The ancient nation of Iran, historically known to the West as Persia and once a major empire in its own right, has been overrun frequently and has had its territory altered throughout the centuries. Invaded by Arabs, Seljuk Turks, Mongols, and others--and often caught up in the affairs of larger powers--Iran has always reasserted its national identity and has developed as a distinct political and cultural entity.

Archeological findings have placed knowledge of Iranian prehistory at middle paleolithic times (100,000 years ago). The earliest sedentary cultures date from 18,000-14,000 years ago. The sixth millennium B.C. saw a fairly sophisticated agricultural society and proto-urban population centers. Many dynasties have ruled Iran, the first of which was the Achaemenid (559-330 B.C.), a dynasty founded by Cyrus the Great. After the Hellenistic period (300-250 B.C.) came the Parthian (250 B.C.-226 A.D.) and the Sassanian (226-651) dynasties.

The seventh century Arab-Muslim conquest of Iran was followed by conquests by the Seljuk Turks, the Mongols, and Tamerlane. Iran underwent a revival under the Safavid dynasty (1502-1736), the most prominent figure of which was Shah Abbas. The conqueror Nadir Shah and his successors were followed by the Zand dynasty, founded by Karim Kahn, and later the Qajar (1795-1925) and the Pahlavi dynasties (1925-1979).

Modern Iranian history began with a nationalist uprising against the Shah (who remained in power) in 1905, the granting of a limited constitution in 1906, and the discovery of oil in 1908. In 1921, Reza Khan, an Iranian officer of the Persian Cossack Brigade, seized control of the government. In 1925, he made himself Shah, ruling as Reza Shah Pahlavi for almost 16 years and installing the new Pahlavi dynasty.

Under his reign, Iran began to modernize and to secularize politics, and the central government reasserted its authority over the tribes and provinces. In September 1941, following the Allies' (United Kingdom-Soviet Union) occupation of western Iran, Reza Shah was forced to abdicate. His son, Mohammad Reza Pahlavi, became Shah and ruled until 1979.

During World War II, Iran was a vital link in the Allied supply line for lend-lease supplies to the Soviet Union. After the war, Soviet troops stationed in northwestern Iran not only refused to withdraw but backed revolts that established short-lived, pro-Soviet separatist regimes in the northern regions of Azerbaijan and Kurdistan. These were ended in 1946. The Azerbaijan revolt crumbled after U.S. and UN pressure forced a Soviet withdrawal and Iranian forces suppressed the Kurdish revolt.

In 1951, Premier Mohammed Mossadeq, a militant nationalist, forced the parliament to nationalize the British-owned oil industry. Mossadeq was opposed by the Shah and was removed, but he quickly returned to power. The Shah fled Iran but returned when supporters staged a coup against Mossadeq in August 1953. Mossadeq was then arrested by pro-Shah army forces. In 1961, Iran initiated a series of economic, social, and administrative reforms that became known as the Shah's White Revolution. The core of this program was land reform. Modernization and economic growth proceeded at an unprecedented rate, fueled by Iran's vast petroleum reserves, the third-largest in the world.

In 1978, domestic turmoil swept the country as a result of religious and political opposition to the Shah's rule and programs--especially SAVAK, the hated internal security and intelligence service. In January 1979, the Shah left Iran; he died abroad several years after.

On February 1, 1979, exiled religious leader Ayatollah Ruhollah Khomeini returned from France to direct a revolution resulting in a new, theocratic republic guided by Islamic principles. Back in Iran after 15 years in exile in Turkey, Iraq, and France, he became Iran's national religious leader. Following Khomeini's death on June 3, 1989, the Assembly of Experts--an elected body of senior clerics--chose the outgoing president of the republic, Ali Khamenei, to be his successor as national religious leader in what proved to be a smooth transition.

In August 1989, Ali Akbar Hashemi-Rafsanjani, the speaker of the Majles, was elected President by an overwhelming majority. He was re-elected June 1993, with a more modest majority; some Western observers attributed the reduced voter turnout to disenchantment with the deteriorating economy.

Following the election of reformer Hojjat ol-Eslam Mohammad KHATAMI as president in 1997 and a reformist Majles (legislature) in 2000, a campaign to foster political reform in response to popular dissatisfaction was initiated. The movement floundered as conservative politicians, supported by the Supreme Leader, unelected institutions of authority like the Council of Guardians, and the security services reversed and blocked reform measures while increasing security repression. Starting with nationwide municipal elections in 2003 and continuing through Majles elections in 2004, conservatives reestablished control over Iran's elected government institutions, which culminated with the August 2005 inauguration of hardliner Mahmud AHMADI-NEJAD as president. His controversial reelection in June 2009 sparked nationwide protests over allegations of electoral fraud, but the protests were quickly suppressed. Deteriorating economic conditions due primarily to government mismanagement and international sanctions prompted at least two major economically based protests in July and October 2012, but Iran's internal security situation remained stable. President AHMADI-NEJAD's independent streak angered regime establishment figures, including the Supreme Leader, leading to conservative opposition to his agenda for the last year of his presidency, and an alienation of his political supporters. In June 2013 Iranians elected a centrist cleric Dr. Hasan Fereidun RUHANI to the presidency. A longtime senior member in the regime, he made promises of reforming society and Iran's foreign policy. In July 2015, Iran and the five permanent members, plus Germany (P5+1) signed the JCPOA under which Iran agreed to restrictions on its nuclear program in exchange for sanctions relief; however, the US reimposed sanctions in 2018 dealing a blow to RUHANI's legacy and the Iranian economy. Negotiations to restore the deal started in 2021 and are ongoing. Iran held elections in February 2020 for the Majles and the president in June 2021, resulting in a hardline and conservative monopoly across the regime's elected and unelected institutions. President Ebrahim RAISI is a hardline cleric with a decades-long career in Iran's judiciary and has had limited foreign policy and economic experience.