The 1953 Iranian coup d'état (known in Iran as the 28 Mordad coup) saw the overthrow of the democratically elected government of Iranian Prime Minister Mohammad Mosaddegh on 19 August 1953 and the installation of a military government. This coup was orchestrated by the intelligence agencies of the United Kingdom and the United States under the name TPAJAX Project. The result of this event was that under the direct orders of Mohammad-Rezā Shāh Pahlavi, the administration of the country got out of the hands of the parliament to find itself under the supervision of an illegitimate government. The establishment of this power was under major support of its foreign allies until its overthrow in 1979.
In 1951, Iran's oil industry was nationalized with near-unanimous support of Iran's parliament in a bill introduced by Mossadegh, who led the oil commission of the parliament. Iran's oil had been controlled by the British-owned Anglo-Iranian Oil Company (AIOC) under license, and was only a source of little revenue for the country. Popular discontent with the AIOC began in the late 1940s as a large segment of Iran's public and a number of politicians saw the company as exploitative and a vestige of British imperialism. Despite Mosaddegh's popular support, Britain was unwilling to negotiate its single most valuable foreign asset, and instigated a worldwide boycott of Iranian oil to pressure Iran economically. Initially, Britain mobilized its military to seize control of the Abadan oil refinery, the world's largest, but Prime Minister Clement Attlee opted instead to tighten the economic boycott while using Iranian agents to undermine Mosaddegh's government. With a change to more conservative governments in both Britain and the United States, Churchill and the U.S. Eisenhower administration decided to overthrow Iran's government though the previous U.S. Truman administration had opposed a coup.
Britain and the U.S. selected Fazlollah Zahedi to be the prime minister of a military government that was to replace Mosaddegh's government. Subsequently, a royal decree dismissing Mosaddegh and appointing Zahedi was drawn up by the coup plotters and signed by the Shah. The Central Intelligence Agency had successfully pressured the weak monarch to participate in the coup, while bribing street thugs, clergy, politicians and Iranian army officers to take part in a propaganda campaign against Mosaddegh and his government. At first, the coup appeared to be a failure when on the night of 15–16 August, Imperial Guard Colonel Nematollah Nassiri was arrested while attempting to arrest Mosaddegh. With this arrest, the plan was put in action differently. After the Shah getting away from the country, on 19 August, a pro-Shah mob paid by the CIA marched on Mosaddegh's residence. According to the CIA's declassified documents and records, some of the most feared mobsters in Tehran were hired by the CIA to stage pro-Shah riots on 19 August. Other CIA-paid men were brought into Tehran in buses and trucks, and took over the streets of the city. Many people were killed during and as a direct result of the conflict. Mosaddegh was arrested, tried and convicted of treason by the Shah's military court. On 21 December 1953, he was sentenced to three years in jail, then placed under house arrest in Ahmad Abad for the remainder of his life.
After the coup, the tangible benefits the United States reaped from overthrowing Iran's elected government included a share of Iran's oil wealth as well as resolute prevention of the slim possibility that the Iranian government might align itself with the Soviet Union, although the latter motivation still produces controversy among historians. Mohammad-Reza Pahlavi ruled as an authoritarian monarch for the next 26 years, while depending on the support of the powers that had supported him in the coup until he was overthrown in a popular revolt in 1979.