This book articulates a cosmopolitan theory of the principles which ought to regulate belligerents' conduct in the aftermath of war. Throughout, it relies on the fundamental principle that all human beings, wherever they reside, have rights to the freedoms and resources which they need to lead a flourishing life, and that national and political borders are largely irrelevant to the conferral of those rights. With that principle in hand, the book provides a normative defence of restitutive and reparative justice, the punishment of war criminals, the resort to transitional foreign administration as a means to govern war-torn territories, and the deployment of peacekeeping and occupation forces. It also outlines various reconciliatory and commemorative practices which might facilitate the emergence of trust amongst enemies and thereby improve prospects for peace. The book offers analytical arguments and normative conclusions, with many historical and/or contemporary examples.