Evidence of the unthinkable: Experimental wargaming at the nuclear threshold

Ongoing nuclear modernization programs in Russia, China, and the USA have reopened longstanding debates among scholars concerning whether tailored nuclear weapons are likely to have destabilizing consequences for international security. Without data to adjudicate this debate, however, these discussions have remained entirely theoretical. In this article, we introduce an experimental wargaming platform, SIGNAL, to quantify the effect of tailored nuclear capabilities on the nuclear threshold in a simulated environment. We then compare these results with a survey experiment using scenarios related to military basing, cyber operations, and nuclear threats from the wargame environment. While the survey experiments suggest that the presence of tailored nuclear capabilities increases the likelihood of conflict escalation, this trend diminishes in the wargaming context. Across both data-generating processes, we find support for the proposition that lower-yield nuclear weapons are used as a substitute for their higher-yield counterparts. These results have consequences for recent and ongoing policy debates concerning strategic posture and the future of arms control. This work also makes methodological contributions to the design and application of experimental wargaming for social science research, particularly for scenarios where data are limited or non-existent.