Chemical weapons (CWs) were often portrayed as merely artifacts of history before 2012. Nuclear weapons still hold lasting geostrategic implications for deterrence with a fundamental and thus far unchallenged role in strategic stability. Biological weapons, whose uncertainty is driven by rapidly changing technological developments, were and remain a higher focus. As one third of the “weapons of mass destruction” (WMD) grouping of armaments, CWs are the “poor man’s atomic bomb.” The role of CW in state-based geopolitics was perceived by many as minor, if not out rightly dismissed as a tool of states in the twenty-first century, if thought of at all. For example, the Commission on the Prevention of Weapons of Mass Destruction Proliferation and Terrorism (aka the Graham-Talent Commission), a bipartisan U.S. congressional endeavor, refused to consider chemical weapons in its final report in 2008. Spelling out the type of WMD to which they were referring, they observed that “terrorists are more likely to be able to obtain and use a biological weapon than a nuclear weapon.” The Commission declared that “unless the world community acts decisively and with great urgency, it is more likely than not that a weapon of mass destruction will be used in a terrorist attack somewhere in the world by the end of 2013.” Their prediction was correct in its timing. By December 2012, it was a state regime, Assad’s Syria, which used chemical weapons and employed them multiple times as part of its civil war.

Countering WMD has been among the highest priorities for the U.S. domestic and the international security communities in the twenty-first century. Denying the acquisition and use of WMD by hostile states, substate actors, or nonstate actors as part of nonproliferation and counterproliferation, coupled with possessing robust capacity to manage potential consequences are desired strategic ends. Prevention of WMD development and use is a laudable aim, but disparities between that objective and the understanding of the geostrategic implications of chemical (and biological) weapons remain as a comparatively nascent and undertheorized field to the rich theoretical work that underpins nuclear proliferation, deterrence, and strategic stability.

Greater recognition of that is needed in order to affect strategy and to enable additional policy levers. Part of the challenge in narrowing the gap between strategy and its enabling capabilities and capacities are attributable to multiple endogenous and exogenous military, technical, cultural, policy, and institutional factors. Works like Coercing Syria on Chemical Weapons and others (Koblentz, Gregory. 2013. Contemporary Security Policy, 3(3); Bleek, Philipp C. and Nicholas J. Kramer. 2016. The Nonproliferation Review 23(1–2); Kosal, Margaret E. 2018. PRISM, 7(3); Chapman, Geoffrey, Hassan Elbahtimy, and Susan B. Martin. 2018. Security Studies, 27(4)) are necessary if we are to close those gaps for chemical weapons, as well as biological weapons (BWs). Robust analytically driven understanding of CW (and BW) also has implications for understanding the international security implications of emerging technologies.

The crux of the question motivating and underlying Coercing Syria on Chemical Weapons is how “to better understand the potential uses and limitations of coercive strategies,” (p. 11) and of recent evolutions of “tailored” and “cross-domain” deterrence. Overall, this is an innovative and timely work that significantly advances the understanding of coercive diplomacy, that is, compellence and deterrence as it plays out (or does not) in reality. It is deeply grounded in the theoretical literature, which is used to assess and analyze the complications of trying to elucidate specific causal mechanisms and pathways by which coercive diplomacy unfolds.

This substantive work by Moran, Bowen, and Knopf is highly recommended for those interested in wider issues of deterrence in the modern world. Chapter 2 provides an excellent framing of the broader topic of coercive diplomacy in context of the CW use by Syria. The discussion of credibility and what it means (and likewise does not mean) is particularly nuanced and useful (pp. 34–48). Chapter 3 provides historical and geopolitical background for Syria’s chemical weapons program, including a notable Assad regime connection to Soviet doctrine and how that may have shaped Syria’s strategic calculus. U.S. policy and strategy, especially in context of CW (and BW), has been constructed in context of Iraq’s WMD programs in the 1990s rather than Soviet conceptions of CW use in insurgent situations. In a time when the United States and others have shifted to great power competition as strategy, it demonstrates how lessons related to countering insurgents, low intensity conflict (LIC), and terrorists still matter. This may also have implications in context of allegations of CW use by Russia in its illegal war against Ukraine.

Chapter 4 elucidates how difficult it is to isolate single causal factors in context of a state issuing a deterrent threat (the United States) or a state being subjected to one (Syria). Given the limited insight we had into Assad’s military calculus, this discussion breaks down multistep complex interactions to show how, in particular, ambiguity in terms of what constituted use—type of agent or severity of attack as measured in casualties (small-scale versus large scale)—plays into what is commonly portrayed as a clear-cut statement, that is, President Obama’s “red line” comment. It was actually much more complicated than is commonly perceived. In Chapter 5, they note that the “red line” explanations and subsequent actions by the Obama administration were taken seriously enough by the Russian regime for Putin to push his foreign ministry to pressure Assad to demilitarize and accede to the Chemica Weapons Convention (CWC) (pp. 170–176). The negotiations leading to and the execution of the initial removal of CW from Syria was one of the most complicated and seriously impressive efforts inside the USG and with multiple partner states.

Chapter 6 analyzes the challenges of trying to use coercive diplomacy when a state has been duplicitous, i.e., not fully in compliance with the CWC, and while two major diplomatic actors make substantial changes. Russia’s focus shifted away from Syria to their own activities, that is, Russia’s illegal annexation of Crimea in 2014, and the U.S. administration changed in 2017. Chapter 7 wraps up the main part of the book with particularly well-developed policy lessons.

CWs have been used both by military forces on the battlefield and by terrorists in cities and towns in the twenty-first century. In this respect, they truly are unique among the weapons of mass destruction. Understanding the limits and strengths of different policy approaches (National Academies of Sciences, Engineering, and Medicine, Chemical Terrorism: Assessment of U.S. Strategies in the Era of Great Power Competition, 2024) to reducing the threat of chemical (and biological) weapons remain important strategic and scholarly aims. More empirically-driven, analytic work, like Coercing Syria on Chemical Weapons, is needed to develop and advance theories that help explain the why states decide to pursue chemical and biological weapons programs, how to counter them, and the geostrategic implications of technologies relevant to proliferation, whether by states or nonstate actors. Better theoretical work should enable better policies for prevention and limiting the proliferation of such weapons and responding to unwanted proliferation. The work reviewed here is an important piece in understanding the calculus states use in deciding to pursue, develop, and use unconventional weapons.