The duly elected prime minister, Mohammed Mossadegh, was unseated by the CIA's "Operation Ajax," in 1953. He was replaced by Mohammed Reza Pahlavi, who was soon reinstated as the traditional Iranian shah. There was an agreement made between Pahlavi and the United States government; Iran would recieve military and economic aid in exchange for a continuous supply of oil to America. The Iranian people soon become enraged because Pahlavi promised them personal freedoms that they did not recieve, causing them to revolt which lead the shah to abdicate his throne in January 1979.
Ayatollah Khomeini became the new ruler soon after the throne was abandoned. Khomeini railed against the American government, calling it "The Great Satan" and "Enemy of Islam." Not long after,  Khomeini was diagonosed with lymphoma. Since the American doctors were much more educated, Khomeini requested that he be treated for his cancer by an American doctor. The Iran people were not happy about this, which caused them to storm the American Embassy in Teheran, Iran.