The specter of genocide, unleashed with a vengeance in the twentieth century, now haunts the globe. For several decades, daily newspapers and nightly television news have regularly featured stories about genocide and other mass violence. Killing continues almost under our noses. New and horrific mass crimes and violence seem only around the corner. For these reasons and more, scholars from many disciplines and writers of all kinds have immersed themselves in the tasks of researching past and ongoing cases of mass murder. The terrorist attacks of September 2001 on the World Trade Center in New York will certainly stimulate more such research.

Our sense of the multiplying violence around us is reinforced by the plethora of new evidence about past atrocities, partly from the post–Cold War opening of formerly secret Soviet archives, but also elsewhere. The discovery of the chilling security archives of the Khmer Rouge, revelations of Italian wartime crimes against humanity in the Balkans and Africa, new evidence of French official crimes during the Algerian War in the memoirs of General Paul Aussaresses, and documentation of the Western Hemisphere–wide “Thirty Years' Dirty War” against leftists in Latin America have all brought heretofore hidden mass murders to public attention. Even lost Nazi documents continue to surface, and historians are producing new studies of the Holocaust based on them.