This book, the first global history of genocide and extermination from ancient times, examines outbreaks of mass violence from the classical era to the present, focusing on worldwide colonial exterminations and twentieth-century case studies including the Armenian genocide, the Nazi Holocaust, Stalin's mass murders, and the Cambodian and Rwandan genocides. Connections, patterns, and features are identified that in nearly every case gave early warning of the catastrophe to come. Racism or religious prejudice, territorial expansionism, and cults of antiquity and agrarianism are ideologies that have motivated perpetrators of mass killings in the past, and persist even in our new century. The author urges that we heed the rich historical evidence with its telltale signs for predicting and preventing future genocides.