Book excerpt: This is why, although the process of genocide was proceeding at top speed, some Jews were diverted from the gas chambers and sent to work at Gross-Rosen. Auschwitz-Birkenau was the main provider of inmate slave laborers for the Gross-Rosen armaments, munitions, and other factories owned by giant private enterprises, such as Krupp, J.G. Farben, and Siemens. Jewish inmates were also used in the construction of Hitler's secret headquarters in the local Eulen Mountains and the secret underground tunnels used to store weapons.