Under what conditions do states use preventive military force to forestall or destroy an adversary’s nuclear weapons program? If nuclear weapons are so dangerous, why do leaders disagree about the magnitude of the threat posed by specific nuclear programs? Despite the fact that nuclear proliferation has been a growing source of concern, counter-proliferation decision-making remains poorly understood. In this Project on Managing the Atom Seminar, Rachel Whitlark will challenge existing explanations for this behavior, offer a new theory of counter-proliferation decision-making, and test its predictions in key historical cases.