The Pahlavis came to power after Ahmad Shah Qajar, the last Qajar ruler of Iran, proved unable to stop British and Soviet encroachment on Iranian sovereignty, had his position extremely weakened by a military coup, and was removed from power by the parliament while in France. The Iranian parliament, known as the Majlis, convening as a Constituent Assembly on 12 December 1925, deposed the young Ahmad Shah Qajar, and declared Reza Khan the new King (Shah) of Imperial State of Persia. In 1935, Reza Shah asked foreign delegates to use the endonymIran in formal correspondence and the official name the Imperial State of Iran was adopted.
Following the coup d'état in 1953 supported by United Kingdom and the United States, Mohammad Reza Pahlavi's rule became more autocratic and was aligned with the Western Bloc during the Cold War . Faced with growing public discontent and popular rebellion throughout 1978 and after declaring surrender and officially resigning , the second Pahlavi went into exile with his family in January 1979, sparking a series of events that quickly led to the end of the state and the beginning of the Islamic Republic of Iran on 11 February 1979.