The United States and the world face serious threats to nuclear stability and peace, now and in the coming decades. Within the nuclear arena, U.S. policy makers will need to make strategic decisions related to nuclear risks to assist with long-term planning as well as responding in real time to unanticipated events. The occurrence of unanticipated nuclear events is expected to increase as more countries develop, expand, or field nuclear energy capability; more countries consider development of nuclear weapon capability and new nuclear weapon states emerge; and nuclear weapon states expand their nuclear arsenals. For the first time ever, a nuclear armed power is threatening the use of nuclear weapons during a large-scale conventional war and is occupying an operational civilian nuclear power plant in an ongoing conflict.
The United States’ most recent National Security Strategy recognizes these expanded threats through a change in phrasing from nuclear deterrence to integrated deterrence (Biden, 2022). While the Biden administration is the first to use the term “integrated deterrence” in its national security documents, National Security Strategies and Nuclear Posture Reviews from previous administrations similarly highlighted the need to expand the scope of deterrence.1 A common thread between the past and the current national security documents is that an integrated deterrence strategy is needed to address security environments that are complex and dynamic. Despite these complex and interconnected changes, the U.S. government assessments of nuclear risks are conducted within federal agencies that may be well-suited to address agency-specific needs but limit a wider consideration of factors contributing to overall risks connected to the use of nuclear weapons.
The Committee on Risk Analysis Methods for Nuclear War and Nuclear Terrorism was established and managed by the National Academies of Sciences, Medicine, and Engineering in response to a congressional mandate (P.L. 116-92, 2019) to independently explore U.S. government methods for assessing nuclear war and nuclear terrorism risks and how those assessments are used to develop strategy and policy. Key findings and conclusions of the committee are provided below.2
FINDING 2-1: Risk analysis when conducted well, can provide a systematic and disciplined approach; illuminate threats, vulnerabilities, and consequences; and analyze complex interactive situations and dependencies among events. Good risk analysis has leadership guidance and support, informs leadership, and includes scenarios and exercises.
FINDING 2-3: A well-performed risk analysis is decision focused, explicit about objectives, incorporates creative alternatives, addresses all relevant outcomes, characterizes uncertainties through development of scenarios and exploration of dependencies, addresses changes to risks over time, and supports transparent discovery and policy deliberation. These define, in part, fundamental principles of risk analysis.
1 For example, integrating elements of statecraft in support of national security strategy (including deterrence) appears at least as far back as the Clinton administration’s National Security Strategy documents (Clinton, 1994). The George W. Bush administration’s 2002 National Security Strategy also focused explicitly on leveraging advanced conventional weaponry to support nuclear deterrence missions, thereby reducing reliance on nuclear weaponry (Bush, 2002).
2 The numbering of the findings and conclusions follows the numbering in the report and thus may not appear consecutively in the Summary.
CONCLUSION 2-1: The benefit of a well-performed risk analysis is that it prompts those requesting the analysis, who may have decision-making biases, to work in conjunction with those conducting the risk assessment to develop, for example, a systematic listing of potential outcomes; the pathways that can lead to those outcomes; and underlying assumptions, including correlations (dependencies) between different paths and outcomes.
There are many examples of risk analysis being used within the U.S. government to guide targeted questions related to components of nuclear terrorism risks or nuclear war risks, but few consider the wider-scoped questions of the overall risk of nuclear terrorism or overall risk of nuclear war.
Integrated deterrence expands the scope of deterrence to encompass multiple domains, including military and non-military (i.e., diplomatic, economic, technological, and information) domains, geographic regions, U.S. government agencies, and its allies and partners. It also intertwines conventional weapon and nuclear weapon use strategies.3 The implementation of integrated deterrence will require coordination across a number of domains to enhance factors not previously emphasized within U.S. deterrence strategy.
CONCLUSION 3-1: Deterrence is an enduring strategic concept that needs constant rethinking and adaptations that are tailored to fit new and existing adversaries, changing contexts, and new circumstances. The U.S. government has acknowledged an expanded scope for deterrence as integrated deterrence, which seeks new ways to integrate contributions to deterrence across multiple domains (e.g., military and non-military organizations, U.S. agencies, and geographic regions). In this effort, the risk of deterrence failure leading to the use of nuclear weapons becomes one part of a larger set of risks. Due to the potentially catastrophic consequences of nuclear weapons’ use, the U.S. government must recognize and prioritize the need to develop specific assessments of the risks of nuclear weapons use while implementing an integrated deterrence strategy.
Examples where risk analysis could contribute include the following: new strategic conditions with two or more adversaries with large nuclear arsenals; domestic and foreign terrorist organizations with possible connections between them; adversaries capable of creating strategic effects using cyber warfare; and adversaries with other weapons of mass destruction (i.e., biological, chemical) and adopting first-use doctrines.
The ability to maintain deterrence in peace and restore deterrence in war will be strongly influenced by thoughtful and well-done risk analysis that considers a wide range of possible outcomes—not simply the most probable or worst case. The United States has much that it can do to improve that ability.
3 Integrated deterrence is “the seamless combination of capabilities to convince potential adversaries that the costs of their hostile activities outweigh their benefits” (Biden, 2022, p. 22). Also, see Box 1-1. With the expanded scope, there are multiple events that could signal a failure of integrated deterrence. For the purposes of this report and its focus on the risks associated with the use of nuclear weapons (which pose an existential threat), the committee chose to highlight integrated deterrence failures associated with the use of nuclear weapons at any level. The committee recognizes that some policy choices could include the use of nuclear weapons as a way to limit further escalation and that this may not be considered by some as a failure of deterrence.