How the United States and NATO can deal with Russian nuclear coercion in Ukraine

It has been more than a year since the start of Russia’s full-scale invasion of Ukraine. Russia’s unprovoked war of aggression unleashed the biggest crisis in European and global security since World War II. And there is still no end in sight. Russian President Vladimir Putin’s war of choice has also brought the world closer to the nuclear brink than at any time since the Cuban Missile Crisis, and it has put in doubt the future of East-West arms control negotiations and international efforts to control the spread of nuclear weapons.

A lot is on the line in this conflict, which goes beyond Ukraine’s survival as an independent state. Russia has challenged many of the fundamental principles of the international order on which European and global security have long been based—principles like respect for the sovereignty and territorial integrity of states, no changing of borders by force, and freedom for nations to choose their security arrangements, including treaties of alliance.

In threatening to use nuclear weapons to achieve his objectives, Putin has displayed a disturbing readiness to break the taboo on nuclear use that has prevailed since 1945, eroding strategic stability and undermining the nuclear nonproliferation regime. Nuclear risks could be exacerbated by Russia’s latest decisions to suspend compliance with the New Strategic Arms Reduction Treaty (New START) and to deploy nuclear weapons in Belarus.

While the United States and its allies must manage the risks of nuclear escalation carefully, defeating Putin, restoring Ukrainian sovereignty, and reinforcing the rules-based order must be our priorities.

Putin’s fear. Despite many setbacks on the battlefield and multiple miscalculations by Putin, Moscow’s war aims have not changed since the start of the war on February 24, 2022. It still seeks to subjugate Ukraine to Russian hegemony, to annex territories that Putin views as historically Russian lands, and to erase Ukrainian national identity altogether on the grounds that Ukrainians are really just Russians who have been led astray by the evil West. Putin wants to bring Europe back to the days of spheres of influence and “might makes right,” forcing Kyiv to renounce security ties with NATO. He has shown no sign of readiness to negotiate an end to the conflict on terms other than Ukraine’s complete capitulation and acceptance of the “new territorial realities,” namely, Moscow’s purported annexation of Crimea and four other Ukrainian provinces.

At the root of the crisis is Putin’s fear of Ukrainian democracy, which he sees as a dagger pointed at the heart of Russia and his imperial ambitions. For Putin, the success of democracy in Ukraine would set a dangerous example to the Russian people that would ultimately undermine the authoritarian system Putin has built since taking power 23 years ago.

If Russia succeeds in achieving its objectives, even partially, it will damage fundamental US and NATO interests. It will increase the Russian military threat to NATO and encourage other despots with revisionist ambitions to follow Putin’s example, including his resort to nuclear threats. One most dangerous, yet plausible, scenario is an emboldened China, with expanding nuclear and conventional arsenals, seeking to subjugate Taiwan by force.

Putin himself has been clear that his own ambitions extend beyond Ukraine. If not stopped there, Putin could use force against other former Soviet countries that Putin considers as historically belonging to the Russian Empire. These include NATO members, such as Estonia, Latvia, and Lithuania, that are covered by the alliance’s Article 5 guarantee and the US nuclear umbrella.

Self-restraint won’t work. Allies need to provide sufficient conventional weapons to enable Kyiv to repel Russia’s ongoing offensive in eastern Ukraine and support a Ukrainian counteroffensive that can recover more occupied territory. By helping Ukraine gain the upper hand on the battlefield in the coming months, allies can strengthen its hand at the negotiating table and increase the chances of achieving a just peace.

While thus far Russia has not followed through on its threats to use nuclear weapons, its nuclear saber-rattling has been effective in one important way: constraining the types and quantity of conventional weapons that the United States and its allies have been willing to provide to Ukraine. As President Biden has said many times, the United States and its allies are committed to supporting Ukraine “for as long as it takes,” but in a way that avoids triggering World War III.

The declared rationale for this policy is to prevent or discourage a Russian escalation of the conflict, especially to the nuclear level. In practice, however, self-restraint has often invited more Russian escalation—such as the massive attacks in recent months on Ukrainian power grids and other critical civilian infrastructure. The desire to discourage Russian escalation has led the United States to deny longer-range missiles like the Army Tactical Missile System (ATACMS) and advanced drones that could eliminate many of the Russian weapons carrying out many of the infrastructure attacks.

