The twentieth century was among the bloodiest in the history of humanity. Untold millions were slaughtered. How people are enrolled in the service of evil is a question that continues to bedevil. In this trenchant book, Abram de Swaan offers a taxonomy of mass violence that focuses on the rank-and-file perpetrators, examining how murderous regimes recruit them and create what De Swaan calls the "killing compartments” that make possible the worst abominations without apparent moral misgiving, without a sense of personal responsibility, and, above all, without pity.

De Swaan wonders where extreme violence comes from and where it goes—seemingly without a trace—when the wild and barbaric gore is over. And what about the perpetrators themselves? Are they merely and only the product of external circumstance? Or is there something in their makeup that disposes them to become mass murderers? Drawing on a wide range of disciplines, including sociology, anthropology, political science, history, and psychology, De Swaan sheds new light on an urgent and intractable pathology that continues to poison peoples all over the world.