Middle Ages (652–1501)

Between 633 and 642, Caliphs of the newly founded Islamic Empire invaded the Sassanid Empire. By 642 Umar, after a series of victories over the Sassanid Empire conquered the whole of the Persian empire. After the Islamic conquest of Persia, Iran was annexed into the Arab Umayyad Caliphate. But the Islamization of Iran was to yield deep transformations within the cultural, scientific, and political structure of Iran's society: The blossoming of Persian literature, philosophy, medicine and art became major elements of the newly-forming Muslim civilization, culturally, politically, and religiously. The Iranian contribution to this new Islamic civilization caused the Islamic Golden Age.

Abu Moslem, an Iranian general, expelled the Umayyads from Damascus and helped the Abbasid caliphs to conquer Baghdad. The Abbasid caliphs frequently chose their "wazirs" (viziers) among Iranians, and Iranian governors acquired a certain amount of local autonomy. Thus in 822, the governor of Khorasan, Tahir, proclaimed his independence and founded a new Persian dynasty of Tahirids. And by the Samanid era, Iran's efforts to regain its independence had been well solidified.

Attempts of Arabization thus never succeeded in Iran, and movements such as the Shuubiyah became catalysts for Iranians to regain their independence in their relations with the Arab invaders. The cultural revival of the post-Abbasid period led to a resurfacing of Iranian national identity. The resulting cultural movement reached its peak during the 9th and 10th centuries. The most notable effect of the movement was the continuation of the Persian language, the language of the Persians and the official language of Iran to the present day. Ferdowsi, Iran's greatest epic poet, is regarded today as the most important figure in maintaining the Persian language. After an interval of silence Iran re-emerged as a separate, different and distinctive element within Islam. Iranian philosophy after the Islamic conquest, is characterized by different interactions with the Old Iranian philosophy, the Greek philosophy and with the development of Islamic philosophy. The Illumination School and the Transcendent Philosophy are regarded as two of the main philosophical traditions of that era in Persia. The movement continued well into the 11th century, when Mahmud-a Ghaznavi founded a vast empire, with its capital at Isfahan and Ghazna. Their successors, the Seljuks, asserted their domination from the Mediterranean Sea to Central Asia. As with their predecessors, the divan of the empire was in the hands of Iranian viziers, who founded the Nizamiyya.

During this period, hundreds of scholars and scientists vastly contributed to technology, science and medicine, later influencing the rise of European science during the Renaissance.

In 1218, the eastern Khwarazmid provinces of Transoxiana and Khorasan suffered a devastating invasion by Genghis Khan. During this period more than half of Iran's population was killed, turning the streets of Persian cities like Neishabur into "rivers of blood", as the severed heads of men, women, and children were "neatly stacked into carefully constructed pyramids around which the carcasses of the city's dogs and cats were placed". Between 1220 and 1260, the total population of Iran had dropped from 2,500,000 to 250,000 as a result of mass extermination and famine.

In a letter to King Louis IX of France, Holaku, one of the Genghis Khan's grandsons, alone took responsibility for 200,000 deaths in his raids of Iran and the Caliphate. He was followed by yet another conqueror, Tamerlane, who established his capital in Samarkand. The waves of devastation prevented many cities such as Neishabur from reaching their pre-invasion population levels until the 20th century, eight centuries later.

But both Hulagu, Timur, and their successors soon came to adopt the ways and customs of that which they had conquered, choosing to surround themselves with a culture that was distinctively Persian.

Early Modern Era (1501–1921)

Iran's first encompassing Shi'a Islamic state was established under theSafavid Dynasty in 1501 by Shah Ismail I. The Safavid Dynasty soon became a major political power and promoted the flow of bilateral state contacts. The Safavid peak was during the rule of Shah Abbas The Great The Safavid Dynasty frequently locked horns with the Ottoman Empire, Uzbek tribes and the Portuguese Empire. The Safavids moved their capital from Tabriz to Qazvin and then to Isfahan where their patronage for the arts propelled Iran into one of its most aesthetically productive eras. Under their rule, the state became highly centralized, the first attempts to modernize the military were made, and even a distinct style of architecture developed. In 1722 Afghan rebels defeated Shah Sultan Hossein and ended the Safavid Dynasty, but in 1735, Nader Shah successfully drove out the Afghan rebels from Isfahan and established the Afsharid Dynasty. He then staged an incursion into India in 1738 securing the Peacock throne, Koh-i-Noor, and Darya-ye Noor among other royal treasures. His rule did not last long however, and he was assassinated in 1747. The Mashhad based Afshar Dynasty was succeeded by the Zand dynasty in 1750, founded by Karim Khan, who established his capital at Shiraz. His rule brought a period of relative peace and renewed prosperity.

The Zand dynasty lasted three generations, until Aga Muhammad Khan executed Lotf Ali Khan, and founded his new capital in Tehran, marking the dawn of the Qajar Dynasty in 1794. The capable Qajar chancellor Amir Kabir established Iran's first modern college system, among other modernizing reforms. Iran suffered several wars with Imperial Russia during the Qajar era, resulting in Iran losing almost half of its territories to Imperial Russia and the British Empire, via the treaties of Gulistan, Turkmenchay and Akhal. In spite of The Great Game Iran managed to maintain her sovereignty and was never colonized, unlike neighbouring states in the region. Repeated foreign intervention and a corrupt and weakened Qajar rule led to various protests, which by the end of the Qajar period resulted in Persia's constitutional revolution establishing the nation's first parliament in 1906, within a constitutional monarchy.

