As early as 6000 BC , communities on the Iranian plateau were carrying on agriculture, raising domestic animals, and producing pottery and polished stone implements. Sites datable to later than 3000 BC are numerous and offer quantities of bronze instruments and painted pottery of the finest types. About 1500 BC , masses of Indo-Europeans, or Aryans, began to cross the plateau of Iran. The Iranian group included Medes, Persians, Parthians, Bactrians, and others. The Medes settled in western Iran (Media) about 900 BC and established their capital at Ecbatana (modern Hamadan); the Persians settled to the south of them (Parsis) around 700 BC . The Median king Cyaxares (625–585 BC ), along with the Chaldeans, destroyed the power of neighboring Assyria. In the area of Parsis, the Achaemenid clan became overlords, and in 550 BC , their leader, Cyrus the Great, revolted against the Medes; forming a union of Medes and Persians, he then drove with armies both into Asia Minor and to the east of the Iranian plateau and established the Achaemenid Empire. Cambyses, Darius, Xerxes I, and Artaxerxes I were notable rulers of this line who penetrated Greece, Egypt, and beyond the Oxus. The Achaemenid power was centered at Susa and Persepolis; the ruined site of the latter is impressive even today. Zoroastrianism was the religion of the rulers.
In his eastward sweep (334–330 BC ), Alexander the Great defeated vast Achaemenid forces and went on to capture Susa and to burn Persepolis. In the 3rd century BC , the Parthians moved into the area east of the Caspian and then into the Achaemenid Empire, establishing the new Parthian kingdom; later rulers moved west to come in contact with and then to fight the Roman Empire. The Parthians considered themselves spiritual heirs of the Achaemenids and adopted Zoroastrianism as the official religion. Weakened by long wars with Rome, the Parthians were followed by a local dynasty, the Sassanian, which arose in the area of Fars in southwestern Iran. Wars with Rome continued and were followed by a struggle with the Byzantine Empire. The Sassanian period ( AD 226–641) was one of cultural consolidation and was marked by economic prosperity and by a series of enlightened rulers.
During the first half of the 7th century AD , Arab warriors burst out of the Arabian Peninsula to overwhelm the Sassanian Empire and to spread the teachings of the prophet Muhammad, embodied in Islam. By the opening of the ninth century, Islamic doctrine and precepts had spread over the plateau, and local dynasties faithful to the Muslim creed emerged. Early in the 11th century, the Turkish Ghaznavid dynasty held power from western Iran to the Indus River. Their greatest ruler was Mahmud of Ghazni, a renowned conqueror and a patron of the arts. The Ghaznavids were replaced by the Seljuks, descended from Turkish nomad warriors enlisted in their service.
The Seljuk kingdom had its capital at Ray, just south of Tehran, and stretched from the Bosporus to Chinese Turkestan. Of rude origins, such rulers as Tughril Beg, Alp Arslan, and Malik Shah did much to promote cultural pursuits and enhance the character of Persian civilization.
In 1219, Mongol hordes under Genghis Khan (Temujin) began to move into Iran; successive waves subdued and devastated the country. Hulagu, a grandson of Genghis, settled in Maragheh in Azerbaijan and as Il-khan, or chief of the tribe, gave this title to the Il-khanid dynasty. His successors, such as Ghazan Khan and Oljaitu, ruled from Tabriz and Sultaniya, and once again untutored invaders became converts to Islam and patrons of Persian science, learning, and arts. Rivalries within the military leadership brought about the breakdown of Il-khanid power in the second half of the 14th century.
Qajar power began to fade at the turn of the 19th century. In the 1890s, Shi'a clerics led a national boycott that made the shah rescind a decree awarding a tobacco monopoly to a foreign agent. In 1906, a coalition of bazaar merchants, clerics, intellectuals, and tribal leaders forced the shah to accept a constitution. This liberal initiative was frustrated, however, by the power of the British and Russians, who controlled spheres of influence in the south and north of Iran. In 1380, Timur ("Timur the Lame," or, in the west Tamerlane) began to move into the Iranian plateau from the east. Within a decade, the entire area was in his power, bringing a renaissance of culture at Herat (in modern Afghanistan) and other towns, but later rulers lacked the force and ability to hold the empire together. Early in the 16th century a number of smaller, local dynasties emerged throughout Iran. The most powerful was the Safavid dynasty, whose leaders, descendants of a spiritual head of the Shi'a sect, imposed this form of Islam on their subjects. The fourth and greatest of this line, Shah Abbas (r.1587–1628), moved the capital to Esfahan, where he had many splendid buildings constructed. The Safavid period, marked by the emergence of a truly native Iranian dynasty after the lapse of many centuries, was a period of military power and general prosperity. However, decline set in, and in 1722, Esfahan fell to invading forces from Afghanistan. Nadir Shah, an Afshar tribesman from the north, drove off the Afghans and in 1736 established the Afshar dynasty. By the end of the 18th century, Zand rulers, dominant in the south, were replaced by the Qajars, a Turkish tribe.
