The world is changing. We’re at a significant inflection point in world history.
President Joseph Biden, Jr.
U.S. Coast Guard Academy’s 140th Commencement Exercises, May 19, 2021
The United States and the world face serious threats to nuclear stability and peace, now and in the coming decades, and U.S. policy makers will need to make strategic decisions to both assist with long-term planning and react to unanticipated rapid changes in the nuclear arena. Examples include the following: the current war in Ukraine, nuclear developments in the Middle East and Northeast Asia over the years, potential nuclear proliferation by countries friendly to the United States, and the past decades’ security crises in South Asia. The threat of nuclear war erupting from non-nuclear conflict is not just a Cold War or immediate post-Cold War relic, but a matter of current and even urgent concern.
Despite the Nuclear Nonproliferation Treaty, nuclear arsenals are an openly documented reality in South and Northeast Asia; military conflicts among nuclear-armed Pakistan, India, and China have been ongoing since the 1990s;1 and Iran’s stockpile of enriched uranium continues to increase (IAEA, 2022). Russian troops’ unprecedented occupation of a commercial nuclear power plant in Ukraine presents yet another form of nuclear danger as of 2023 (Granholm, 2023), as does the documented interest in nuclear-explosive technologies expressed by certain terrorist groups since at least 2000.
At the same time, regional conflicts between countries with ties to great nuclear powers (United States, Russia, and China) are on the rise including Iran and Israel, India and Pakistan, and China and Taiwan.2 These many developments led to a declaratory shift in U.S. strategy from nuclear deterrence to integrated deterrence as described in the publicly available National Security Strategy and National Defense Strategy (Biden, 2022; DoD, 2022; see Box 1-1).3 Nuclear terrorism threats are also evolving as nuclear proliferation and an anticipated expanded use of advanced nuclear reactors among nation states increases opportunities for loss of material control and insider threats or possibilities of a nuclear state assisting terrorist groups. These shifts, and the increased U.S. policy focus on near-peer competition, are also present in the publicly available comments related to the National Security Memo (NSM) “U.S. Strategy for Countering WMD and Securing Nuclear and Radiological Materials.”4 Approaches to assessing risks of both nuclear war and nuclear terrorism to guide policy decisions should be able to accommodate and adapt to these shifts.
1 There have been numerous crises and military clashes and one war (Kargil War in 1999).
2 Great powers flexing their strength and regional conflicts of smaller states with great power allegiances are reminiscent of 1914 leading up to World War I. The difference between today and 1914 is that the great powers possess nuclear arsenals.
3 Previous administrations have similarly highlighted the need to expand the scope of deterrence across diplomatic, military and non-military (technological) domains, the U.S. interagency, spectrum of deterrence failures, and allies and partners—as noted in their National Security Strategies and Nuclear Posture Reviews (Clinton, 1994; Bush, 2002).
4 See the NSM-19 Fact Sheet, available at https://www.whitehouse.gov/briefing-room/statements-releases/2023/03/02/fact-sheet-president-biden-signs-national-security-memorandum-to-counter-weapons-of-mass-destruction-terrorism-and-advance-nuclear-and-radioactive-material-security.
To navigate the coming decades, the U.S. government leaders will need to rely on nuclear security and deterrence experts who will use a variety of methods to broadly assess the short- and long-term risks of conflict, anticipate adversary actions that could lead to nuclear war or terrorism, and understand the potential impact of U.S. responses to those actions. A key objective of risk analysis applied to nuclear war and nuclear terrorism is to avoid the catastrophic consequences of nuclear events, the challenge being to help decision makers identify, understand, and mitigate the impacts of a wide range of scenarios. Risk analysis, done well, provides important tools and results that can help address this challenge systematically, thereby offering decision makers a wider array of options and choices and potentially reducing the chances of nuclear destruction. It could address an issue identified by Thomas Schelling in his foreword to Roberta Wohlstetter’s Pearl Harbor: Warning and Decision (Wohlstetter, 1962):
There is a tendency in our planning to confuse the unfamiliar with the improbable. The contingency we have not considered seriously looks strange; what looks strange is thought improbable; what is improbable need not be considered seriously.
The committee was established and managed by the National Academies of Sciences, Engineering, and Medicine, in response to a congressional mandate (P.L. 116-92, 2019). Biographies for committee members are listed in Appendix A. Congress tasked the Department of Defense to contract
with the National Academies 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. The committee’s statement of task is reprinted in Box 1-2.