Recent history (1921–)

In 1925, Reza Khan overthrew the weakening Qajar Dynasty and became Shah. Reza Shah initiated industrialization, railroad construction, and the establishment of a national education system. Reza Shah sought to balance Russian and British influence, but when World War II started, his nascent ties to Germany alarmed Britain and Russia. In 1941, Britain and the USSR invaded Iran in order to utilize Iranian railroad capacity during World War II. The Shah was forced to abdicate in favour of his son, Mohammad Reza Pahlavi.

In 1951 Dr. Mohammed Mossadegh was elected prime minister. As prime minister, Mossadegh became enormously popular in Iran after he nationalized Iran's oil reserves. In response, Britain embargoed Iranian oil and, amidst Cold War fears, invited the United States to join in a plot to depose Mossadegh, and in 1953 President Dwight D. Eisenhower authorized Operation Ajax. The operation was successful, and Mossadegh was arrested on 19 August 1953. After Operation Ajax, Mohammad Reza Pahlavi's rule became increasingly autocratic. With American support, the Shah was able to rapidly modernize Iranian infrastructure, but he simultaneously crushed all forms of political opposition with his intelligence agency, SAVAK. Ayatollah Ruhollah Khomeini became an active critic of the Shah's White Revolution and publicly denounced the government. Khomeini was arrested and imprisoned for 18 months. After his release in 1964 Khomeini publicly criticized the United States government. The Shah was persuaded to send him into exile by General Hassan Pakravan. Khomeini was sent first to Turkey, then to Iraq and finally to France. While in exile he continued to denounce the Shah.

The Iranian Revolution, also known as the Islamic Revolution, began in January 1978 with the first major demonstrations against the Shah. After strikes and demonstrations paralysed the country and its economy, the Shah fled the country in January 1979 and Ayatollah Khomeini soon returned from exile to Tehran. The Pahlavi Dynasty collapsed ten days later on 11 February when Iran's military declared itself "neutral" after guerrillas and rebel troops overwhelmed troops loyal to the Shah in armed street fighting. Iran officially became an Islamic Republic on 1 April 1979 when Iranians overwhelmingly approved a national referendum to make it so. In December 1979 the country approved a theocratic constitution, whereby Khomeini became Supreme Leader of the country.

The speed and success of the revolution surprised many throughout the world, as it had not been precipitated by a military defeat, a financial crisis, or a peasant rebellion. Although both nationalists and Marxists joined with Islamic traditionalists to overthrow the Shah, tens of thousands were killed and executed by the Islamic regime afterward, the revolution ultimately resulted in an Islamic Republic under Ayatollah Ruhollah Khomeini.

After a group of Iranian students seized US embassy personnel on 4 November 1979, In which 66 US embassy personnel were seized its relationship with the United States deteriorated rapidly. The students labelled the embassy a "den of spies" and the personnel were accused of plotting to overthrow the new government, as the CIA had done to Mohammad Mossadegh in 1953. While the student ringleaders had not asked for permission from Khomeini to seize the embassy, Khomeini nonetheless supported the embassy takeover after hearing of its success. While most of the female and African American hostages were released within the first months, the remaining fifty-two hostages were held for 444 days. Subsequently attempts by the Jimmy Carter administration to negotiate or rescue were unsuccessful. In January 1981 the hostages were set free according to the Algiers declaration.

Iraqi leader Saddam Hussein decided to take advantage of what he perceived to be disorder in the wake of the Iranian Revolution and its unpopularity with Western governments. The once-strong Iranian military had been disbanded during the revolution. Saddam sought to expand Iraq's access to the Persian Gulf by acquiring territories that Iraq had claimed earlier from Iran during the Shah's rule. Of chief importance to Iraq was Khuzestan which not only has a substantial Arab population, but boasted rich oil fields as well. On the unilateral behalf of the United Arab Emirates, the islands of Abu Musa and the Greater and Lesser Tunbs became objectives as well. On 22 September 1980 the Iraqi army invaded Iran at Khuzestan, precipitating the Iran–Iraq War.

Although Saddam Hussein's forces made several early advances, by 1982, Iranian forces managed to push the Iraqi army back into Iraq. Khomeini sought to export his Islamic revolution westward into Iraq, especially on the majority Shi'a Arabs living in the country. The war then continued for six more years until 1988, when Khomeini, in his words, "drank the cup of poison" and accepted a truce mediated by the United Nations. The total Iranian casualties of the war were estimated to be anywhere between 500,000 and 1,000,000; with more than 100,000 Iranian being victims of Iraq's chemical weapons Almost all relevant international agencies have confirmed that Saddam engaged in chemical warfare to blunt Iranian human wave attacks; these agencies unanimously confirmed that Iran never used chemical weapons during the war.

Following the Iran–Iraq War President Akbar Hashemi Rafsanjani and his administration concentrated on a pragmatic pro-business policy of rebuilding and strengthening the economy without making any dramatic break with the ideology of the revolution. Rafsanjani served until 1997 when he was succeeded by the moderate reformist Mohammad Khatami. During his two terms as president, Khatami advocated freedom of expression, tolerance and civil society, constructive diplomatic relations with other states including EU and Asian governments, and an economic policy that supported free market and foreign investment. However, Khatami is widely regarded as having been unsuccessful in achieving his goal of making Iran more free and democratic. In the 2005 presidential elections Iran made yet another change in political direction when conservative populist candidate Mahmoud Ahmadinejad, was elected over Akbar Hashemi Rafsanjani.