As the United States gears up for a presidential election and the administration juggles support to Ukraine, growing conflict in the Middle East, and a host of other challenges, Washington will need to address five key nuclear weapons challenges in 2024. Managing Russia’s nuclear threats, China’s opaque nuclear buildup, and North Korea’s increasing provocations—and the increasingly close relationships among them—will be no easy feat. At the same time, Washington will need to navigate its extended deterrence commitments and efforts to better integrate with U.S. allies and finally organize for a series of consequential, long-term decisions on the future of the U.S. nuclear arsenal. While a high-intensity war with China or Russia or a major conflict with North Korea is not inevitable, the pathways to potential conflicts are increasing, and so too are the risks of nuclear use—especially limited nuclear use. With an exceedingly complex international security environment, policymakers, planners, and legislatures need to think about the unthinkable this year and take action. Deterring nuclear use requires a sober assessment of the new and changing ways adversaries are attempting to leverage nuclear weapons and clear-eyed plans for how to manage nuclear threats if deterrence fails. Here are the top five nuclear issues to address in 2024: 1. Russia’s Nuclear Threats and the War in Ukraine As the war in Ukraine enters its third year and the administration and Congress debate future U.S. security assistance to Ukraine, a key question will be how Russia’s nuclear signaling and threats will evolve in 2024 and how the trajectory of the conflict will affect the potential for nuclear use. While the risk of use likely remains low amid the current stalemate, significant changes on the ground, such as a significant spike in attacks deep inside Russia, could affect that calculus. In addition, with increased cooperation between Russia and North Korea (and Iran) and confirmation that North Korea is providing Russia with ballistic missiles and ballistic missile launchers, another key question will be to what extent this kind of assistance affects the situation on the ground, whether this prolongs the conflict, and how this affects overall escalation dynamics. With the intelligence community assessing that “Moscow will become even more reliant on nuclear, cyber, and space capabilities as it deals with the extensive damage to Russia’s ground forces,” nuclear risks could actually grow in the coming months and years, making it essential that Washington, NATO, and Kyiv remain prepared and clear-eyed about how to handle a range of scenarios, especially those involving “battlefield” nuclear weapons and limited nuclear use. In addition, while U.S. officials have indicated that they have not yet seen changes to Russia’s strategic nuclear forces since it suspended New START, without onsite inspections or data exchanges, it may become more difficult over time to maintain confidence that there have been no militarily significant operational changes to Russia’s strategic forces using national technical means alone. This means there will be very few guardrails on the broader U.S.-Russia strategic relationship, making it—as well as Russia’s efforts to deliberately manipulate nuclear risks in Ukraine and beyond—one of the top nuclear issues to watch in 2024. 2. China’s Nuclear Buildup China’s rapid expansion and diversification of its nuclear forces also demands attention in 2024. While the administration has made clear that “the United States does not need to increase our nuclear forces to outnumber the combined total of our competitors in order to successfully deter them,” a number of recent high-profile commissions, reports, and studies argue for important changes to U.S. nuclear forces, setting up a renewed debate over what’s driving China’s nuclear buildup and whether and how the United States should respond. China’s nuclear buildup cannot be viewed in isolation, however. This is fundamentally a question of whether the United States has the necessary force structure to manage concurrent or sequential conflicts with two nuclear-armed adversaries—a force-sizing construct the Pentagon abandoned years ago (and never truly had to address in the same way). At the same time, the debate over potential changes to the size and composition of U.S. nuclear forces cannot mask questions over how Washington and its allies would respond to Chinese nuclear coercion or even limited nuclear use in certain scenarios, particularly a Taiwan crisis. Such a crisis could occur well before any changes to the current program of record materialize, and China is no doubt watching how Russia is deliberately manipulating nuclear risks in the war in Ukraine. With continued cross-Strait tensions and an uncertain future for the broader U.S.-China relationship, it is essential that officials understand the conditions under which China might use nuclear weapons and be prepared to manage the nuclear shadow that will loom over virtually any conventional conflict in the Indo-Pacific. Arms control talks with China may help improve this understanding over time, but recent efforts to engage on these issues are unlikely to translate into a reliable risk reduction mechanism any time soon or change the operational dilemmas U.S. forces might encounter. This means that Washington and its allies need to deepen planning and consultations in 2024 on managing the nuclear shadow with China for if and when a conflict occurs and ensure that these efforts are fully integrated into broader defense planning efforts. 3. Tensions with North Korea and Opportunistic Aggression In his New Year address, Kim Jong-unn warned that North Korea needs to prepare for war with the United States in 2024 and pointed to the U.S.