No nuclear weapons have been used in combat since 1945. Their influence on the Taiwan Strait is nonetheless pervasive and structural. The nuclear arsenals of the United States and China — and, less directly, those of Russia, Britain, and France — shape every aspect of the conventional military competition in the strait, the escalation calculus that each party brings to crisis management, and the limits that major power decision-makers apply to their own coercive behavior. Understanding Taiwan Strait risk without understanding the nuclear dimension is understanding a building without understanding its foundations.