The committee’s work was conducted in two phases, without congressional oversight. Phase I produced an unclassified report (NASEM, 2023) focused on Tasks 1–3 of the statement of task and relied on unclassified, publicly available information. Specifically, within the Phase I report, Chapters 2 and 4, outline classes of scenarios and threats leading to nuclear war or nuclear terrorism; Chapter 3 explores the prior literature, and Chapters 5 and 6 discuss risk analysis including qualitative and quantitative methods and their applications to the nuclear risks problem set. The Phase I report laid the groundwork for Phase II by outlining methods that are used in risk assessment for a variety of applications. In Phase II, with access to classified briefings and reports up to the Secret level, the committee focused on Tasks 4 and 5 by exploring the use of risk methods to estimate the risks of nuclear war and nuclear terrorism and how the results are used to guide nuclear strategy. The committee also reviewed its Phase I responses to Tasks 1–3, in light of the additional classified information. This report is an abbreviated version of a longer report determined to contain Controlled Unclassified Information (CUI).
CONCLUSION 1-1: The Phase I report focused on Tasks 1–3 of the committee’s tasking. Although it contained no findings or recommendations, it produced a set of conclusions. Those conclusions were further supported by information gathered by the committee during Phase II (the classified phase), and the committee determined that the Phase I conclusions required no changes.
Risks of nuclear war have been affected by Russia’s 2022 invasion of Ukraine. In Phase II, the committee considered how U.S. strategic deterrence assessment of nuclear war risks have changed—or need to change—in response to the evolving threats of Russia’s invasion of Ukraine,5 as well as the emergence of two near-peer adversaries (Russia and China) and a nuclear-armed North Korea (USSTRATCOM, 2021).
This report is intended to provide an overview, guidance, and advice to the U.S. government on the development of risk assessments for nuclear war and nuclear terrorism in changing environments. The report will be equally relevant to the federal agencies and congressional committees who play a critical role in guiding and contributing to nuclear strategy and policy. In responding to the committee’s statement of task and in the context of this historical moment, the aim of this report is to identify how risk analysis tools are useful and can (1) improve the development of strategy for nuclear deterrence in the context of integrated deterrence, and (2) support decision making for countering nuclear terrorism.
The committee was briefed on and investigated the methods used by U.S. government and contractor analysts to assess risks of nuclear war and nuclear terrorism as well as the context and breadth of these analyses. It did not perform a risk assessment of nuclear war or nuclear terrorism, nor estimate those risks, but it did consider how risk assessments are conducted—by whom, on whose request, and with what assumptions—and how the assessments are used to guide strategy development.
In Phase I, the role of risk analyses (Task 2) was explored by considering and identifying approaches for assessing both the overall risk as well as more focused risks of nuclear war and nuclear terrorism. These focused risks, or components of the overall risk, include programmatic or technological risk such as estimating the reliability of a particular country’s nuclear stockpile; or determining the detection probability of a particular model of radiation detector at Ports of Entry. In Phase II, with access to classified information and discussions with U.S. analysts and decision makers, the committee was able to more deeply explore the roles that analytical methods play in estimating overall and more focused components of nuclear risks, the benefits of the risk analysis process, and the interface between risk analysis output and strategy development (Tasks 4 and 5).
Finally, the committee interpreted its statement of task as focusing on the methods of risks and strategies involving nuclear conflicts and risks of nuclear terrorist attacks against the United States. Nevertheless, it recognizes that a nuclear war or terrorist act anywhere would have profound ramifications everywhere around the world, the United States included.
This report contains four chapters and three appendixes. Chapter 1, this chapter, contains one conclusion. Chapter 2, “Risk Analysis,” outlines what risk analysis is, what it can do, and what constitutes good risk analysis (Box 2-1). Chapter 2 contains five findings and two conclusions. Chapter 3, “Development of Risk-Informed Strategies,” explores the interface between risk assessment and decision making in the context of changing U.S. deterrence strategy and countering weapons of mass destruction strategy guidance; one conclusion is made. Examples are also presented of how a new risk analysis capability to analyze the specific risks of deterrence failure leading to the use of nuclear weapons (a subset of the wider set of risks leading to integrated deterrence failure) might be implemented. Chapter 4 provides a short conclusion.
5 At the time of the Russian invasion into Ukraine (February 2022), the Phase I report had already entered the National Academies review process so the Phase I committee did not have an opportunity to collect information on the invasion’s impact on risk methods for assessing nuclear war and nuclear terrorism within the U.S. government, as noted in the Phase I Preface.
Appendix A contains the biographies of Phase II committee members, consultants, and staff. Appendix B is the set of questions developed by the committee to guide the content of presentations for invited speakers and briefers and for document requests to U.S. government agencies. Appendix C comprises the list of presenters and briefers during Phase II data collection.
As the United States continues to implement the expanded scope of integrated deterrence, there are multiple events that could signal deterrence failure. 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.