Groups of career soldiers and socialist and nationalist political activists made up the Polish underground in 1940-1941. A merger in 1942 resulted in a single organization that identified with and called itself the Home Army (AK).
Its leader was Col. Juliusz Gilewicz, a prisoner who was shot in a mass execution on October 10, 1943. The camp Home Army corresponded to the large nationwide organization of the same name that took orders from the Polish government-in-exile in London. There were also leftist groups in the camp, with Polish Socialist Party (PPS) members as the backbone.
As the Auschwitz prisoner population changed, prisoners of other ethnic backgrounds, mostly Jews, joined the resistance movement and gave it a more diverse nature. Some groups were organized on an ethnic basis, and others were mixed. Many such groups arose at the turn of 1942/1943, not only Jewish but also Austro-German, Czech, French, Russian, and Yugoslavian. Most were leftist. In 1943, some of them joined with Polish leftists and socialists to create an international organization under the name Kampfgruppe Auschwitz (Auschwitz Combat Group). In 1944, the Home Army and Kampfgruppe Auschwitz set up a joint Auschwitz Military Council, tasked with preparing an uprising in the camp.