No satisfactory English translation has been found for the German term Einsatzgruppen (EG). An accurate description might be "special extermination groups." Their primary assignment was to kill every Jewish man, woman, or child they could lay their hands on. Romani (pejoratively called "gypsies") were to suffer the same fate. Communist leaders or others suspected of any future threat to Adolf Hitler's conquests would also be targets for annihilation. Security Chief Reinhard Heydrich issued the order on September 21, 1939: "The total measures planned are to be kept strictly secret" (1949, p.120).

In May 1941, with Germany's assault against the Soviet Union imminent, four Einsatz groups were assembled. Each encompassed 500 to 800 men commanded by leading Nazis. The German army provided help and logistic support. On orders from Hitler, the EG were to break all possible civilian resistance behind the fighting front by...