Empires of Iran

Founded by Cyrus II in 550 BCE and consolidated by Darius I, the Achaemenid Empire was the largest ancient state in history both by share of world population (~44%) and by territorial extent before the Mongols. It stretched from the Indus to the Aegean and from the Caucasus to Egypt's first cataract. Twenty satrapies, the Royal Road, the gold daric, the trilingual chancery (Old Persian, Elamite, Akkadian), the Behistun inscription, and the four ceremonial capitals — Pasargadae, Susa, Ecbatana, Persepolis — formed an administrative system whose imprint is still visible in the modern Iranian state.

The dynasty's tolerance of local cults and laws was famous in antiquity. The biblical books of Ezra and Nehemiah credit Cyrus and Darius with the rebuilding of the Jerusalem Temple; an Egyptian inscription of Darius's vizier Udjahorresnet praises him as restorer of the medical school of Saïs.

When Alexander died in Babylon in 323 BCE, his eastern domains passed to his general Seleucus I Nicator. The Seleucid Empire, capitaled at Seleucia-on-the-Tigris and later Antioch, was the greatest of the Hellenistic successor states. It founded dozens of Greek-style cities across Iran and Central Asia (including Ai Khanoum on the Oxus), introduced the Greek dating era — the first continuous numbered calendar in history — and minted the silver tetradrachm that became the standard coin from the Mediterranean to Bactria.

But the Seleucids never fully Hellenized the Iranian uplands. By 247 BCE the Parthians had broken away in the northeast, and by the mid-second century the Iranian heartland was lost.

The Arsacids ruled for nearly five centuries — longer than the Roman Empire ruled the western Mediterranean — and held Rome at the Euphrates. Their capital at Ctesiphon was sacked four times by Roman armies and rebuilt every time. At Carrhae (53 BCE), the cataphract-and-horse-archer combination annihilated Crassus's seven legions, and the "Parthian shot" entered the military vocabulary of every later empire.

Parthian rule was deliberately decentralized: a "king of kings" presided over a federation of vassal kingdoms (Elymais, Persis, Characene, Hatra, Armenia) that retained their own coinages and dynasties. This federalism, and the family quarrels it bred, would also be the dynasty's undoing.

The Sasanians revived the Achaemenid imperial idea with deliberate self-consciousness — even commissioning rock reliefs at Naqsh-e Rostam directly above the tombs of Darius and Xerxes. Shapur I defeated three Roman emperors (Gordian III, Philip the Arab, and Valerian, whom he captured alive). Khosrow I Anushirvan reformed taxation, codified law, founded the Academy of Gundishapur, and gave asylum to Greek philosophers expelled from Athens by Justinian.

"The Persians were the most refined of all peoples, and Khosrow Anushirvan the most just of all kings."

The empire's last decades were a perfect storm: a 26-year war of mutual exhaustion with Byzantium (602–628), the Justinianic plague's recurrent waves, and a succession crisis that put twelve rulers on the throne in four years. The Arab conquest in 636–651 ended the dynasty but transmitted Sasanian administrative practice — coin, tax, postal system, court ceremonial — directly to the Umayyad and Abbasid caliphates.

A Persian-Sunni dynasty of dehqān (landed nobility) origin, the Samanids ruled Khorasan and Transoxiana from Bukhara. Under their patronage New Persian — written in the Arabic script with a vastly enlarged Arabic vocabulary — replaced Pahlavi as the literary language of the Iranian world. The Samanid library at Bukhara was, in the words of the young Avicenna who used it, "such as I had never seen before nor since."

The court patronized Rudaki, the first major poet of New Persian; sponsored the historical works that would feed Ferdowsi's Shahnameh; and oversaw the early careers of al-Bīrūnī and Avicenna. The Samanid Mausoleum in Bukhara (c. 914) is the oldest surviving monument of Islamic Iranian architecture.

The Seljuks were Oghuz Turks from the steppes who in three generations conquered Iran, Iraq, the Caucasus, and most of Anatolia. Yet their administration, language of culture, and architectural taste were almost entirely Persian. The vizier Nizam al-Mulk's Siyāsatnāma ("Book of Government") remains a classic of Persian political theory; his network of Nizāmiyya madrasas standardized Sunni higher education across the Islamic world.

Under Seljuk patronage Omar Khayyam reformed the Persian calendar to an accuracy of one day in 5,000 years (the Gregorian managed one in 3,300 nearly 500 years later), and the four-iwan plan — which would dominate Iranian mosque, madrasa, and caravanserai design for the next 800 years — reached maturity in the Friday Mosque of Isfahan.

The Mongol invasions of 1219–1221 destroyed the cities of Khorasan, but the dynasty that emerged — the Ilkhanate, descended from Hulegu Khan, brother of Kublai — quickly converted to Islam, adopted Persian as the court language, and presided over one of the great ages of Iranian historiography, science, and the book arts. Rashid al-Din's Jāmi' al-Tawārīkh ("Compendium of Chronicles") is arguably the first world history. The Maragha observatory of Nasir al-Din al-Tusi (founded 1259) introduced the "Tusi couple" mathematical device that would later appear, unattributed, in Copernicus's De revolutionibus.

Shah Ismail I's establishment of Twelver Shi'ism as the state religion in 1501 reshaped the religious geography of the Middle East and gave modern Iran much of its distinctive character. Shah Abbas the Great (r. 1588–1629) moved the capital to Isfahan, built the Naqsh-e Jahan square — at over 89,000 m² one of the largest urban squares in the world — and welcomed Armenian merchants, Carmelite friars, and English East India Company envoys. The Sheikh Lotfollah Mosque on the eastern side of the square is, in the judgment of Robert Byron's Road to Oxiana, "one of the loveliest creations of human hand."

Nader Shah Afshar reunified Iran after the Safavid collapse and in 1739 sacked Mughal Delhi, returning with the Peacock Throne and the Koh-i-Noor diamond — booty so vast he suspended Iranian taxes for three years. His assassination in 1747 plunged the country into civil war, ended by the gentle rule of Karim Khan Zand from Shiraz (1751–1779), who modestly refused the title of shah and called himself only Vakil al-Ra'āyā, "Deputy of the People."

The Qajars presided over a long defensive contraction. Two Russo-Persian Wars cost Iran the entire Caucasus; the Anglo-Russian Convention of 1907 divided the country into spheres of influence; the D'Arcy concession of 1901 began the foreign exploitation of Iranian oil. Yet the same century also produced the first Iranian newspapers, the first telegraph and railway lines, the first modern university (the Dar al-Funun, 1851), and the Constitutional Revolution of 1905–1911 — the first popular constitutional movement in Asia.

Reza Shah built the Trans-Iranian Railway, secular law courts, the National Bank, and the University of Tehran. His son Mohammad Reza Shah oversaw the 1953 Anglo-American coup against Prime Minister Mosaddegh (who had nationalized the Anglo-Iranian Oil Company), the 1963 White Revolution land reforms, and the spectacular but unequal oil boom of the 1970s. The dynasty ended with the Islamic Revolution of 1979.

Approximate maximum territorial extent in thousands of square kilometers. Sources: Taagepera (1978, 1997), Cambridge History of Iran.