Birkenau was the largest of the more than 40 camps and sub-camps that made up the Auschwitz complex. During its three years of operation, it had a range of functions. When construction began in October 1941, it was supposed to be a camp for 125 thousand prisoners of war. It opened as a branch of Auschwitz in March 1942, and served at the same time as a center for the extermination of the Jews. In its final phase, from 1944, it also became a place where prisoners were concentrated before being transferred to labor in German industry in the depths of the Third Reich.
The initial mention of the idea of founding a camp in Brzezinka, a village near Auschwitz concentration camp, is connected with Heinrich Himmler’s first inspection of Auschwitz on March 1, 1941. The former Auschwitz commandant, Rudolf Höss, noted in his autobiography that Himmler issued a range of decrees during this visit about expanding the existing camp and employing the prisoners. One of the newly planned objects that Himmler listed on this occasion was a “camp for 100 thousand POWs.” There are however no documents from that period which would support the version given by Rudolf Höss.
The first plans for the camp from autumn 1941 envisioned an initial capacity of 100 to 125 thousand prisoners. This concept underwent changes several times in 1942. The revised plans called for a doubling of capacity, to 200 thousand. The camp would be divided into four parts, often referred to as construction segments (Bauabschnitte), designated by roman numerals. The first segment was planned for 20 thousand prisoners, and the other three for 60 thousand each. The whole camp would cover an area of 175 acres.
The decision was made in 1941 to locate mass extermination facilities adjacent to the camp that was under construction in Birkenau—gas chambers for the mass killing of Jews brought to Birkenau as part of the Third Reich leadership’s plans for the complete extermination of the Jews of Europe. These gas chambers went into operation the following year.