This dissertation consists of three self-contained essays that investigate the duration of war and the duration of postwar peace. The first essay studies both durations jointly, with a particular focus on the interdependence between the two processes. It demonstrates that membership in security organizations can prolong the durability of peace after conflict, but that the expected longer peace after conflict can also prolong the duration of conflict. The second essay analyzes the duration of war in a greater detail, exploring how third-party actors influence the process. It shows that balanced intervention can shorten the duration until a negotiated settlement is reached between the disputants. The third essay looks at the stability of postwar peace by focusing on the strength of cease-fire agreements. It argues that stronger agreements can maintain longer peace after wars by helping the disputants resolve the bargaining problems. The statistical analysis that corrects for the endogeneity of agreement strength provides support for the argument.