To concentrate and monitor the Jewish population as well as to facilitate later deportation of the Jews, the Germans and their collaborators created ghettos, transit camps, and forced-labor camps for Jews during the war years. The German authorities also established numerous forced-labor camps, both in the so-called Greater German Reich and in German-occupied territory, for non-Jews whose labor the Germans sought to exploit.
But, in May 1944, a railroad spur line was built right into the camp to accelerate and simplify the handling of the tens of thousands of Hungarian and other Jews deported in the spring and summer of 1944. From then to November 1944, when all the other death camps had been abandoned, Birkenau surpassed all previous records for mass killing. The Hungarian deportations and the liquidation of the remaining Polish ghettos, such as Lodz, resulted in the gassing of 585,000 Jews. This period made Auschwitz-Birkenau into the most notorious killing site of all time.
Up to this point, Auschwitz accounted for only 11 percent of the victims of the 'Final Solution'. However, in August 1942, planning began for the construction of four large-scale gassing facilities. It appears from the plans that the first two gas chambers were adapted from mortuaries which, with the huge crematoria attached to them, were initially intended to cope with mortalities amongst the slave labor force in the camp, now approaching 100,000 and subject to a horrifying death rate. But from the autumn of 1942, it seems clear that the SS planners and civilian contractors were intending to build a mass-murder plant.
Once the strategic Schwerpunkt had been identified, the attack could commence, using the concept of Kesselschlacht (“cauldron battle”). A frontal attack would immobilize the enemy while forces on the flanks would execute a double envelopment, forming a pocket called a Kessel (“cauldron”) around the enemy. Once surrounded, the opposing army, demoralized and with no chance of escape, would face the choice of annihilation or surrender.