About the event: A cross-national shift toward lower-yield nuclear weapons has generated renewed interest in crisis dynamics near the nuclear threshold. Lower-yield nuclear weapons alter nuclear nonuse mechanisms of credibility, costliness, and normative inhibitions. In comparison to higher-yield, city-destroying nuclear weapons, the lower-yield weapons offer a less costly and therefore more credible deterrent. But by reducing costliness, they also undercut norms grounded in the devastating effects of nuclear weapons. With Kristyn Karl and Matthew Wells, I conducted nationally representative survey experiments in India and Pakistan, and in the United States and United Kingdom, to investigate how citizens consider low-yield nuclear weapons use in an escalating crisis. We offered low-yield nuclear weapons as one of three possible retaliatory strike options in different crisis scenarios, some of which involved a low-yield nuclear attack by the adversary, and we varied the vividness of information we provided about the unique effects of a nuclear explosion. We also examined how beliefs about retribution and feelings toward citizens in the rival country affect willingness to use nuclear weapons. Across the four national samples, we found evidence of both nuclear restraint and permissiveness. In three of the four countries, respondents were more willing to use nuclear weapons in retaliation if the adversary first crossed the nuclear threshold by conducting a low-yield nuclear strike. In all four samples, larger proportions of respondents preferred lower-yield to higher-yield nuclear retaliation. These and other main findings, which I will present for each of the two pairs of survey experiments, complicate theoretical understandings of the conventional-nuclear threshold and have broad implications for both deterrence mechanisms and nuclear non-use norms.

About the speaker: Lisa Langdon Koch is Associate Professor of Government at Claremont McKenna College, specializing in international relations. She is the author of Nuclear Decisions: Changing the Course of Nuclear Weapons Programs (Oxford University Press, 2023), which won the Robert Jervis Best International Security Book Award. She has published numerous articles on topics like nuclear proliferation and foreign policy. Her research has been funded by the Stanton Foundation Nuclear Security Grant Program and the Carnegie Corporation of New York. In 2023, Koch received the Glenn R. Huntoon Award for Superior Teaching. She is a 2000 Harry S. Truman Scholar.

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