Auschwitz concentration camp was a complex of 48 concentration and extermination camps built and operated by Nazi Germany in occupied Poland during World War II. It consisted of Auschwitz I (the original concentration camp), Auschwitz II–Birkenau (a combined concentration/extermination camp), Auschwitz III–Monowitz (a labor camp to staff an IG Farbenfactory), and dozens more subcamps.
Auschwitz I was first constructed to hold Polish political prisoners, who began to arrive in May 1940. The first extermination of prisoners took place in September 1941. Auschwitz II–Birkenau went on to become a major site of the Nazis' Final Solution to the Jewish Question during the Holocaust. From early 1942 until late 1944, transport trains delivered Jews to the camp's gas chambers from all over German-occupied Europe, where they were killed en masse with the cyanide-based poison Zyklon B, originally developed to be used as a pesticide. An estimated 1.3 million people were sent to the camp, of whom at least 1.1 million died. Around 90 percent of those were Jews; approximately one in six Jews killed in the Holocaust died at the camp. Others deported to Auschwitz included 150,000 Poles, 23,000 Romani and Sinti, 15,000 Soviet prisoners of war, 400 Jehovah's Witnesses, and tens of thousands of others of diverse nationalities, including an unknown number of homosexuals. Many of those not killed in the gas chambers died of starvation, forced labor, infectious diseases, individual executions, and medical experiments.
In the course of the war, the camp was staffed by 7,000 members of the German Schutzstaffel (SS), approximately 12 percent of whom were later convicted of war crimes. Some, including camp commandant Rudolf Höss, were executed. The Allied Powers did not act on early reports of atrocities at the camp, and their failure to bomb the camp or its railways remains controversial. At least 802 prisoners attempted to escape from Auschwitz, 144 successfully, and on 7 October 1944 two Sonderkommando units, consisting of prisoners assigned to staff the gas chambers, launched a brief, unsuccessful uprising.
As Soviet troops approached Auschwitz in January 1945, most of its population was sent west on a death march. The prisoners remaining at the camp were liberated on 27 January 1945, a day now commemorated as International Holocaust Remembrance Day. In the following decades, survivors such as Primo Levi, Viktor Frankl, and Elie Wiesel wrote memoirs of their experiences in Auschwitz, and the camp became a dominant symbol of the Holocaust. In 1947 Poland founded the Auschwitz-Birkenau State Museum on the site of Auschwitz I and II, and in 1979 it was named a World Heritage Site by UNESCO.