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Putin’s Brutal War Shows the Dilemmas of Nuclear Deterrence

Powerful threats could too easily become real disasters.

By , a senior fellow at the Royal United Services Institute.
Firefighters sit amid debris in the area of a research institute, part of Ukraine's National Academy of Sciences, after a strike by drones, in northwestern Kyiv.
Firefighters sit amid debris in the area of a research institute, part of Ukraine's National Academy of Sciences, after a strike by drones, in northwestern Kyiv.
Firefighters sit amid debris in the area of a research institute, part of Ukraine's National Academy of Sciences, after a strike by drones, in northwestern Kyiv, on March 22. Fadel Senna/AFP via Getty Images

Putin’s War

Even without having been used yet, nuclear weapons have shaped the war in Ukraine—and its outcomes will shape our views of nuclear weapons for years to come. The power of nuclear deterrence has added to the destruction that Russia has inflicted on Ukraine while reducing the chances that conflict will spread into NATO territory.

For now, Russia and NATO are effectively deterring each other—to some degree—while Ukraine is caught in between. NATO countries are acting more cautiously than they would be if Russia were not nuclear-armed. It’s tricky to measure this effect, or to separate the influence of nuclear weapons from fear of a wider conventional war, but it’s present, nonetheless. Yet deterrence is neither as stable as some strategists insist nor as easy to escape as some disarmament advocates hope.

Nuclear weapons have not deterred NATO countries from openly and heavily arming Ukraine or from imposing harsh sanctions on Russia and furthering its international isolation. As Russia’s violence against Ukraine continues to increase, so will NATO’s support to Ukraine, as well as public pressure for direct intervention. Some Western voices are already arguing that NATO has allowed itself to be too cowed by Russian nuclear threats, not just in ruling out direct military action but by avoiding some showier measures, such as the proposed transfer of Polish MiG-29 aircraft to Ukraine.

Even without having been used yet, nuclear weapons have shaped the war in Ukraine—and its outcomes will shape our views of nuclear weapons for years to come. The power of nuclear deterrence has added to the destruction that Russia has inflicted on Ukraine while reducing the chances that conflict will spread into NATO territory.

For now, Russia and NATO are effectively deterring each other—to some degree—while Ukraine is caught in between. NATO countries are acting more cautiously than they would be if Russia were not nuclear-armed. It’s tricky to measure this effect, or to separate the influence of nuclear weapons from fear of a wider conventional war, but it’s present, nonetheless. Yet deterrence is neither as stable as some strategists insist nor as easy to escape as some disarmament advocates hope.

Nuclear weapons have not deterred NATO countries from openly and heavily arming Ukraine or from imposing harsh sanctions on Russia and furthering its international isolation. As Russia’s violence against Ukraine continues to increase, so will NATO’s support to Ukraine, as well as public pressure for direct intervention. Some Western voices are already arguing that NATO has allowed itself to be too cowed by Russian nuclear threats, not just in ruling out direct military action but by avoiding some showier measures, such as the proposed transfer of Polish MiG-29 aircraft to Ukraine.

Wherever the war goes from here, it’s clear that nuclear deterrence is not automatic or inherent to the mere possession of nuclear weapons. It does not exist unless the other side believes there is a real, credible chance you would use the weapon. And credibility, as we can see in this war, depends on the stakes at play and the appetite for risk of the actors involved.

Russian President Vladimir Putin’s nuclear bluster carries at least some credibility because Ukraine is a high-stakes game for him and because he is obviously willing to endure severe costs to win. NATO countries’ stakes in the conflict—and particularly those of the United States—appear lower than Russia’s. At least for now, most NATO leaders have a lower pain threshold than the Russian president.

Yet deterrence is dynamic, not static. The progress of the war changes the stakes. If the Russian military’s apparent struggles continue, Putin could conceivably find himself losing a war on Russia’s borders while facing challenges to his rule at home via economic chaos and public protest. This could look to him like the kind of existential threat that would make the risks of nuclear use worth running, especially because Ukraine itself cannot threaten retaliation in kind to a nuclear attack on its soil. At a minimum, there may be more acute nuclear threats to come, which could move beyond rhetoric to include real changes in the alert status or deployment of Russia’s nuclear forces.

In recent years, there has been a debate among experts about whether Russia’s doctrine provides for using a limited nuclear strike to end a conventional war on favorable terms. Some Western strategists used worries about such a strike to argue for new limited nuclear options, and the United States duly developed a new low-yield warhead variant for its Trident missiles. Many scholars of Russian strategy were skeptical, believing that Americans had talked themselves into identifying a so-called “escalate to de-escalate” ploy that might have reflected Russian thinking some years ago but which was not supported by current evidence. Yet the question of whether such a strike had a place in formal Russian doctrine was always less important than what a leader might do in desperate circumstances. A stronger argument not to worry about “escalate to de-escalate” was that it would be reckless and counterproductive for Russia.

