Since the closing days of the Cold War, U.S. policymakers, pundits, international relations scholars, and policy analysts have argued that great-power war is a relic of a bygone age. In 1986, the historian John Lewis Gaddis termed the post–World War II era a “Long Peace” because the Soviet Union and the United States had not come to blows. A few years later, the political scientist John Mueller suggested that changing norms had made great-power conflict obsolete. By 2011, the psychologist Steven Pinker was arguing that the Long Peace had morphed into a “New Peace,” marked by a generalized...…Since the closing days of the Cold War, U.S. policymakers, pundits, international relations scholars, and policy analysts have argued that great-power war is a relic of a bygone age. In 1986, the historian John Lewis Gaddis termed the post–World War II era a “Long Peace” because the Soviet Union and the United States had not come to blows. A few years later, the political scientist John Mueller suggested that changing norms had made great-power conflict obsolete. By 2011, the psychologist Steven Pinker was arguing that the Long Peace had morphed into a “New Peace,” marked by a generalized...WW…