Ending wars right and justly has been an ethical imperative since they have first been fought. Given that the postwar periods of numerous wars fought in the recent past have been seriously bungled, the need for postwar ethics has become perspicuously clear. This need is also striking. It is striking because theories of jus post bellum have recently begun to take shape, yet they remain seriously deficient. Jus post bellum theorizing often remains narrowly focused on interstate warfare and is not reflective of the existing complexity and modalities of twenty first century conflict. In addition, current theories typically focus on punishment, recriminations, and backward–looking models of justice that do not necessarily prioritize relief and aid to war-torn soldiers, societies, and civilians. By theorizing the concept of jus post bellum as a forward-looking cosmopolitan model of justice, where the central task is on building a just and lasting peace through stabilization, aid, and development, this dissertation aims to fill this gap. In so doing, the dissertation seeks to broaden the scope of jus post bellum by connecting it, and the just war tradition more generally, with the emerging contemporary literature of cosmopolitan global justice.