During the first week of Russia’s invasion of Ukraine, Russian leaders repeatedly raised the prospect of a nuclear response should the United States or its NATO partners intervene in the war. Russian President Vladimir Putin concluded his speech announcing war in Ukraine by warning that “anyone who tries to interfere with us … must know that Russia’s response will be immediate and will lead you to such consequences as you have never before experienced in your history.” He subsequently emphasized Russia’s “advantages in a number of the latest types of nuclear weapons” while ordering Russian strategic nuclear forces on alert. Russian Foreign Minister Sergey Lavrov returned to this theme a few days later, noting that a third world war would be a nuclear war and urging Western leaders to consider what a “real war” with Russia would entail. The message was crystal clear: nuclear escalation is possible should the United States or its NATO partners intervene in Russia’s war against Ukraine.

Observers have expressed shock at the notion of a return to Cold War nuclear brinksmanship. The U.S. government even tried to reassure Moscow by postponing an intercontinental ballistic missile test planned for early March. These steps are clearly for the best; no one wants a nuclear exchange. Yet the heavy focus on nuclear escalation is obscuring an equally important problem: the risk of conventional escalation—that is to say, a non-nuclear NATO-Russia war. The West and Russia may now be entering into the terminal stages of an insecurity spiral—a series of mutually destabilizing choices—which could end in tragedy, producing a larger European conflagration even if it doesn’t go nuclear.

Indeed, the coming weeks are likely to be more perilous. The United States should be especially attuned to the risks of escalation as the next phase of conflict begins, and should double down on finding ways to end the conflict in Ukraine when a window of opportunity presents itself. This may involve difficult and unpleasant choices, such as lifting some of the worst sanctions on Russia in exchange for an end to hostilities. It will, nonetheless, be more effective at averting an even worse catastrophe than any of the other available options.

Tit for tat

In the parlance of security studies, an insecurity spiral ensues when the choices one country makes to advance its interests end up imperiling the interests of another country, which responds in turn. The result is a potentially vicious cycle of unintended escalation, something that’s happened many times before. For example, Germany’s attempt at the turn of the twentieth century to build a world-class navy threatened the naval power on which the United Kingdom depended; in response, London began to bulk up its own navy. Germany responded in kind, and soon, the scene was set for World War I. The origins of the Cold War between the United States and the Soviet Union share a similar genesis, as both sides sought influence throughout the world and engaged in an arms race. In each case, a tit-for-tat spiral drove states toward conflict.

Today, the United States and Russia have already taken steps to shore up their real or perceived sense of insecurity, spurring the other side to do the same. As the scholars William Wohlforth and Andrey Sushentsov have argued, the United States and Russia have been engaged in a slow-motion spiral throughout the post-Cold War era as each sought to refashion European security to its liking and tried to limit the other side’s inevitable response. Recent events highlight the trend: the 2008 Bucharest summit, at which NATO pledged to bring Ukraine and Georgia into the alliance, was followed by Russia’s 2008 invasion of Georgia. A 2007 dispute over the Bush administration’s plans to base missile defense in Poland and the Czech Republic was followed by Russian violations of related arms-control agreements. In 2014, the EU’s offer to Ukraine of an association agreement precipitated the Maidan revolution in Kiev, heightening Russian fears of Ukrainian NATO membership and prompting the Russian seizure of Crimea that year.

Russia’s invasion of Ukraine, however, has dangerously upped the ante and accelerated the spiral’s pace. In response to Moscow’s wanton and illegitimate aggression, the United States, NATO, and EU member states have sent Ukraine significant quantities of lethal weapons, placed draconian sanctions on Russia’s economy, and launched a long-term military buildup. Currently, Moscow sees the United States and its partners threatening to make Ukraine into a de facto ally—a situation Moscow’s own aggression helped cause—whereas the United States sees Moscow threatening the core principles undergirding peace in Europe.
For sure, Russia has been dramatically less restrained in military terms than the West —shelling Ukrainian cities, for instance—while the Biden administration has gone out of its way to signal its unwillingness to directly intervene in the conflict. Based on this, one might infer that one side is willing to escalate and another isn’t. Still, spirals are defined by their tragic nature: even states that might not want to directly confront one another end up competing and risking war. As Russia’s invasion continues, Western arms flood into Ukraine and sanctions threaten to collapse the Russian economy. Each side appears committed to ratcheting up the pressure further. It may take just a single spark to ignite a broader conflagration.

The widening gyre

For obvious reasons, much of the concern about escalation has focused on the nuclear question. Putin’s announcement that Russian strategic nuclear forces would be raised to a higher alert status was a clear attempt to deter direct Western military action by raising the stakes. But although policymakers are right to take nuclear escalation seriously, they should not discount the risks of conventional war between NATO and Russia. After all, low-level conventional conflicts between nuclear powers have occurred elsewhere, including clashes between China and the Soviet Union in the 1960s and in the 1999 Kargil war between India and Pakistan.

Scholars have developed a theory to explain why such conflicts happen: the stability-instability paradox, in which states, stalemated in the nuclear realm, might be more willing to escalate in conventional terms. There are multiple paths through which such an escalation to a broader war might happen today. One scenario stems from the economic war the West has launched against Russia in the last week. By preventing the Kremlin from using its foreign exchange reserves and applying export controls to stop Russia from importing high-tech goods, Washington and its allies have entered into uncharted territory: such sanctions have never been used against a major global economy such as Russia. Even in a few short days, the effect of these measures has been widely felt: the ruble crashed, Russian citizens lined up at banks to withdraw their savings, the Russian government imposed capital controls, and Western companies such as BP and Ikea rapidly exited the Russian market.

