In this masterful history, Douglas chronicles the long struggle to hold states to account for war crimes. He tells the dramatic story of the twentieth-century jurists, thinkers, and activists who redefined the norms of international law and justice, and inspired a worldwide movement to check the impunity of states. At the end of the nineteenth century, no rules constrained when states could engage in war. Douglas argues that an initial breakthrough occurred after World War I, when the victors sought to put the German kaiser on trial for crimes against “international morality and the sanctity of treatises,” but the monarch...