The Partisans were organized on the initiative of Tito following the Axis invasion of Yugoslavia in April 1941, and began an active guerrilla campaign against occupying forces after Germany invaded the Soviet Union in June. A large-scale uprising was launched in July, later joined by Draža Mihailović's Chetniks, which led to the creation of the short-lived Republic of Užice. The Axis mounted a series of offensives in response but failed to completely destroy the highly mobile Partisans and their leadership. By late 1943 the Allies had shifted their support from Mihailović to Tito as the extent of Chetnik collaboration became evident, and the Partisans received official recognition at the Tehran Conference. In Autumn 1944, the Partisans and the Soviet Red Army liberated Belgrade following the Belgrade Offensive. By the end of the war, the Partisans had gained control of the entire country as well as Trieste and Carinthia. After the war, the Partisans were reorganized into the regular armed force of the newly established Federal People's Republic of Yugoslavia.