After a period of chaos, the British arranged for a Persian Cossack officer, Reza Rhan, to come to power, first as minister of war in 1921, then prime minister, finally in 1925 as Reza Shah, the first sovereign of the Pahlavi dynasty. With ruthless authority, he sought to modernize Iran along the lines of Ataturk in Turkey. In 1941, suspecting him of pro-German sympathies, the British forced Reza Shah to abdicate in favor of his 21-year-old son, Muhammad Reza. British and Russian forces set up a supply line across Iran to the USSR. In April 1946, the British left, but the USSR refused to withdraw its forces. Under pressure from the UN and the United States, Soviet troops eventually withdrew in December 1946.
Oil, the source of nearly all Iran's national wealth, quickly came to dominate postwar politics. Muhammad Mossadeq, who as leader of the National Front in the national assembly (Majlis) led the fight in 1947 to deny the USSR oil concessions in northern Iran, became chairman of the oil committee of the Majlis. On 15 March 1951, the Majlis voted to nationalize the oil industry, which was dominated by the Anglo-Iranian Oil Co. (AIOC), a prewar concession to the United Kingdom. When the government of Prime Minister Hosein Ala took no immediate action against the AIOC, the Majlis demanded his resignation and the appointment of Mossadeq, who became prime minister in April. The AIOC was nationalized, but its output rapidly declined when the United Kingdom imposed an embargo on Iranian oil, as well as other economic sanctions. As Iran's economic situation worsened, Mossadeq sought to rally the people through fervent nationalistic appeals. An attempt by the shah to replace him failed in the summer of 1952, but by August 1953, Mossadeq had lost his parliamentary majority, but not his popular support. With the backing of a referendum, Mossadeq dissolved the Majlis and then refused to resign when the shah again tried to oust him. The shah fled Iran for four days but returned on 22 August, with backing from the military, the United States, and the United Kingdom. A new conservative government issued an appeal for aid; in September, the United States granted Iran $45 million. Mossadeq was convicted of treason in December.
After 1953, the shah began to consolidate his power. New arrangements between the National Iranian Oil Co. and a consortium of US, UK, and Dutch oil companies were negotiated during April–September 1954 and ratified by the Majlis in October. The left-wing Tudeh (Masses) Party, which had been banned in 1949 but had resurfaced during the Mossadeq regime, was suppressed after a Tudeh organization was exposed in the armed forces. In 1957, the government sponsored two new pseudo-parties, which contested parliamentary elections in 1960 and 1961. Meanwhile, Iran became affiliated with the Western alliance through the Baghdad Pact in 1955, later the Central Treaty Organization. (CENTO was dissolved after Iran pulled out in 1979.) Frontier demarcation agreements were signed with the USSR in April 1957.
US assistance and goodwill were plainly essential for the shah. In 1961, President John F. Kennedy urged him to undertake a more liberal program. Under the "white revolution" of 1962–63, the shah initiated land reform, electoral changes (including, for the first time, the right of women to hold and vote for public office), and broad economic development. Opposition to the reform program, the dictatorial regime, and the growing American influence was suppressed. Political dissent was not tolerated.
The shah's autocratic methods, his repressive use of the secret police (known as SAVAK), his program of rapid Westernization (at the expense of Islamic tradition), his emphasis on lavish display and costly arms imports, and his perceived tolerance of corruption and of US domination fed opposition in the late 1970s. The economic boom of the previous 15 years also came to an end. Islamic militants, radical students, and the middle class all joined in the revolt, until virtually the entire population turned against the shah. Following nine months of demonstrations and violent army reactions, martial law was declared in Iran's major cities in September 1978, but antigovernment strikes and massive marches could not be stopped. On 16 January 1979, the shah left Iran, appointing an old-line nationalist, Shahpur Bakhtiar, as prime minister. However, the leader of the Islamic opposition, Ayatollah Ruhollah Khomeini (the term ayatollah is the highest rank of the Shi'a clergy), who had spent 15 years in exile, first in Iraq and briefly in France, refused to deal with the Bakhtiar regime. Demonstrations continued, and on 1 February the ayatollah returned to a tumultuous welcome in Tehran. He quickly asserted control and appointed a provisional government, which took power after a military rebellion and the final collapse of the shah's regime on 11 February.
