structural:expansion, structural:summarization
Genocide, concentration camps, and slave labour

Nazi Germany, under the dictatorship of Adolf Hitler, was responsible for murdering about 6 million Jews in what is now known as the Holocaust. They also murdered an additional 4 million others who were deemed " unworthy of life " (including the disabled and mentally ill, Soviet prisoners of war, Romani, homosexuals, Freemasons, and Jehovah's Witnesses) as part of a program of deliberate extermination, in effect becoming a " genocidal state". Soviet POWs were kept in especially unbearable conditions, and 3.6 million Soviet POWs out of 5.7 million died in Nazi camps during the war. In addition to concentration camps, death camps were created in Nazi Germany to exterminate people on an industrial scale. Nazi Germany extensively used forced labourers; about 12 million Europeans from German-occupied countries were abducted and used as a slave work force in German industry, agriculture and war economy.

The Soviet Gulag became a de facto system of deadly camps during 1942–43, when wartime privation and hunger caused numerous deaths of inmates, including foreign citizens of Poland and other countries occupied in 1939–40 by the Soviet Union, as well as Axis POWs. By the end of the war, most Soviet POWs liberated from Nazi camps and many repatriated civilians were detained in special filtration camps where they were subjected to NKVD evaluation, and 226,127 were sent to the Gulag as real or perceived Nazi collaborators.

Japanese prisoner-of-war camps, many of which were used as labour camps, also had high death rates. The International Military Tribunal for the Far East found the death rate of Western prisoners was 27 percent (for American POWs, 37 percent), seven times that of POWs under the Germans and Italians. While 37,583 prisoners from the UK, 28,500 from the Netherlands, and 14,473 from the United States were released after the surrender of Japan, the number of Chinese released was only 56.

At least five million Chinese civilians from northern China and Manchukuo were enslaved between 1935 and 1941 by the East Asia Development Board, or Kōain, for work in mines and war industries. After 1942, the number reached 10 million. In Java, between 4 and 10 million rōmusha (Japanese: "manual labourers"), were forced to work by the Japanese military. About 270,000 of these Javanese labourers were sent to other Japanese-held areas in Southeast Asia, and only 52,000 were repatriated to Java.