In late 1941 Soviet forces invaded Iran in coordination with British Army under an operation known as Anglo-Soviet invasion of Iran. Their forces broke through the border and moved from the Azerbaijan SSR into Iranian Azerbaijan. Reza Shah was forced by the invading British to abdicate in favor of his son Mohammad Reza Pahlavi who replaced his father as Shah on the throne on 16 September 1941. At the aftermath of a four-year-long tumultuous period the Azerbaijan People's Government, a Soviet puppet state, was established in Tabriz, perhaps through direct involvement of the Soviet leadership. This government autonomously ruled the province from November 1945 to November 1946. However, the Soviet soon realized their idea was premature, the mass of the population did not support separatism; under largely Western pressure, the Soviet troops withdrew in 1946, which resulted in the quick collapse of the Azerbaijan People's Government.