A recently translated book about the Holocaust has claimed that Italian citizens played a crucial and enthusiastic role in the Nazi genocide during World War II.

Historian Simon Levis Sullam’s book, The Italian Executioners: The Genocide of the Jews of Italy, was published in 2015 but only translated into English this year. In the book, Sullam provides what he calls a “historiographical counterblast” to shed light on the complicity of Italians in one of the worst crimes in human history, The Times of Israel said.

Sullam tracked more than 6,000 Italian Jews who were murdered during the final two years of the war. Most were detained and sent to Nazi concentration camps with the help of anti-Semitic Italian laws.