extermination camps:

A mother and her children on their way to the gas chambers.After World War II started in 1939, some concentration camps were transformed into sites for carrying out genocide. These camps, all in occupied Poland, are sometimes called “death factories.” A total of 3.5 million Jews were killed in the gas chambers of the extermination camps, as well as tens of thousands of Gypsies, homosexuals, political prisoners, Jehovah’s Witnesses and Soviet prisoners of war. Prisoners managed to organize uprisings in a number of camps.