Scholars have noted that a very small group of states is responsible for most interstate disputes and wars. These strategic rivalries last for decades, periodically flaring up to threaten peace and security. This book represents one of the best efforts yet to understand why they emerge, persist, and, most important, end. The authors argue that de-escalation occurs when adversaries assume new understandings and expectations of their opponents. Such shifts sometimes occur after a crisis or shock pushes leaders in one or both states to question the viability of the conflict. The warming of U.S.-Chinese relations in the early 1970s, for example, was preceded by various shocks: the Tet offensive in Vietnam, Sino-Soviet border clashes, and the trauma of the Chinese Cultural Revolution. Shifts can also take place after new leaders come to power with new expectations, as was the case with the Egyptian-Israeli rivalry, which persisted for decades and subsided only after significant changes in both countries’ governments. The book might lead readers to wonder what sort of shock in Northeast Asia might fundamentally reorient relations between North and South Korea.