Over six million Jews were murdered during the Holocaust, and those who were not killed were either sent to concentration camps or ghettos. When Soviet forces advanced into eastern Poland in 1944 and western Poland in January 1945, they liberated the prisoners of the extermination camps of Majdanek, Auschwitz-Birkenau, and several smaller camps. Later in the spring, the US and British armies liberated survivors of the concentration camps of Bergen-Belsen, Buchenwald, and Dachau.