Auschwitz death camp was in operation from May 1940 until its liberation by Soviet forces in January 1945. It is estimated that 2.1 to 2.5 million people were killed in the gas chambers during that time, of whom 2 million were Jews and the remainder were Poles, Gypsies and Soviet POWs. But this estimate is considered by historians to be strictly a minimum, because the total number of deaths at Auschwitz and its sister camp Birkenau can never really be known.