Dutch resistance groups gathered counterintelligence (information about the Nazis), committed sabotage, and formed communications networks. This helped the Allied forces, beginning in 1944 and continuing until the Netherlands was liberated. About 75% (105,000 out of 140,000) of Dutch Jews were killed in the Holocaust, most of them murdered in Nazi death camps. A number of resistance groups specialized in saving Jewish children. Somewhere between 215 and 500 Dutch Romanis were also killed by the Nazis.