Almost a quarter of the Jews killed in the Holocaust were murdered during 100 days in 1942, making it the time frame with the highest killing pace in the 20th century, according to a new Israeli study published on Wednesday.

The mass murder between August and October 1942 included Jews exterminated in Auschwitz, in Ukraine and as part of “Operation Reinhard,” an intense mass-slaughter campaign carried out by the Nazis between March 1942 and November 1943 in death camps Belzec, Treblinka and Sobibor. The operation itself killed some 1.7 million Polish Jews.

That rate during that operation has been “poorly quantified in the past,” said Lewi Stone, a professor at Tel Aviv University, who published his study in the Science Advances academic journal. He mentioned that most records of the killings were destroyed by the Nazis.

The estimated average of 15,000 deaths daily during the “extreme phase of hyper-intense killing” is nearly three times greater than previous approximations.

Stone said that the murder pace declined in November 1942 due to “relatively few Jews left” in Nazi-controlled places in and around Poland, “so the rate of the killing likely subsided because of the difficulty of rounding up victims.”

This study implies that those three months consisted of a higher killing rate than the 1994 Rwandan genocide, which had been widely seen as the quickest murderous campaign in the 20th century, with some 800,000 people massacred over 100 days.

“Historians, social scientists, policy-makers and journalists have consistently relied on inaccurate assessments that greatly underestimated the Holocaust kill rate during ‘Operation Reinhard,’ ” wrote Stone.

“It’s not a big [innovation],” Holocaust scholar Deborah Lipstadt told JNS. “We always knew that that period was the height of the killing. With the exception of Hungarian Jews – admittedly not a small number — most Jews murdered by the Nazis were dead by the end (and even earlier) of 1943.”