After a referendum, Khomeini on 1 April declared Iran an Islamic Republic. However, the provisional government, led by Medhi Bazargan and other liberal civilians, was unable to exercise control; revolutionary groups made indiscriminate arrests and summary executions of political opponents. Increasingly, radical clerics sought to take power for themselves. The crisis atmosphere was intensified by the seizure, on 4 November 1979, of 53 US hostages (50 of them in the US embassy compound in Tehran) by militant Iranian students who demanded the return of the shah from the United States (where he was receiving medical treatment) to stand trial in Iran. Despite vigorous protests by the US government, which froze Iranian assets in the United States, and by the UN over this violation of diplomatic immunity, the hostages were held for 444 days; in the intervening period, a US attempt to free the hostages by military force failed, and the shah died in Egypt on 27 July 1980. The crisis was finally resolved on 20 January 1981, in an agreement providing for release of the prisoners and the unfreezing of Iranian assets. A new constitution providing for an Islamic theocracy was ratified by popular referendum in December 1979. In presidential elections in January 1980, 'Abolhassan Bani-Sadr, a moderate who supported the revolution, was elected president. Later elections to the Majlis resulted in victory for the hard-line clerical Islamic Republican Party (IRP).
In June 1981, President Bani-Sadr was ousted by Khomeini; later that month, a bomb explosion at IRP headquarters in Tehran killed Ayatollah Beheshti, who had been serving as chief justice, as well as 4 cabinet ministers, 20 paramilitary deputies, and dozens of others. Another bombing, on 30 August, killed the new president, Muhammad 'Ali Rajai, and his new prime minister, Muhammad Javad Bahonar. The bombings were ascribed by the government to leftist guerrillas. By 1982, at least 4,500 people had been killed in political violence, and some estimates placed the total much higher. In September 1982, Sadegh Ghotbzadeh, who had been foreign minister during the hostage crisis, was executed on charges of plotting to kill Khomeini and establish a secular government.
Iraq, meanwhile, had taken advantage of Iran's political chaos and economic disorder to revive a border dispute that had been settled in 1975 when Iranian and Iraqi representatives reached agreement on the demarcation of their frontiers and Iran ended its support for rebellious Kurds, who were then defeated by the Iraqi army. Full-scale war erupted in September 1980, when Iraq demanded sovereignty over the entire Shatt al-'Arab waterway. Iraqi forces invaded Khuzistan in the southwest, and captured the town of Khorramshahr and the oil refinery center of Abadan. The Iranian army, decimated by the revolution, was slow to mobilize, but by June 1982 it had driven Iraqi soldiers out of Abadan and Khorramshahr and from all undisputed Iranian territory. Iran then launched its own offensive, invading Iraq and thrusting toward Basra, but failed to make significant gains. At this point the land war became stalemated, with Iranian and Iraqi troops setting up an elaborate system of trenches. In 1983, Iraq broadened the war zone to include oil-tanker traffic in the northern Persian Gulf.
The Iraqis first attacked Iranian oil installations, disrupting, but not stopping, oil exports from the main oil terminal at Kharg Island. In mid-1983, Iraq took delivery of French jets bearing Exocet missiles. Iran responded that it would close the Strait of Hormuz if Iraq used the missiles. The United States declared the strait a vital interest and said it would use military force to keep the strait open because of the large volume of oil that passed through it on the way to the West. During 1983, the Iraqis also began to attack civilian targets in Iran with long-range missiles. The attacks caused heavy casualties, and Iran responded by shelling Iraqi border cities. In 1984, Iran began to attack Arab shipping in the Persian Gulf.
Iranian forces staged a surprisingly effective attack on Iraqi forces in the Fao Peninsula in February 1986. The Iranians now controlled all of Iraq's border on the Persian Gulf and were in reach of the major Iraqi city of Basra. In April, Khomeini renewed his demands for an end to the war: Iraqi President Saddam Hussein must step down, and Iraq must admit responsibility and pay war reparations. Iran rejected all demands for a cease-fire and negotiations until its demands were met.
In November 1986, it was revealed that US National Security Adviser Robert McFarlane had secretly traveled to Iran to meet with government leaders. The United States supplied Iran with an estimated $30 million in spare parts and antiaircraft missiles in hopes that Iran would exert pressure on terrorist groups in Lebanon to release American hostages. In the wake of this affair, Iran in 1987 attacked Kuwaiti oil tankers reregistered as American tankers and laid mines in the Persian Gulf to disrupt oil tanker shipping. The United States responded by stationing a naval task force in the region and attacking Iranian patrol boats and oil-loading platforms and accidentally shot down a civilian passenger jet.
