The period between the two World Wars was characterized by an acceleration of mass violence across the world. Developments in technology, communications, ideology, global political and economic integration, and the organization of society greatly expanded the power and reach of states while radicalizing ideologies of domination and control. Two major 20th-century genocides, the Armenian Genocide in the Ottoman Empire and the Nazi Holocaust of European Jews, are the terrible bookends of this period; they were preceded and informed by colonial genocides, such as the genocide of Herero and Nama peoples in German South West Africa from 1904 -1914, and by ongoing genocidal processes, especially in settler colonies such as the United States, Canada, and Australia, in the renewed Russian empire under the USSR after 1917, and in the expanding Japanese empire between the wars. The essays in this volume examine the dynamics of genocide during this period, when states could draw on new technologies, new identities, and new global ideologies of control to amplify the speed, size, and impact of their destructive impulses towards unwanted populations. The chapters demonstrate the lasting consequences of genocidal processes on the world today, not simply for survivor communities and survivor diasporas, but also on the forms of organizing the world, the concepts of power, and the particular existential crises that we as a species have yet to address and transform.