This book is a study of the reports of the Einsatzgruppen, the four SS extermination squads that followed in the wake of the German attack on the Soviet Union on 22 June 1941. It was the Einsatzgruppen that began the systematic massacre of Jews, communist officials, and other "undesirables" in the territories overrun by the Germans. More than one million people, mostly Jews, ultimately perished at the hands of the Einsatzgruppen Kommandos. This horrific destruction was recorded in great detail in the top-secret reports of the Einsatzgruppen, which were compiled in Berlin based on material sent in from the east by the Kommandos. No other documents discovered offer such an extensive and precise day-by-day account of mass killings written while these killings were actually taking place. The killings are the principal focus of this book and are analyzed in the central chapters from several perspectives. Included among these are descriptions of the main features of the reports and the various stages in their compilation, examples and methodology of presentation of the killings, and comparisons of reporting procedures and totals of victims shot by each of the four Einsatzgruppen. The study begins by noting the post-war discovery of the reports and then assumes a roughly chronological sequence in its overall treatment. An outline of the major National Socialist agencies and general reporting practices before the war is followed by the events of the war as reflected in the reports. Then the postwar "life" of the reports is examined with particular reference to their use as legal evidence at Nuremberg as well as a consideration of their reliability as historical source material. In addition to the descriptive and comparative information mentioned above, this study places the reports within the historical context of the reporting practices, complex rivalry, and self-aggrandizement of the leading German agencies. Certain questions of concern to historians are also explored in light of the reports. These include: the reactions of the indigenous eastern population to the German presence; the active collaboration of members of the local population and the German army in the killing operations; and the role of the Einsatzgruppen in relation to the current intentionalist-functionalist debate concerning National Socialism and Hitler's attempt to exterminate the Jews. Among the wealth of Nazi material that survived the war, the Einsatzgruppen reports occupy a significant place. As a virtually complete and self-contained body of documents, the reports are a fertile source for historians of the Third Reich and the Holocaust. In what they reveal directly about the destruction and what they tell us indirectly about the men who perpetrated this destruction, the reports provide us with important insight into the process of mass murder.