Auschwitz, also known as Auschwitz-Birkenau, opened in 1940 and was the largest of the Nazi concentration and death camps. Located in southern Poland, Auschwitz initially served as a detention center for political prisoners. However, it evolved into a network of camps where Jewish people and other perceived enemies of the Nazi state were exterminated, often in gas chambers, or used as slave labor. Some prisoners were also subjected to barbaric medical experiments led by Josef Mengele (1911-79). During World War II (1939-45), more than 1 million people, by some accounts, lost their lives at Auschwitz. In January 1945, with the Soviet army approaching, Nazi officials ordered the camp abandoned and sent an estimated 60,000 prisoners on a forced march to other locations. When the Soviets entered Auschwitz, they found thousands of emaciated detainees and piles of corpses left behind.