But Putin’s war has already been an act of reckless self-harm, wrecking Russia’s economy and international standing, weakening his political position, and exposing the Russian army’s weaknesses, making total confidence harder to sustain. Putin might also end up convincing himself that there are ways of using nuclear weapons that could trigger some kind of military response from NATO but might not automatically invite his destruction, such as a so-called demonstration shot designed to avoid substantial casualties and minimize fallout.

NATO, for its part, could find itself witnessing such slaughter on its borders—potentially even including the use of chemical weapons—that Russia could look like a threat that had to be confronted with force sooner rather than later. If so, NATO countries might be more willing to run the risk of escalation.

Even if blunt instruments such as a no-fly zone over the whole of Ukraine have so far been rejected, some observers think NATO should be preparing options to intervene if Russia’s violence escalates. Their assumption is that the United States and NATO’s ability to threaten devastating retaliation, potentially including nuclear retaliation, should be enough to deter Putin from using nuclear weapons against a NATO member and that the risk of conventional escalation would be acceptable given the costs of inaction.

The first conclusion to draw from all this is that nuclear deterrence is an inherently risky way of managing relations between great powers. Because deterrence is neither automatic nor static, there is no way to reap its prime benefit—discouraging war between nuclear-armed states—without some real chance of nuclear weapons being used, even if the probability is low. Unusable weapons cannot deter, and the risk of nuclear use will be present during any crisis of the sort currently seen in Ukraine.

What’s more, the strong normative taboo against nuclear weapons means that the most reckless party to a conflict can extract the most value from playing with nuclear risk. In this case, it is clearly Russia. Nuclear brinksmanship may become a feature of Europe’s security landscape in a way that its current generation of leaders have not experienced firsthand. These risks are compounded by the possibility of inadvertent escalation. With tensions high and Russia fighting in close proximity to NATO forces, a mistake or misjudgment could be the spark for a wider war.

Yet despite its dangers, moving away from nuclear deterrence will be very difficult. Unless the war ends in Russian defeat and regime change, Russia’s leadership will probably reckon it has benefited greatly from possessing nuclear weapons and will be even less inclined to disarm.

Meanwhile, the rest of the world is watching Russia’s brutal aggression, conducted under the cover of nuclear threats and inflicted on a non-nuclear country that, unlike NATO members, does not enjoy the United States’ nuclear backing. This has awakened a sense of existential threat in Europe and is likely to strengthen support for nuclear weapons where they already exist. It has already ensured, for example, an accelerated German decision to procure F-35 fighters to replace the aircraft currently equipped with NATO nuclear bombs.

So, as things stand right now, Russia’s invasion may have killed off for a generation or more the idea of an orderly, multilateral process of nuclear disarmament. That process was imagined as a managed series of steps, starting with deep reductions to the nuclear stockpiles of Russia and the United States and then drawing in the other nuclear-armed states, including China. It depended on the belief that nuclear weapons could be gradually moved to the background of world affairs. None of that seems likely today.

Two drastic war outcomes—the use of nuclear weapons or Putin’s removal from power—could change this picture and even perhaps open up more sudden and disorderly paths to disarmament.

A large-scale nuclear exchange would be a global catastrophe and remains unlikely. Yet if nuclear weapons were used in a limited way, there would be plausible pathways to further escalation. Indeed, nuclear deterrence relies on at least some fear of uncontrolled escalation in order to work. No risk, no deterrence.

Nuclear use that did stay limited would still be a historic turning point, its meaning defined by the consequences imposed on Russia. If Russia were to use a small number of nuclear weapons with impunity and achieve concrete benefits, then, in addition to immediate humanitarian consequences, we would enter a dreadful new nuclear era. As well as killing off hopes for disarmament, Russian success could entice nuclear possessors to develop a broader range of limited options and even make use more likely elsewhere.

On other hand, if the limited use of nuclear weapons led to catastrophic consequences for Russia—even if this did not involve nuclear retaliation—then demands for disarmament might be back on the table. If the result were Putin’s fall from power, nuclear blackmail would be seen as a fruitless gamble. And the first nuclear detonation in anger since 1945 might make politicians and publics reconsider whether the benefits of deterrence could ever outweigh the risks of this happening again.

These extreme scenarios are, for now, only speculation. In the meantime, we will have to relearn what it means to live with nuclear risk. Nuclear deterrence is certainly a dangerous way to run the world. The outcome of this terrible war may determine whether we are stuck with it for good.

Matthew Harries is a senior fellow at the Royal United Services Institute and former specialist for the U.K. House of Commons Foreign Affairs Committee.

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