of Yugoslavia and the USSR signed the Treaty of Friendship and Non-Aggression, which did not commit the parties to military assistance in case of aggression. According to Soviet General Pavel Sudoplatov, the Soviet leadership was shocked by an instant defeat of Yugoslavia in April 1941, after Hitler reacted to the coup ″promptly and effectively″. The USSR formally severed relations with Yugoslavia on 8 May 1941, but in practice yet before that. After Germany attacked the Soviet Union on 22 June 1941, the USSR began to assist the military campaign of Communist partisans led by Tito; and from the autumn of 1944 regular Red Army troops directly participated in battles in cooperation with the Partisans, especially in the territories of present-day Serbia. The most notable of these battles in which Soviet soldiers fought in Serbian territories was the Belgrade Offensive. The ROVS′ Department IV (Yugoslavia) was the only regional branch of the Russian All-Military Union that made a decision to side with Germany against the USSR and ROVS participated in forming the Russian Protective Corps () that was established in Serbia in September 1941. The Russian Corps was engaged in guarding important sites and also combating the Communist partisans led by Tito. Socialist Yugoslavia and USSR After the war ended in May 1945, King Peter II was not allowed to return to Yugoslavia; in November 1945 he was formally deposed by Yugoslavia's Communist Constituent Assembly with the state reorganised as a republic and renamed Federal People's Republic of Yugoslavia (FPR Yugoslavia or FPRY; from 1963 Socialist Federal Republic of Yugoslavia, or SFRY). Initially, Yugoslavia's Communist regime under Josip Broz Tito was loyal to Joseph Stalin′s Kremlin. The latter wanted Yugoslavia to become a member of the USSR-led block of Communist countries. However, Tito eventually rejected Stalin's pressure and in 1950s became one of the founders of the Non-Aligned Movement, which was regarded as the third way, neither adhering to the U.S.-led NATO, nor joining the Moscow-dominated Warsaw Pact. As early as on 11 April 1945, the USSR concluded a friendship treaty with Josip Tito, who put signature on behalf of the Regent Council of Yugoslavia. In the first two years following the war, relations between FPRY and the Soviet leadership, which during that period sought to accommodate the USSR's Western allies demands in Europe, were not entirely free of disagreements on a number of issues, such as Yugoslavia's territorial claims to