The researcher, Wendy Lower, an American historian now living in Munich, has drawn attention to the number of seemingly ordinary German women who willingly went out to the Nazi-occupied eastern territories as part of the war effort, to areas where genocide was openly occurring.

“Thousands would be a conservative estimate,” Ms. Lower said in an interview in Jerusalem last week.

While most did not bloody their own hands, the acts of those who did seemed all the more perverse because they operated outside the concentration camp system, on their own initiative…

Ms. Petri was married to an SS officer who ran an agricultural estate, complete with a colonial-style manor house and slave laborers, in Galicia, in occupied Poland. She later confessed to having murdered six Jewish children, aged 6 to 12. She came across them while out riding in her carriage. She was the mother of two young children, and was 25 at the time. Near naked, the Jewish children had apparently escaped from a railroad car bound for the Sobibor camp. She took them home, fed them, then led them into the woods and shot them one by one.