In this pathbreaking interrogation of the last century of American history, Power draws upon her own reporting from the modern killing fields to tell the story of American indifference and American courage in the face of the worst massacres of the 20th century. In this work of social history, Power examines how, since the Holocaust, Americans have very rarely marshalled their might to stop genocide and mass terror. It makes a moral argument for why America must renew its vigilance against genocide.