It is hard to think of historical parallels to this sudden isolation of a major economy, and the few comparable historical cases—Italy in the 1930s, Japan in the 1940s—do not bode well. Indeed, if the economic damage in Russia becomes severe enough, Putin may decide that it is worth retaliating through nonmilitary means such as cyberattacks. He may decide things are bad enough that it is worth forgoing energy revenues and shut down some gas pipelines to Europe, which would send energy prices soaring. Russia would presumably hope to use these steps to gain leverage over Western policy, but they could easily backfire: cyberattacks could trigger consultations under Article 5 of NATO’s founding treaty, which states that an attack against one member state will be considered an attack against them all. This could result in retaliatory cyberattacks on Russia and continue from there. One might hope policymakers find off-ramps at that stage, but there are no guarantees.

The United States sees Moscow threatening the core principles undergirding peace in Europe.

There is also a serious risk that the conflict in Ukraine might spill over its borders. Europe is engaged in a rapid period of rearmament, with dramatically shifting security conditions on the ground. Russia’s actions in Ukraine have obscured its de facto military annexation of Belarus, and US forces have poured into the region to reinforce NATO’s eastern member states. This has heightened tensions and made accidental confrontation between the sides more likely.

Amid Russia’s attack on Ukraine, for example, four Russian planes violated Swedish airspace. Though a frequent occurrence during peacetime, it is highly dangerous during a shooting war and could easily draw antiaircraft fire. The problem would be worse if Russian planes accidentally violated the airspace of a NATO member state bordering the conflict. Another possibility: since the start of the conflict, arms have flowed into Ukraine to bolster its defense, at first by air but more recently on land through transfers from the NATO states bordering the war zone. If the war continues, Russia might decide to shut down these transfers by, for example, attacking supply lines leading from the transfer points; such efforts might inadvertently kill or harm NATO personnel. Again, an escalating spiral could take hold. These problems will only become more pressing if Russia continues to take territory inside Ukraine and the land routes for resupply become more limited.

Finally, there is always the risk of freelancing by regional allies, which might draw Russia and the rest of NATO into direct conflict. Thus far, unity within the alliance has been impressive, but the NATO member states closest to Russia—particularly Poland and the three Baltic states (Estonia, Latvia, and Lithuania)—are the ones that have been among the most ardent and active proponents of arming Ukraine. This has included questionable announcements such as an unexpected offer—since walked back—to give Ukraine surplus European fighter jets. If the Russians seize Kyiv or overthrow the Ukrainian government, these states will likely be strong proponents of arming and supporting an insurgency inside Ukraine. What will the United States do if Russia bombs a Ukrainian camp or resupply mission on, for example, Polish territory? What if Lithuanian troops—perhaps operating on their own or having misread a map—are killed while delivering arms to Ukrainian forces? As seen in conflicts from Colombia to Syria, this kind of support risks blurring the lines between combatants and noncombatants, dramatically increasing the risks of a broader war.

Staying on the sidelines

It is widely assumed that a conventional great power war is impossible in the nuclear era. The logic is clear: the stakes are simply too high for nuclear-armed states to make that kind of decision. Yet insecurity spirals have their own logic, and Washington should heed the lessons of history.

Although the Biden administration has been relatively careful and judicious in its approach to arming Ukraine, it may be rapidly approaching a more perilous period of this conflict. Ukrainian defenses have operated better than anticipated. Still, the odds are on Russia’s side, and Russian forces will likely seize more Ukrainian cities and inflict more harm on Ukrainian civilians, thus increasing moral outrage at Russia’s actions. Pressure is likely to mount for Western governments to offer additional assistance to Ukraine, particularly if an insurgency erupts in Russian-occupied areas.

The Biden administration should be extremely wary about responding to such pressure. In particular, arming and backing an insurgency would blur the line between being a supporting actor and being a co-combatant. The United States must also be prepared to restrain its allies. For example, it may be tempting for the countries closest to the conflict to consider unilateral steps such as supporting an insurgency or offering Ukrainian fighters safe haven on their territory. Nevertheless, it would not be out of line to make clear that the United States might interpret Article 5 commitments loosely in such instances, meaning that should Russia retaliate, the United States might not be obligated to respond with military force. Amid the present spiral, Biden and his team must determine where the United States’ own limits fall and focus on remaining well within them.

The most effective way to curtail the risks of escalation in Europe is to end the conflict in Ukraine. This will be difficult, perhaps impossible, to do in the near term given the brutality of Russian behavior, the irreconcilable demands of each side, and the West’s understandable desire to support Ukraine. At some point, however, the United States may need to use its leverage with all parties—for example, the prospect of lifting the most draconian sanctions on Russia or reducing its military aid for Ukraine—to bring about a ceasefire or settlement. Such a move would amount to a sea change in US policy thus far. But because the alternative may be to get pulled into a direct military engagement with Russia, hardheaded consideration of US interests may require a course adjustment. Ultimately, the only thing more tragic than the present war would be an even bigger, bloodier one.

EMMA ASHFORD is a Senior Fellow in the New American Engagement Initiative at the Atlantic Council and an Adjunct Assistant Professor at Georgetown University.  

JOSHUA SHIFRINSON is Associate Professor of International Relations at Boston University, a Fellow with the Woodrow Wilson International Center for Scholars, and the author of Rising Titans, Falling Giants: How Great Powers Exploit Power Shifts.