The Iranian Revolution (AKA the 1979 Revolution or the Islamic Revolution of Iran, concertns surrounding the usurpation of the Pahlavi dynasty under Mohammad Reza Shah Pahlavi, who was supported and encouraged by the United States, and its eventual replacement with an Islamic republic under the Grand Ayatollah Ruhollah Khomeini, the leader of the revolution, supported by various leftist and Islamic organisations and Iranian student movements. While the Soviet Union immediately recognised the new Islamic Republic, it did not actively support the revolution, despite initially making efforts to salvage the Shah’s government.
Demonstrations against the Shah commenced in October 1977, developing into a campaign of civil resistance that was religious based (with secular elements) that intensified in January 1978. Between August and December 1978, strikes and demonstrations paralysed the country. The Shah left Iran for exile on January 16, 1979 as the last Persian monarch, leaving his duties to a regency council and an opposition-based prime minister. The Ayatollah Khomeini was invited back to Iran by the government, and returned to Tehran to be greeted by several million Iranians. The royal reign collapsed shortly after on February 11 when guerrillas and rebel troops overwhelmed troops loyal to the Shah in armed street fighting, and bringing Khomeini to official power. On April 1, 1979, Iran voted by national referendum to become an Islamic Republic, and to approve a new theocratic-republican constitution whereby Khomeini became Supreme Leader of the country, in December 1979.
The revolution lacked many of the customary causes of revolution such as defeat at war, a financial crisis, peasant rebellion or disgruntled military, and as such, it caused surprise throughout the world because it occurred in a nation that was enjoying relatively good material wealth and prosperity. It produced profound change at great speed and was massively popular, resulting in the exile of many Iranians, and replaced a pro-Western semi-absolute monarchy with an anti-Western authoritarian theocracy based on the concept of Guardianship of the Islamic Jurists (or velayat-e faqih). It was a relatively non-violent revolution, and helped to redefine the meaning and practice of modern revolutions (although violence occured in its aftermath).