Once Germany took over Poland in 1939, it created forced-labor camps. Thousands of prisoners died from working conditions, exhaustion, and starvation. After the outbreak of World War II, the number of concentration camps increased exponentially. The number of prisoners of war camps also rose, but after the first years of the war most were converted into concentration camps. Nazis forcibly relocated Jews from ghettos to concentration camps.
Hitler targeted the Jews for a specific reason, which was not just racial. The elimination of the Jews had a unique “status” in Hitler’s master plan. While he certainly killed millions of others (gypsies, communists, homosexuals, etc.) he made exceptions for all these groups. The only group for which no exception was made was the Jews—they all had to die.
During the era of the Holocaust, German authorities also targeted other groups because of their perceived racial and biological inferiority: Roma (Gypsies), people with disabilities, and some of the Slavic peoples (Poles, Russians, and others). Other groups were persecuted on political, ideological, and behavioral grounds, among them Communists, Socialists, Jehovah's Witnesses, and homosexuals.
Josef Mengele (/ˈmɛŋɡələ/; German: [ˈmɛŋələ]; 16 March 1911 – 7 February 1979) was a German Schutzstaffel (SS) officer and physician in Auschwitz concentration camp during World War II. He performed deadly human experiments on prisoners and was a member of the team of doctors who selected victims to be killed in the gas chambers. Arrivals that were judged able to work were admitted into the camp, while those deemed unsuitable for labor were sent to the gas chambers to be killed. With Red Army troops sweeping through Poland, Mengele was transferred 280 kilometers (170 mi) from Auschwitz to the Gross-Rosen concentration camp on 17 January 1945, just ten days before the arrival of the Soviet forces at Auschwitz. After the war, he fled to South America where he evaded capture for the rest of his life.