Upon the dethronement of Reza Shah in September 1941, Soviet forces took control of Iranian Azerbaijan and helped to set up the Azerbaijan People's Government, a client state under the leadership of Sayyid Jafar Pishevari backed by Soviet Azerbaijan. The Soviet military presence in Iranian Azerbaijan was mainly aimed at securing the Allied supply route during World War II. Concerned with the continued Soviet presence after World War II, the United States and Britain pressured the Soviets to withdraw by late 1946. Immediately thereafter, the Iranian government regained control of Iranian Azerbaijan.