Abstract: Why do some states agree to arms treaties while others fail to come to terms? I argue that the changing credibility of preventive war is an important determinant of arms treaty stability. If preventive war is never an option, states can reach settlements that both prefer to costly arms construction. However, if preventive war is incredible today but will be credible in the future, a commitment problem results: the state considering investment faces a “window of opportunity” and must build the arms or it will not receive concessions later on. Thus, arms treaties fail under these conditions. I then apply the theoretical findings to the Soviet Union’s decision to build nuclear weapons in 1949. War exhaustion made preventive war incredible for the United States immediately following World War II, but lingering concerns about future preventive action forced Moscow to proliferate.
Published in International Interactions.