Ardashir I, who deposed the last Parthian king at the battle of Hormozdgan in April 224 AD, was a deliberate restorationist. He came from Persis — the original Achaemenid heartland — and he traced his dynasty's legitimacy back, by a route that was probably more political than genealogical, to the family of Cyrus. He took the old Achaemenid royal title (shahanshah, king of kings, "of Iran and non-Iran") and he made the Zoroastrian priesthood, which had survived the Hellenistic and Parthian centuries in something like an unofficial state of opposition, the official cult of the new empire. The Sasanian Empire that he founded would last for 427 years, longer than any other state in Iranian history, and would be the second of the two great empires of late antiquity, the rival and counterpart of Rome and Byzantium.
The Sasanian state at its height ran from the Euphrates frontier with Rome to the Oxus, and from the Caucasus to the Persian Gulf. It included most of modern Iran, Iraq, eastern Turkey, Armenia, Azerbaijan, parts of Afghanistan and Central Asia, and, intermittently, eastern Arabia and Yemen. Its capital was Ctesiphon, the old Parthian capital, which the Sasanians enlarged and embellished with monumental architecture, including the great barrel-vaulted audience hall of Khosrow I — the Taq-e Kasra — that still stands in ruined form south of Baghdad. Its population at peak is estimated at twenty to thirty million people. Its army was based on the same heavy cavalry that had won at Carrhae, supplemented by Indian war elephants and a corps of Daylamite infantry from the Caspian mountains.
Zoroastrianism as state religion
Zoroastrianism — the dualist monotheism founded, at an uncertain date probably between 1500 and 1000 BC, by the Iranian prophet Zarathustra (Greek Zoroaster) — had been the religion of the Achaemenid kings, but had not been imposed on their subjects. Under the Sasanians, for the first time, it became the official state religion of an Iranian empire. The high priest of the empire (the mowbedan mowbed) was the second figure in the state after the king. Fire temples were built throughout the empire; the major surviving ones (Adur Gushnasp at Takht-e Soleyman in north-western Iran, Adur Farnbag in Fars) are extraordinary buildings, with the sacred fires kept burning by hereditary priesthoods for centuries. The Avesta, the Zoroastrian scriptures, was written down for the first time in this period in a specially invented alphabet, the Avestan script, which had fifty-three letters in order to record the precise phonetics of liturgical recitation.
The dark side of state Zoroastrianism was active persecution. Christians, Manichaeans, Mazdakites, Jews, and Buddhists were all, at various times, persecuted by the Sasanian state, sometimes severely. The Manichaean prophet Mani, who had been welcomed at court by Shapur I in the 240s and had attempted to synthesise Zoroastrianism, Christianity, and Buddhism into a new universal religion, was arrested and executed by Bahram I in 276 or 277 AD. The Mazdakite movement — a radical egalitarian Zoroastrian sect that demanded the redistribution of property and (according to its enemies) of women — was crushed by Khosrow I in 528 AD with mass executions, after a generation of toleration under his father Kavadh I. The Sasanian model of unified state-and-church would be inherited, with all of its strengths and its repressive tendencies, by the early Islamic caliphates.
The duel with Rome
The Sasanian–Roman wars lasted, with intervals of peace, from 230 to 628 AD. The frontier ran along the upper Euphrates and through Armenia, and was disputed for four centuries. The principal episodes were the capture of three Roman emperors by the Sasanians — Valerian, taken alive by Shapur I at the battle of Edessa in 260 AD, was famously made to serve as a footstool for the Sasanian king when he mounted his horse — and the four-times sack of Ctesiphon by the Romans (Trajan 116, Lucius Verus 165, Septimius Severus 198, Carus 283), each followed by Roman withdrawal. The wars were a luxury that neither empire could afford. They drained both armies, both treasuries, and the agricultural base of the Mesopotamian plain, which was repeatedly devastated.
The final round, under Khosrow II (590-628), was an astonishing series of Sasanian victories: Antioch fell in 611, Damascus in 613, Jerusalem in 614 (the True Cross was carried off as plunder to Ctesiphon), Alexandria and the entire Egyptian provincial granary in 619. The Byzantine empire, on the brink of collapse, was rescued by the emperor Heraclius, who in 622 launched a counter-invasion deep into Iran. By 628 his army was forty kilometres from Ctesiphon. Khosrow II was deposed and murdered by his own son. Heraclius dictated peace on Roman terms. The True Cross was returned to Jerusalem with great ceremony in 630. Both empires were exhausted. Four years later, the first armies of a new power emerged from the Arabian peninsula. Neither empire was in any condition to resist.
Khosrow I and the silver age
The Sasanians are remembered, in Iranian cultural memory, principally for their high culture rather than their wars. Under Khosrow I Anushirvan (the Immortal Soul, r. 531–579 AD), the empire reached the peak of its administrative and intellectual prestige. Khosrow reformed the tax system to a fixed land tax in cash, which Islamic states would inherit and continue for a thousand years. He founded the Academy of Gondishapur in southwestern Iran, where Greek philosophical and medical texts were translated into Pahlavi (Middle Persian) and Syriac, and where physicians from across the late-antique world taught and practised. (When the emperor Justinian closed the Athenian Academy of Plato in 529 AD, several of its philosophers emigrated to Khosrow's court.) Khosrow's chancellor Bozorgmehr is the protagonist of a cycle of moral and political anecdotes that Iranian schoolchildren still memorise. Chess arrived from India during his reign and acquired its Persian vocabulary (shah, shah mat — the king is helpless).
The Sasanian silver-plate court art — large drinking vessels and dishes embossed with hunting scenes of the king of kings — is preserved in collections from the Hermitage to the Metropolitan Museum. The textile patterns developed at the Sasanian court — the so-called Senmurv, the winged composite creature; the pearl-roundel motif; the symmetrical hunters — were exported along the Silk Road and survived the empire by centuries. They reappear in early Tang Chinese porcelain, in seventh-century Byzantine silks, and in the textile patterns of Carolingian Aachen.
The Arab conquest
The Sasanian state was destroyed by the armies of the Rashidun Caliphate in fifteen years (633–651). The decisive battle was at al-Qadisiyyah, near Najaf in southern Iraq, in November 636. A Sasanian army of about 60,000 troops under the general Rostam Farrokhzad was defeated over four days by a smaller Arab force under Sa'd ibn Abi Waqqas. Rostam was killed. Ctesiphon fell in March 637 and was looted on a scale that the Arab chroniclers themselves found uncomfortable to record. The last Sasanian king, the boy emperor Yazdegerd III, fled east, hoping to raise new armies in the Iranian provinces. He was murdered in 651 at Merv (modern Turkmenistan) by a local miller who wanted his clothes. He was the last king of pre-Islamic Iran. The dynasty he came from had ruled for four centuries. The civilisation it had been the political head of would survive, in transformed condition, into the Islamic period — the subject of the next chapter.
"I left a city that I had made the wealthiest in the world. I leave a desert." — Yazdegerd III, on the burning of Ctesiphon (apocryphal, but Iranian tradition)
End of Chapter III