In effect, the United States and its allies have given Russia a sanctuary in occupied Crimea and in neighboring regions of Russia from which to launch its brutal attacks on Ukrainian civilians. Putin wouldn’t be wrong in concluding that nuclear coercion works.

The consequences of this self-restraint for Ukraine’s war plans could be dire, however.

Ukrainian armed forces made extraordinary gains in the fall of 2022, thanks to the delivery of sophisticated long-range rocket and artillery systems from the United States and other allies, including the much-publicized High Mobility Artillery Rocket System (HIMARS). This enabled them to destroy dozens of Russian ammunition depots and command posts behind the front lines, creating the conditions for Ukraine’s successful counteroffensives in Kherson and Kharkiv.

Most experts agree that further Ukrainian victories are possible if they receive sufficient support for their ongoing counteroffensive, which started in the late spring and may extend well into the summer or fall. But there may not be enough HIMARS or other heavy weapons in the pipeline for Ukraine to consolidate its gains and retake more territory in the coming months. While allies have belatedly agreed to provide modern tanks and other armored capabilities, only a few battalions of tanks are likely to arrive this year. Ukraine also needs more air defense systems to cope with the threat posed by Russian cruise missiles and Iranian drones.

While recent decisions to accelerate production will help, US and allied defense ministries may be too slow, and policymakers too cautious, to ensure that Ukraine gets the advanced capabilities it needs, and quickly enough, to inflict a decisive defeat on the Russians this year. Meanwhile, some senior officials in the Biden administration have been openly urging the Ukrainians to quit while they are ahead and engage in negotiations with Russia—even though talks right now would be used by the Russians to freeze the battle lines and hold onto illegally occupied Ukrainian lands.

The Biden administration has reiterated that it is up to the Ukrainians to decide when and how to negotiate. But mixed signals from Washington (and from some European capitals) may convince Putin that time is still on his side if he can steer things toward a stalemate. He may still be confident that the Ukrainians will ultimately become exhausted by the Russians’ relentless and indiscriminate attacks on civilian infrastructure and that Western unity and public support will continue to erode.

Firm but calibrated support. The next few months will be crucial to restoring momentum to the Ukrainian campaign. The United States and its allies need to commit themselves unequivocally to the goal of Ukrainian victory and act accordingly in their support for the Ukrainian military. Allies need to calibrate what weapons they provide to avoid escalation, but they should not let themselves be intimidated or self-deterred by Russia’s saber-rattling.

The nuclear risks must be kept in perspective. Putin has brandished nuclear threats from the moment he launched his re-invasion of Ukraine last year. He reinforced those threats in September, after Russia’s defeat at the hands of the Ukrainian counteroffensive in Kharkiv. With his subsequent move—holding fake referenda as the basis for annexing four Ukrainian provinces in the South—Putin appeared to be doubling down on his nuclear threats. It sounded as though he was daring the Ukrainians and their Western backers to risk nuclear retaliation if they attempted to retake territory that was now purportedly an integral part of Russia (even though it was only partially under Russian control).

But over the succeeding weeks, Putin pulled back from the brink. In his speech to the Valdai Discussion Club in late October, he claimed that he had never considered the use of nuclear weapons and declared that using nukes would be “pointless” in military terms. This climbdown may have been a response to pressure from China, India, and other partners that were becoming increasingly alarmed by Putin’s cavalier nuclear threats. Putin may have been deterred even more by US warnings of “catastrophic consequences” for any Russian use of nuclear weapons.

Although the immediate risk of nuclear use may have receded, there are no grounds for complacency. Putin continues to escalate the conflict in non-nuclear domains, with the destruction of civilian infrastructure and the general terrorization of the Ukrainian population. The March 14 shootdown of a US reconnaissance drone over the Black Sea could signify a new willingness to challenge allied military support for Kyiv. In recent weeks, Putin has threatened to dismantle the remaining constraints on strategic nuclear forces by suspending New START and announcing plans to deploy tactical nuclear weapons in Belarus. Both moves are clearly intended to raise anxiety among NATO governments and publics.

