During the twentieth century, foreign-exchange intervention was sometimes used in an attempt to solve the fundamental trilemma of international finance, which holds that countries cannot simultaneously pursue independent monetary policies, stabilize their exchange rates, and benefit from free cross-border financial flows. Drawing on a trove of previously confidential data, Strained Relations reveals the evolution of US policy regarding currency market intervention, and its interaction with monetary policy. The authors consider how foreign-exchange intervention was affected by changing economic and institutional circumstances—most notably the abandonment of the international gold standard—and how political and bureaucratic factors affected this aspect of public policy.