What kind of nuclear forces are enough to deter conflict? International security literature evinces a pervasive ‘existential bias,’ arguing that the mere possession of a small nuclear arsenal ought to deter adversaries from initiating conflict. Kenneth Waltz famously argued that nothing more than the “credibility of small deterrent forces” is required to establish Thomas Schelling’s “threat that leaves something to chance,” and ought to deter not just nuclear use but conventional attacks as well (Waltz and Sagan 2002, p. 23; Schelling 1960). Existing quantitative work on nuclear deterrence and conflict explicitly expresses this bias by treating all nuclear states as equivalent once they acquire a single nuclear weapon. This assumes that a state with one warhead reaps the same deterrence effect as states with mature second-strike or even first-use capabilities.