As Ukrainian forces launch attacks inside Russia, how will Russia respond? Even before the August 2024 incursions, Russian President Vladimir Putin’s threats to use nuclear weapons in the conflict left both the American public and policymakers deeply concerned. What potential events – if any – do experts think might lead Putin to use nuclear weapons against Ukraine?
To better understand these questions, the TRIP (Teaching, Research, and International Policy) survey asked international relations (IR) scholars in June and July 2024 to assess the likelihood of nuclear escalation in the war in Ukraine, under several different scenarios. Over 700 scholars responded to these questions. Most (74%) thought there was a 20% or less chance that Russia would use nuclear weapons in Ukraine in the next two years. However, respondents identified two scenarios in which the probability of a Russian nuclear strike meaningfully increased: if Ukrainian forces attacked Russian nuclear command and control; or if NATO, European, or U.S. troops engaged in ground combat with Russian forces.
Is Russia likely to use nuclear weapons?
Nuclear weapons have been a key issue in Russian-Ukrainian relations since the end of the Cold War. During the Soviet era, Ukraine was one of three non-Russian republics that hosted Soviet nuclear weapons. After independence in 1991, Ukraine joined the Treaty on the Nonproliferation of Nuclear Weapons as a nonnuclear weapon state. Ukraine also returned several thousand Soviet nuclear warheads to Russia (including 1,900 strategic nuclear warheads). In return, Ukraine got security guarantees from Russia, the United States, and the United Kingdom under the 1994 Budapest Memorandum. However, Russia violated this agreement in 2014 by annexing Crimea.
As early as 2014, Russian Foreign Minister Sergey Lavrov stated Russia’s willingness to use nuclear weapons to defend its territorial claims to Crimea. However, after its more extensive invasion of Ukraine in February 2022, Russia has faced embarrassing setbacks such as the loss of territory it had claimed was part of “Russian forever” and attacks on the Russian Black Sea Fleet in Sevastopol – without threatening a nuclear response. Some scholars, including Caitlin Talmadge, saw Putin’s willingness to mobilize large numbers of Russians as at least a short-term indication of an unwillingness to use strategic nuclear weapons.
In this year’s June/July TRIP survey – prior to Ukraine’s Aug. 6 invasion of the Russian oblast of Kursk – IR scholars did not think there was a high likelihood of Russia using nuclear weapons in Ukraine in the next two years. In fact, 74% thought there was a 20% chance or less that Russia would do so.
To be sure, as Alexander Montgomery and Amy Nelson have described, it can be very difficult to interpret numerical estimates of the likelihood of extremely rare events. One expert might view a 20% likelihood of using nuclear weapons as quite low, while another might view it as a relatively high risk. However, such data offers a baseline from which to measure how the same set of experts evaluate the increased risk from potential scenarios and how different types of scholars might disagree in their assessments of the likelihood of nuclear use.
So what scenarios might lead Russia to use nuclear weapons against Ukraine?
Scholars have warned about the risks of taking actions that would make Putin feel so threatened that Russia would respond with nuclear weapons. As Ukraine seeks to defend its territory (with the support of NATO, European countries, and the United States), these efforts risk making Putin take more aggressive and destructive actions. That includes possibly using nuclear weapons to avoid defeat. Some analysts and former policymakers, as well as Ukrainian policymakers, however, argue that Russia’s nuclear threats are largely empty. In their view, greater support to Ukraine will not increase the likelihood that Russia would use nuclear weapons.
The survey asked IR scholars to consider a range of possible scenarios involving actions taken by NATO, European countries, Ukraine, or the United States, and how likely they thought Russia would use nuclear weapons in response. IR scholars were especially skeptical that Russia would respond with nuclear weapons if either NATO or European or U.S. military personnel acting independently from NATO provided air defense against uncrewed Russian air assets and weapons in Ukrainian airspace. In this scenario, these countries destroy Russian drones and missiles launched against Ukrainian civilian or military targets. Survey participants were also highly skeptical that Russia would respond with nuclear weapons if NATO provided such air defenses for Ukraine.
When asked about NATO, European, or U.S. air defenses against crewed Russian air assets, respondents thought it was somewhat more likely that Russia would respond to such actions with nuclear weapons. These estimates were similar to how scholars assessed the likelihood that Russia would respond with nuclear weapons if Ukrainian forces retook Crimea, or if Ukrainian forces were allowed unrestricted use of Western weapons systems against targets inside Russia.
Foreign military engagement is another story
IR scholars thought it was more likely that Russia would use nuclear weapons in response to scenarios in which NATO, European, or U.S. forces engage in direct combat with Russian ground forces in Ukraine. Slightly over half (53%) of respondents thought there was more than a 20% chance of Russia responding with nuclear weapons in such scenarios.
But here’s the scenario IR scholars were most concerned about Russia responding with nuclear weapons: If Ukrainian forces attack Russian nuclear forces (command-and-control systems and/or military bases where nuclear missiles are located) in Russia with conventional weapons. Almost 60% of respondents thought there was more than a 20% likelihood that Russia would respond with nuclear weapons if this happened.
This scenario is not entirely implausible. Earlier this year, Ukrainian drones damaged Russian radar systems that provide early warning of a nuclear strike. The United States cautioned Ukraine that such actions raised the risk of nuclear escalation.
IR scholars had diverging views
Among those IR scholars surveyed, some important patterns of difference emerged. Women thought it was more likely that Russia would use nuclear weapons in Ukraine in the next two years. In fact, 43% of women thought there was more than a 20% chance of this, while only 20% of men thought so. IR scholars whose main area of focus is international or global security also assessed the risk of nuclear escalation differently from their colleagues who focus on other areas.
Scholars who specifically focus on international security generally thought that it was less likely that Russia would use nuclear weapons than those who focus on other areas. However, the difference was smaller than the difference between men and women. The survey found 19% percent of scholars who focus on international security thought there was more than a 20% likelihood that Russia would use nuclear weapons in the next two years of the war, compared to 28% of scholars focusing on other issues.
In general, international relations scholars do not think there is a high likelihood of Russia using nuclear weapons in Ukraine. But they are concerned about more aggressive actions raising the risk of a nuclear response. However, they don’t think Russia is more likely to respond with nuclear weapons based on whether the actions are taken by the United States, European countries, or NATO acting together. Instead, concerns about Russian nuclear use varied based on the specific action.
Naomi Egel is an assistant professor of International Affairs at the University of Georgia and a faculty fellow at the Center for International Trade and Security. Her research examines the dynamics of international security institutions, with a focus on the politics of multilateral weapons governance.
