Why do cease-fire agreements sometimes last for years while others flounder barely long enough to be announced? How to maintain peace in the aftermath of war is arguably one of the most important questions of the post--Cold War era. And yet it is one of the least explored issues in the study of war and peace. Here, Page Fortna offers the first comprehensive analysis of why cease-fires between states succeed or fail. She develops cooperation theory to argue that mechanisms within these agreements can help maintain peace by altering the incentives for war and peace, reducing uncertainty, and...