The intellectual history of just war thinking should be understood as unfolding in three traditions: the Augustinian, the Westphalian, and the Liberal. The Augustinian tradition of just war thinking rested on the idea that natural law exists and should guide human social and political order to fulfill natural human moral aspirations; that sovereignty means responsibility for the common good; and that justice should guide states to use force to defend the common good. In the Westphalian tradition, sovereignty evolved from defense of the common good to defense of international borders, and just cause shrank to encompass only territorial self-defense. In the embryonic Liberal tradition, concepts like human rights and accountable governance do the work that natural law and justice did in the Augustinian tradition: external standards outside and above the state used to judge the state’s legitimacy. The Liberal just war tradition allows war to vindicate the rights of individuals suffering under a humanitarian emergency, insists on respecting individual rights in how war is fought, and understands the vindication of individual rights a crucial part of ending wars justly.