might order the use of one or more such weapons if he believed Russian forces in Ukraine were at risk of suffering major losses. Such an eventuality, it is claimed, would represent a massive blow to Putin’s prestige at home and possibly threaten his political survival—making him “desperate” to achieve a breakthrough by any means necessary, including nuclear weapons use.

“Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they’ve faced so far, militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low-yield nuclear weapons,” said CIA Director William J. Burns during a question-and-answer session following a speech he delivered at the Georgia Institute of Technology on April 14.

Some analysts have also suggested that Russia might, in desperation, seek to block the flood of arms from NATO to Ukrainian forces by detonating a tactical nuclear weapon in far western Ukraine, along the road and rail corridors used to ship the weapons from Poland to frontline forces. Such a strike would be consistent with Putin’s warnings about “unpredictable consequences” should the United States and NATO increase the flow of advanced weapons to the Ukrainians.

Whether Putin would actually consider such an action in either case is doubtful, given the international vilification he would face. Even China—until now unwilling to denounce Russia for the invasion—would be obliged to abandon Moscow under such circumstances. But having issued a series of nuclear threats, Putin might feel compelled to act on them, lest his future ability to threaten nuclear retribution (and so intimidate potential adversaries) disappear.

Nor is this the only way in which the Ukraine war could spark a nuclear exchange. Until now, President Biden has reportedly sought to prevent a direct clash between the US/NATO and Russian forces, fearing the escalatory consequences of such a confrontation. But as NATO provides increasingly sophisticated arms to the Ukrainians, thereby threatening the success of the Russian offensive in the east, the likelihood is growing that such a clash could occur. Russia has already fired missiles at Ukrainian logistical bases near the Polish border, and NATO and Russian planes regularly buzz each other in the airspace above the Polish-Ukrainian border. Should Russia bomb NATO facilities on the Polish side of the border, or those daily encounters result in planes being shot down, the United States and NATO could quickly find themselves in a shooting war with Russia—and from there, one thing could lead to another until conventional forces on both sides were engaged in full-scale combat. At that point, the use of nuclear weapons to stave off catastrophic defeat would be consistent with the military doctrines of both sides.

We may be lucky, and the war in Ukraine will end without any of these scenarios coming to fruition. At present, however, we can have no assurance that this will prove to be the case, as the US and NATO step up their arms aid to the Ukrainians and Putin becomes more fearful of an embarrassing deadlock in Ukraine. And even if we escape nuclear weapons use this time around, we can be certain that every future encounter between the US and Russia will entail a high risk of such usage. The fact that Putin has normalized the use of nuclear threats in a major-power crisis also means that the specter of Armageddon will hover over every other such engagement—including, say, a future US-China clash over Taiwan.

Survival, in this New Nuclear Era, cannot be entrusted to luck, or to the whims of nuclear-state leaders like Vladimir Putin. It can only be ensured when nuclear weapons are abolished and, until then, if measures are put in place to prevent their accidental, inadvertent, or frivolous use. This will occur only in response to a massive worldwide anti-nuclear movement, akin to the global mobilization for climate change action. We can see the initial stirrings of such a movement today, with the work of groups like Beyond the Bomb and Back from the Brink, but it will take a much larger effort to overcome the elevated risk of nuclear annihilation.