Putin may renew his direct threats to use nuclear weapons if Russian forces suffer major new setbacks on the ground, and especially if Ukrainian armed forces mount a serious threat to Russia’s hold on Crimea, which Putin views as central to his political legacy as the in-gatherer of historically Russian lands. Losing control over Crimea could bring Putin under intense pressure from hardliners to use nuclear weapons to stave off defeat and punish the Ukrainians and their Western backers. One recent example of hardline views can be found here.

But even in that case, it will always be a lot easier for Putin to threaten nuclear escalation than to carry it out in practice. The effects on Russian troops and civilians of even a low-yield nuclear strike or “demonstration” shot could be quite severe and unpredictable, given the vagaries of the weather.

Although Putin was uncharacteristically reckless in launching this war of aggression, he is unlikely to want to risk the “catastrophic consequences” promised by the United States, even if his back is up against the wall. Those consequences may primarily involve massive conventional strikes on Russian forces and military infrastructure in Ukraine; but the United States has not ruled out a limited nuclear response in kind if Russia breaks the nuclear taboo that has been in place since 1945.

Moreover, for Putin to violate the nuclear taboo would only increase Russia’s political isolation and potentially elicit opposition from Russian miliary commanders that could threaten Putin’s grip on power.

Using nuclear weapons would increase the likelihood that the United States and NATO would be drawn directly into the conflict, which Putin has been keen to avoid from the very outset of the war. It could prompt calls within NATO to expand tactical nuclear weapon deployments in Europe beyond the limited steps called for in the Biden administration’s Nuclear Posture Review (NPR). A new NPR may be needed in any case to redress the imbalance between US and Russian non-strategic capabilities that will be exacerbated by deployments in Belarus, and to counter China’s looming nuclear buildup.

Whatever one’s assessment of the probability of nuclear use by Russia, it will be essential to strengthen deterrence by making clear to the Russians that they would pay a very heavy price—in terms of a swift and decisive military response, a ratcheting up of economic sanctions, and further political isolation of Russia—if they break the nuclear taboo.

And above all, Moscow should understand that the United States and its allies will not be deterred from continuing to arm and train Ukrainian armed forces fighting to restore their country’s independence, sovereignty, and territorial integrity.

Standing firm in helping Ukraine regain its territory is the best way to persuade the Russian officials that their best course of action is to end the war, withdraw their forces from Ukraine, and negotiate a political settlement that restores Ukraine’s sovereignty within its internationally recognized borders, holds Russia accountable for war crimes, and provides guarantees that Russia will not invade a third time.

Ripple effect. Other countries, including North Korea and Iran, will be watching to see how firmly the West stands up against Russian nuclear coercion. Both may see the US preoccupation with the Ukraine crisis as an opportunity to advance their nuclear ambitions.

Indeed, in the case of North Korea, the year of 2022 saw a major spike in tests of intercontinental and shorter-range ballistic missiles aimed at intimidating the United States and South Korea from conducting longstanding joint military exercises on the Korean peninsula. Pyongyang is reportedly preparing for another nuclear weapons test, has renounced its previous commitment to denuclearization even as a long-term goal, and has spurned US offers of dialogue without preconditions on lowering tensions. The North Koreans may be planning to provide conventional weapons and munitions to Russia in return for economic aid and sanctions relief, which will only make Pyongyang even more recalcitrant about negotiating reductions in its nuclear weapons program and more provocative in carrying out more nuclear and missile tests.

For its part, Iran has stepped up to the threshold of becoming a nuclear weapon country by enriching uranium to close to weapons grade. This seriously reduces the value of reviving the Joint Comprehensive Plan of Action (JCPOA), even if such a revival were politically possible. With Russia increasingly dependent on imported Iranian drones in its war against Ukraine, Moscow may decline to do anything to convince Tehran to comply with its JCPOA obligations. The United States and its allies will need to consider additional forms of pressure on Tehran to discourage a decision to break out of the deal, which may be the only way to head off unilateral Israeli military action to destroy or damage the Iranian program.

Editor’s note: The statements made and views expressed in this article are solely the responsibility of the author. This article is a product of a Perry World House workshop on “The Future of Nuclear Weapons, Statecraft, and Deterrence after Ukraine,” which took place on April 4, 2023. This workshop was made possible in part by a grant from Carnegie Corporation of New York.