-Republic of Korea (ROK) Washington Declaration, increased trilateral exercises, and the more visible presence of U.S. strategic assets as the reason behind the North’s aggressive posturing. While to some extent, this kind of rhetoric and blame game is more of the same—especially in an election year—North Korea’s continued quantitative and qualitative growth of its nuclear and ballistic missile programs, including both long-range systems capable of striking the United States and its increasing emphasis on tactical nuclear weapons, pose serious threats to the United States, ROK, and Japan that cannot be ignored or wished away. Washington and Seoul cannot deter missile tests or satellite launches, but they can take steps to ensure U.S. and ROK forces are prepared for both major conflicts as well as localized attacks, which can in turn help deter a war that no one wants. This requires consistently updating plans and assumptions, clarifying roles and responsibilities, and maintaining readiness for a wide range of North Korea contingencies. Maintaining this focus can be difficult given all of the demands on U.S. forces and the attention on great power competition, but it is essential. At the same time, tensions on the Korean Peninsula don’t exist in a vacuum, and possible North Korean contingencies or conflicts cannot be planned against in isolation. As North Korea and Russia step up their cooperation, ties between Russia and China increase, and China and North Korea rekindle links, 2024 will unfortunately likely serve as a reminder that it is not enough to focus on managing individual flashpoints with Russia and China. If the United States finds itself in a conventional conflict with China or Russia, it could provide a dangerous opening for North Korea to exploit, just as a conflict with North Korea could leave the United States and its allies dangerously unprepared to manage a bubbling over of tensions with Russia or China (Russia and China could also of course take advantage of regional conflicts in separate theaters, which would pose even greater constraints). Understanding and better preparing for the risks and tradeoffs associated with these types of opportunistic aggression scenarios, whether coordinated or not, should be a top priority in 2024. This will require, among many things, difficult and frank consultations on the limitations and possible roles and responsibilities across various alliance structures in the Indo-Pacific, as well as with NATO allies. 4. U.S. Extended Deterrence Commitments and Integration with U.S. Allies U.S. allies are understandably skeptical over whether the United States can and will maintain its alliance commitments. Managing these concerns—especially in an election year—will require continued time and attention, a requirement many U.S. allies in Europe and Asia worry could be increasingly difficult given the upcoming election and deteriorating situation in the Middle East and the demands the region is once again placing on U.S. officials. The Biden administration took important steps in 2023 to strengthen alliances and extended deterrence assurances to U.S. allies, and deepen planning and coordination on key crisis management issues. Finding ways to institutionalize and deepen these efforts will be critical. These efforts should focus on a range of possible conflict scenarios with Russia, China, and North Korea and dig into some hard questions: What specifically do various alliances intend to deter? Who would do what in a crisis? What might be perceived as escalatory? How would allies communicate with one another and the public during a contingency? How might various alliances might integrate conventional and nuclear operations during a crisis, or take certain actions to deter opportunistic aggression? It will also be important to watch how Washington postures its nuclear forces over the next year to both assure allies and demonstrate its readiness and resolve to U.S. adversaries. The United States has shifted to a much more dynamic mode of messaging and communicating its nuclear force movements—from a significant uptick in bomber task force missions to a much more visible presence for U.S. ballistic missile submarines. Going forward, officials need to take a holistic look at what effect these measures have (and what the implications for future force management decisions might be) and find opportunities to monitor how certain actions or exercises in one theater register, or not, with adversaries in another. 5. Progress on U.S. Nuclear Modernization Finally, with such a dynamic threat environment, 2024 will be a critical year for the nuclear enterprise. Every major element of U.S. nuclear forces is being modernized. But delays, budget overruns, supply chain issues, and significant workforce and infrastructure constraints across both the defense and national lab sectors are leading to an increasing disconnect between policy debates over what might be needed in the future and the reality of what the existing workforce and infrastructure can support. This needs to change in 2024. Congress needs to change the way it oversees defense and National Nuclear Security Administration programs and work with the Pentagon to enact significant changes to the way the enterprise assesses risks—not just the risks of delays across the nuclear enterprise but also to conventional acquisition programs that are critical to our ability to deter, and prevail in, if necessary, a high-intensity conflict. To be clear, this is not just a resourcing issue. Service members will soon be operating both legacy and replacement systems concurrently—a challenge the U.S. Air Force and Navy have not encountered for decades. Managing these issues requires leadership and careful attention from the highest levels—a commodity that is often in short supply. Unfortunately, these are far from the only challenges the United States and its allies will have to contend with in 2024. Washington will also have to manage the growing proxy war with Iran and ongoing concerns about its nuclear program, as well as a host of other nonproliferation challenges. Thinking about the unthinkable in 2024 does not mean reviving Strangelovian concepts from the Cold War. Instead, it is about being realistic about the potential for direct conflicts with Russia, China, or North Korea and wrestling with a more difficult and uncomfortable question: If the United States goes to war, is it prepared to manage nuclear coercion and respond to potential nuclear use? Kelsey Hartigan is deputy director of the Project on Nuclear Issues and senior fellow with the International Security Program at the Center for Strategic and International Studies in Washington, D.C. Commentary is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s). © 2024 by the Center for Strategic and International Studies. All rights reserved.