To explore these issues, the CSIS Project on Nuclear Issues recently compiled a database and released a digital report Russian nuclear narratives and their evolution during the first 18 months of the war. This brief builds on that work and finds that Russian officials noticeably calibrated their nuclear signaling at key points in the war. It also concludes that the risks of nuclear use will likely rise if Russia faces significant battlefield setbacks in the future or the conflict expands in new or unexpected ways. Accordingly, Washington should work to maintain international pressure against nuclear use in Ukraine while combatting narratives that downplay or rationalize Russia’s nuclear threats.
Introduction
A nuclear shadow has loomed over the war in Ukraine since Russia invaded on February 24, 2022. Following a large-scale nuclear exercise, Putin announced a “special military operation” as Russian troops crossed the border and threatened, “No matter who tries to stand in our way or all the more so create threats for our country and our people, they must know that Russia will respond immediately, and the consequences will be such as you have never seen in your entire history.”
Russia’s nuclear signaling—its deliberate efforts to influence foreign decisionmaking through the implicit or explicit threat of nuclear use—is part of its wider strategy to deter direct Western intervention and support for Ukraine. Moscow has used explicit threats, including mention of crossing a “red line” in September 2022 if the United States supplied longer-range missiles to Ukraine, as well as implicit threats such as frequent reference to Russia’s nuclear doctrine. Russia has also used disinformation campaigns, exercises, and new nuclear force deployments to Belarus to manipulate risks and attempt to weaken Western support for Ukraine.
Russia’s nuclear rhetoric and posturing have made the risk of nuclear weapons use the highest it has been for decades and revived calls for new risk reduction efforts.[4] Amidst these rising nuclear risks, however, Russia is working to weaken the institutions and norms designed to manage those very risks. Since the February 2022 invasion, Russia has blocked consensus on the Nuclear Non-Proliferation Treaty, suspended the New Strategic Arms Reduction Treaty (New START0, and withdrawn its ratification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT).The success or failure of Russia’s nuclear signaling in Ukraine will have wider strategic implications. In a December 2023 speech, U.S. secretary of defense Austin stated, “If we do not stand up to the Kremlin’s aggression today, if we do not deter other would-be aggressors, we will only invite more aggression, more bloodshed and more chaos.” Indeed, other countries are likely watching and learning from how Russia is brandishing its nuclear weapons.
On the one hand, Russia’s nuclear signaling may have successfully deterred the North Atlantic Treaty Organization (NATO) states from directly engaging in the war, particularly in the early stages.[7] On the other hand, NATO may have never been willing to put “boots on the ground” in Ukraine—meaning the United States and NATO were never deterred from doing something they never intended to do. A more nuanced understanding of how Russia’s nuclear signaling has evolved since the February 2022 invasion, along with the impact of messaging from NATO and external actors—particularly China and India—can shed light on Russia’s reliance on nuclear weapons and the role of nuclear weapons in the Ukraine war and beyond. Russia’s nuclear signaling, including rhetoric and actions, has evolved since the beginning of the war and is not static. Instead, officials in Moscow noticeably calibrated their nuclear messaging, ramping up their threats in the face of setbacks on the battlefield while at times showing a receptiveness to external pressures. With the war far from over, Washington, Kyiv, and NATO should expect to see continued calibration in the coming months and years.
Russia’s nuclear rhetoric and posturing have made the risk of nuclear weapons use the highest it has been for decades and revived calls for new risk reduction efforts. Amidst these rising nuclear risks, however, Russia is working to weaken the institutions and norms designed to manage those very risks.
This brief assesses the impact of Russian nuclear signaling on the war in Ukraine, the effectiveness of Western de-escalation efforts, and whether or not Putin would consider using nuclear weapons in the future. It draws on a wider CSIS study of nearly 450 public statements, policy announcements, and military developments in the first 18 months of the war. The brief first provides background of the nuclear shadow leading up to the war in Ukraine, with a summary of Russian nuclear capabilities and doctrine. It then summarizes Russian nuclear activities across three phases of the conflict: February–July 2022, August–October 2022, and November 2022–July 2023, although arguably, Russian nuclear signaling began even before the invasion, such as with the nuclear exercise in February 2022. The brief concludes with findings and recommendations for Western policymakers on how to respond to Russian nuclear bullying and de-escalate crises with the potential for nuclear use.
This brief’s overarching finding is that leaders in Moscow escalated their nuclear signaling when facing battlefield setbacks, a trend that will almost certainly continue. Russia has relied on a range of signals and implicit and explicit nuclear threats in an attempt to deter NATO intervention in Ukraine and divide the alliance. As the intelligence community assessed in its 2023 annual threat assessment, “Moscow’s military forces have suffered losses during the Ukraine conflict that will require years of rebuilding.” As a result, U.S. intelligence sources conclude, “Moscow will become even more reliant on nuclear, cyber, and space capabilities as it deals with the extensive damage to Russia’s ground forces.” Navigating these challenges will require policymakers to assess and manage the enduring nuclear shadow looming over the war in Ukraine.
Russian Nuclear Forces and Doctrine
Nuclear weapons play a fundamental role in Russia’s deterrence strategy. The declaratory policy governing their use has gone through four iterations since the end of the Cold War. The Kremlin implemented the first changes to its nuclear policy in the 1993 military doctrine, which eliminated mention of the “no first use” policy that Russia inherited from the Soviet Union. This omission suggested that Russia could use nuclear weapons to counter significant conventional aggression, and it likely reflected the Kremlin’s concerns about Russia’s diminished conventional military power and U.S. precision strike capabilities demonstrated during the Gulf War. Russia’s 2000 military doctrine—released less than a year after NATO’s intervention in Kosovo—stated that Russia could use nuclear weapons in response to nuclear attacks, attacks using other weapons of mass destruction (WMD), and certain types of conventional attacks on its territory.[13] Building on this policy, the 2010 military doctrine stated that Russia could use nuclear weapons in response to an attack against Russia or its allies using WMDs, or in response to a large-scale conventional attack against Russia that threatens “the very existence of the state.” This language went unchanged in Russia’s 2014 military doctrine.
In 2020, the Kremlin published its first declassified nuclear doctrine (as opposed to military doctrine), which made explicit two additional factors that could provoke a Russian nuclear response. This document lists four scenarios for nuclear employment[16]:
- Receipt of reliable data about the launch of ballistic missiles against Russia or its allies
- Use of nuclear weapons or other weapons of mass destruction (WMDs) against Russia or its allies
- Attacks against Russian nuclear command, control, and communications infrastructure
- Aggression against Russia with conventional weapons that threatens “the very existence” of the Russian state
Numerous questions remain about the specifics of Russia’s nuclear doctrine. Of particular importance is the question of whether Putin draws a distinction between the Russian state and his own regime. Given the risks that Putin has taken in his efforts to gain political control over Ukraine, it is possible that he believes defeat would pose a threat to the “very existence” of his rule. Independent of its declaratory policy, experts assess that the Kremlin could use nuclear weapons in a regional conflict to control escalation and signal resolve.
As of summer 2023, Russia had an estimated stockpile of approximately 4,489 active nuclear warheads for use on strategic and theater-range delivery systems—1,197 on intercontinental ballistic missiles (ICBMs), 896 on submarine-launched ballistic missiles (SLBMs), 580 on bombers, and 1,816 on a wide range of nonstrategic systems. Only 1,674 warheads, however, are currently deployed. “Deployed” warheads are mated to delivery systems and ready for immediate use. “Reserve” warheads are kept in storage, often partially disassembled.
