Charles Kupchan explores the conditions under which stable peace can be obtained, and more specifically how enemies become friends. He tells us that stable peace is a four phase process: accommodation, reciprocal restraint, deepening of social integration and generation of new narratives and identities. In order to illustrate his theory of stable peace, Kupchan gives us a number of concrete examples taken from history. Toward the end of the chapter Kupchan reflects on the future of the international system.