As the war continued to take a heavy toll in casualties and destruction and economic hardships persisted on the home front, the clerics maintained firm control through repression and Khomeini's charismatic hold over the people. In 1988, Iran finally yielded to terms for a cease-fire in the war. On 3 June 1989, a few months after calling for the death of novelist Salman Rushdie for blasphemy, Khomeini died of a heart attack. Over 3 million people attended his funeral. He was succeeded as the country's spiritual guide by President Ali Khamenei. On 28 July 1989, speaker of the parliament Ali Akbar Rafsanjani, a moderate, was elected president with 95% of the vote. Iran remained neutral during the Gulf War, receiving (and retaining) Iraqi planes that were flown across the border for safekeeping. Iran also accepted thousands of Kurdish refugees from Iraq to add to its heavy burden of Afghan refugees from the civil strife in that country. Inflation, shortages, and unemployment—the products of revolution, war, and mismanagement—continue to generate widespread popular discontent, fueled also by dissatisfaction with the closed and repressive political system.
President Rafsanjani was reelected by a significantly smaller margin in 1993 but continued to press for free-market economic reforms. Rising prices in the wake of decreased government economic subsidies led to civil unrest in 1994 and 1995. Clerical conservatives led by Khamenei continued to battle the political moderates for dominance in the 1996 parliamentary elections, without a decisive victory for either side. Then, in the presidential election of May 1997, a moderate cleric, Muhammed Khatami, who favored economic reform, a more conciliatory foreign-policy stance, and less rigid clerical control of the government, won over two-thirds of the vote. In spite of continued opposition by Islamic conservatives, Khatami established a more tolerant climate in the country and expanded civil liberties. His policies received a decisive endorsement by the Iranian electorate when a political coalition led by the reformist president won 141 out of 290 parliamentary seats in the February 2000 elections and 189 seats in the May runoff elections, despite the shutdown of over a dozen liberal newspapers by conservative elements in the government in the weeks preceding the May polling. On 8 June 2001, Khatami won a landslide reelection victory, securing nearly 80% of the popular vote.
United States president George W. Bush, in his 29 January 2002 State of the Union address, labeled Iran—along with Iraq and North Korea—an "axis of evil," responsible for seeking out weapons of mass destruction and supporting terrorists. Khatami, who has long advocated a more pro-Western stance, urged anti-US demonstrators to turn out in large numbers to protest the speech, as the speech had come as a surprise. Although Iran did not support the US-led military campaign in Afghanistan to oust the Taliban regime in late 2001, it had expressed sympathy for the 11 September 2001 attacks on the United States, and stated that it would aid any US service personnel in need on Iranian territory during the war in Afghanistan. Iran called the United States "ungrateful" for Iran's help in forming a post-Taliban government in Afghanistan, as Iran played a key role at the Bonn conference in December 2001 that established Afghanistan's transitional government. Iran supported a greater role for the UN in Afghanistan, and pledged resources to help train an Afghan army. Iran is concerned with securing its border with Afghanistan, to prevent further destabilization of the region.
In January 2003, Iran urged Iraq to cooperate with UN resolutions requiring it to disarm itself of weapons of mass destruction, in an effort to avoid war. Iran took the position that the United States must not take unilateral military action in the dispute, and said that it would not participate or allow its territory to be used in any military action against Iraq. Iran was again outraged by US president George W. Bush's 28 January 2003 State of the Union address, in which he alleged once again that Iran was developing weapons of mass destruction and supported terrorism.
In recent years, a youth movement has formed representing people who reject the theocracy of Iran's hard-line clerics and the "Islamic democracy" of the reformers. Many seek to live in a state based on the rule of law where the clergy's rule is abolished. In November 2002, Hashem Aghajari, a history professor, was sentenced to death on charges of insulting Islam. He had given a speech in which he stated that each generation should re-interpret aspects of Islam rather than simply following religious leaders. Thousands of students protested against the ruling—the largest in three years. Supreme Leader Ayatollah Khamenei ordered a review of the sentence two weeks after the student protests began. However, the head of the judiciary, Ayatollah Mahmoud Hashemi Shahroudi, stated that normal legal procedures would be followed to reconsider the verdict. Those procedures required an appeal, which Aghajari refused. His lawyer in December issued an appeal, and as of 31 January 2003, the case had not been resolved.