In 1925, Reza Khan, a former Brigadier-General of the Persian Cossack Brigade, deposed the Qajar dynasty and declared himself king (shah), adopting the dynastic name of Pahlavi, which recalls the Middle Persian language of the Sasanian Empire. By the mid-1930s, Rezā Shāh’s strong secular rule caused dissatisfaction among some groups, particularly the clergy, who opposed his reforms, but the middle and upper-middle class of Iran liked what Rezā Shāh did. In 1935, Rezā Shāh issued a decree asking foreign delegates to use the term Iran in formal correspondence, in accordance with the fact that “Persia” was a term used by Western peoples for the country called “Iran” in Persian. His successor, Mohammad Reza Pahlavi, announced in 1959 that both Persia and Iran were acceptable and could be used interchangeably.

Reza Shah tried to avoid involvement with the UK and the Soviet Union. Though many of his development projects required foreign technical expertise, he avoided awarding contracts to British and Soviet companies because of dissatisfaction during the Qajar Dynasty between Persia, the UK, and the Soviets. Although the UK, through its ownership of the Anglo-Iranian Oil Company, controlled all of Iran’s oil resources, Reza Shah preferred to obtain technical assistance from Germany, France, Italy and other European countries. This created problems for Iran after 1939, when Germany and Britain became enemies in World War II. Reza Shah proclaimed Iran as a neutral country, but Britain insisted that German engineers and technicians in Iran were spies with missions to sabotage British oil facilities in southwestern Iran. Britain demanded that Iran expel all German citizens, but Rezā Shāh refused, claiming this would adversely affect his development projects. This led to the Occupation of Iran by the Allies. Reza Shah was forced to abdicate and was sent to exile.

Mohammad Reza Pahlavi replaced his father on the throne on 16 September 1941. He wanted to continue the reform policies of his father, but a contest for control of the government soon erupted between him and an older professional politician, the nationalistic Mohammad Mosaddegh.

On 13 September 1943, the Allies reassured the Iranians that all foreign troops would leave by 2 March 1946. At the time, the Tudeh Party of Iran, a communist party that was already influential and had parliamentary representation, was becoming increasingly militant, especially in the North. This promoted actions from the side of the government, including attempts of the Iranian armed forces to restore order in the Northern provinces. While the Tudeh headquarters in Tehran were occupied and the Isfahan branch crushed, the Soviet troops present in the Northern parts of the country prevented the Iranian forces from entering. Thus, by November 1945 Azerbaijan had become an autonomous state helped by the Tudeh party. This pro-Soviet nominal-government fell by November 1946, after support from the United States for Iran to reclaim the regions that declared themselves autonomous.

In 1951, the Majlis (the Parliament of Iran) named Mohammad Mossadegh as new prime minister by a vote of 79–12, who shortly after nationalized the British-owned oil industry (see Abadan Crisis). Mossadegh was opposed by the Shah who feared a resulting oil embargo imposed by the West would leave Iran in economic ruin. The Shah fled Iran but returned when the United Kingdom and the United States staged a coup against Mossadegh in August 1953 (see Operation Ajax). Mossadegh was then arrested by pro-Shah army forces.

Major plans to build Iran’s infrastructure were undertaken, a new middle class began flourishing and in less than two decades Iran became the indisputable major economic and military power of the Middle East.

By the mid-1970s, relying on increased oil revenues, Mohammad Reza began a series of even more ambitious and bolder plans for the progress of his country and the march toward the “White Revolution”. But his socioeconomic advances increasingly irritated the clergy. Islamic leaders, particularly the exiled cleric Ayatollah Khomeini, were able to focus this discontent with an ideology tied to Islamic principles that called for the overthrow of the Shah and the return to Islamic traditions, called the Islamic revolution. The Pahlavi regime collapsed following widespread uprisings in 1978 and 1979.

Mohammad Reza fled the country, seeking medical treatment in Egypt, Mexico, the United States, and Panama, and finally resettled with his family in Egypt as a guest of Anwar Sadat.

Pahlavi Kings

• Reza Shah (1925-1941)
• Mohammad Reza Shah (1941-1979)