The post-revolutionary government of Iran has regarded the United States and the United Kingdom as imperialist states, who have a long history of interfering in Iran's internal affairs. In 1907, an Anglo-Russian agreement between Russia and Britain divided Iran into spheres of influence, ignoring, although not terminating, Iran's sovereignty. In 1953, during the Cold War, British intelligence officials and the administration of the U.S. President Dwight D. Eisenhower planned a joint Anglo-American operation to overthrow the elected prime minister, Mohammad Mossadeq. The Eisenhower administration was concerned that Mossadeq's nationalist aspirations could lead to an eventual communist takeover of Iran. The operation was code-named Operation Ajax. At first, the military coup seemed to fail, and Shah Mohammed Reza Pahlavi fled the country. After widespread rioting and with help from the CIA and British intelligence services, Mossadeq was defeated and the Shah returned to power, ensuring support for Western (chiefly British) oil interests and ending the perceived threat of communist expansion. General Fazlollah Zahedi, who led the military coup, became prime minister.