The wartime resistance movement, and the Armia Krajowa ("Home Army"), fought against German occupation. It was one of the three largest resistance movements of the entire war, and encompassed a range of clandestine activities, which functioned as an underground state complete with degree-awarding universities and a court system. The resistance was loyal to the exiled government and generally resented the idea of a communist Poland; for this reason, in the summer of 1944 it initiated Operation Tempest, of which the Warsaw Uprising that begun on 1 August 1944 is the best known operation.