During the rest of World War II, Iran became a major conduit for British and American aid to the Soviet Union and an avenue through which over 120,000 Polish refugees and Polish Armed Forces fled the Axis advance. At the 1943 Tehran Conference, the Allied "Big Three"—Joseph Stalin, Franklin D. Roosevelt, and Winston Churchill—issued the Tehran Declaration to guarantee the post-war independence and boundaries of Iran. However, at the end of the war, Soviet troops remained in Iran and established two puppet states in north-western Iran, namely the People's Government of Azerbaijan and the Republic of Mahabad. This led to the Iran crisis of 1946, one of the first confrontations of the Cold War, which ended after oil concessions were promised to the USSR and Soviet forces withdrew from Iran proper in May 1946. The two puppet states were soon overthrown and the oil concessions were later revoked.