War and peace are often seen as the two elemental states of affairs in international relations. When hostilities erupt, the task of diplomacy is to end the violence and reestablish peace. But some armed conflicts between states endure, resisting final settlement but persisting in a state short of total war. The Cold War struggle between the United States and the Soviet Union is perhaps the most prominent example. Blum argues that these sorts of protracted armed rivalries are often better managed rather than solved, because seeking full settlement is to invite endless frustration and danger while missing opportunities for more limited but stabilizing agreements. She provides a nice depiction of the special logic of these "mixed motive" conflicts, in which neither party is willing to resolve the core contested issues but both may be willing to carve out specific areas of their relationship to be regulated -- what Blum calls "islands of agreement." The book offers detailed historical accounts of three prominent enduring rivalries: between India and Pakistan, Greece and Turkey, and Israel and Lebanon. In each case, Blum illuminates the ways in which governments open their countries to specific accommodations even as the overall conflict -- and the suffering of citizens and soldiers -- continues. The book has a tougher time answering the larger and trickier question of whether these "islands of agreement" provide incremental steps toward peace or undercut the constituencies for a more sweeping and permanent settlement.