JERUSALEM — Amid the horrors of the Holocaust, the atrocities perpetrated by a few brutal women have always stood out, like aberrations of nature.

There were notorious camp guards like Ilse Koch and Irma Grese. And lesser known killers like Erna Petri, the wife of an SS officer and a mother who was convicted of shooting to death six Jewish children in Nazi-occupied Poland; or Johanna Altvater Zelle, a German secretary accused of child murder in the Volodymyr-Volynskyy ghetto in Nazi-occupied Ukraine.

The Nazi killing machine was undoubtedly a male-dominated affair. But according to new research, the participation of German women in the genocide, as perpetrators, accomplices or passive witnesses, was far greater than previously thought.

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,” 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.

Lower’s findings shed new light on the Holocaust from a gender perspective, according to experts, and have further underlined the importance of the role of the lower echelons in the Nazi killing apparatus.

“In the dominant literature on perpetrators, you won’t find women mentioned,” said Dan Michman, the chief historian at Yad Vashem, the Holocaust Martyrs’ and Heroes’ Remembrance Authority in Jerusalem.

Lower, 45, presented her work for the first time at this summer’s workshop at Yad Vashem’s International Institute for Holocaust Research. She has been trying to decipher what motivated these women to commit such crimes.

“They challenge so deeply our notion” of what constitutes normal female behavior, she said. But the Nazi system, she added, “turned everything on its head.”

Lower said she worked for many years at the Holocaust Memorial Museum in Washington and is now teaching and researching at Ludwig-Maximilians-Universitat in Munich.

The German women in the eastern territories included nurses, teachers and welfare workers. Women ran the storehouses of belongings taken from Jews. Local Germans were recruited to work as interpreters. Then there were the wives of regional officials, and their secretaries, some from their staffs back home. For women from working-class families or farms in Germany, the occupied zones offered an attractive opportunity to advance themselves, Lower said.

There were up to 5,000 female guards in the concentration camps, making up about 10 percent of the personnel. Grese was hanged at the age of 21 for war crimes committed in Auschwitz and Bergen-Belsen; Koch was convicted of participating in murders at Buchenwald. Petri was tried in East Germany and served a life sentence.

Altvater Zelle went to Ukraine as a 22-year-old single woman and became the secretary of a district commissar, Wilhelm Westerheide. Survivors remembered her as the notorious Fraulein Hanna, and accused her, among other things, of smashing a toddler’s head against a ghetto wall and of throwing children to their deaths from the window of a makeshift hospital.

In Westerheide’s region, about 20,000 Jews were wiped out. He and his loyal secretary were tried twice in West Germany, in the late 1970s and early 1980s. They were acquitted both times because of contradictions that arose in the testimonies of witnesses gathered over 20 years, the former chief prosecutor in the case told Lower.

One survivor, Moses Messer, said he saw the woman he knew as Fraulein Hanna smashing the toddler to death against the wall. He told lawyers in Haifa, Israel, in the early 1960s: “Such sadism from a woman I have never seen. I will never forget this scene.”