From the first months of the war, Piotrków was a centre for underground resistance. From the spring of 1940, it was the seat of the district headquarters of the Armia Krajowa, or Home Army. In the summer of 1944, the 25th Infantry Regiment of the Home Army was formed in the district; it was the largest military unit of the Łódź Voivodeship, and fought against the Germans until November 1944. In the city and district, there were also other partisan groups: the Military Troops (connected with the Polish Socialist Party), People's Guard and People's Army (Polish Workers' Party), Peasants' Battalions (Polish People's Party), the National Military Organization and the National Armed Forces (National Party). After the fall of the Warsaw Uprising, the headquarters of the Polish Red Cross was temporarily located in the local Royal Castle from October 1944 to January 1945.