The Fall of the Sasanian Empire — Rome’s last great rival conquered by the Arab armies

Summary

The Sasanian Empire — the last pre-Islamic Persian empire, founded by Ardashir I in 224 and ruled from its winter capital at Ctesiphon on the Tigris — was conquered by the Arab Muslim armies of the Rashidun Caliphate between roughly 633 and 651. Its last shah, Yazdegerd III, a grandson of the great king Khosrow II, fled eastward across his own collapsing realm for nearly a decade and was killed near Merv in 651, by tradition murdered by a local miller for the jewellery he carried. With his death the dynasty that had been Rome's and then Byzantium's principal rival for four centuries ceased to exist, and Iran began its long passage from Zoroastrian empire to part of the Islamic world.

The empire the Arabs broke was, like Byzantium that same century, already gravely wounded — and the wound was largely self-inflicted. The Sasanian and East Roman empires had fought a final, ruinous war from 602 to 628 in which Khosrow II overran Syria, Palestine, and Egypt before the emperor Heraclius drove deep into Persia and shattered his armies. Both empires emerged exhausted, bankrupt, and depopulated by war and plague. When Khosrow was murdered by his own nobles in 628, the Sasanian state fell into a four-year civil war in which a dozen or more claimants — including two queens, Boran and Azarmidokht — passed across the throne before the nobility agreed on the boy Yazdegerd III in 632.

It was onto this enfeebled, faction-ridden empire, not a Persia at its height, that the Arab armies advanced. The conquest came as a sequence of decisive battles against a state that could no longer absorb a single great defeat. At al-Qadisiyyah, around 636, the Arab commander Sa'd ibn Abi Waqqas destroyed the main Sasanian field army and killed its general Rostam Farrokhzad; Ctesiphon fell soon after; and at Nahavand in 642 — remembered in the Arab tradition as the "Victory of Victories" — the last great Persian army was annihilated. Thereafter the provinces fell one by one as Yazdegerd fled before them.

The consequences were civilizational. Zoroastrianism, the state religion, lost its imperial patronage and dwindled over centuries to a minority faith; Persian elites, language, and administrative genius were absorbed into the new caliphate, which they would in turn reshape; and the lands of Iran, conquered as Arab territory, became over generations a heartland of Islam while retaining a fiercely distinct Persian identity. Few conquests have so thoroughly ended one order and seeded another.

Timeline

An empire that ruled from the Euphrates to the Indus

For four centuries the Sasanian Empire was one of the two superpowers of late antiquity, the eastern counterweight to Rome. Founded in 224 when Ardashir I overthrew the last Parthian Arsacid king, it ruled an immense realm stretching at its height from Mesopotamia and the Caucasus across the Iranian plateau to the borders of India and Central Asia. Its kings styled themselves shahanshah, "king of kings," and presided over a sophisticated bureaucratic state, a class of great noble landholding families, and a powerful Zoroastrian priesthood whose fire-temples gave the empire its sacred ideology. Ctesiphon, on the Tigris near later Baghdad, was among the largest cities on earth.

This was the empire that had stood against Rome at the peak of Roman power and, more often than not, held its own. Sasanian armies had captured a Roman emperor, Valerian, in 260; their armored cataphract cavalry was the most feared in the world; and their wealth, drawn from the Mesopotamian floodplain and the Silk Road, was legendary. Persian art, administration, and learning radiated outward and would long outlast the dynasty itself. To its contemporaries the empire seemed as permanent a feature of the world as Rome.

Yet it carried structural strains that war would expose. Royal power depended on a fragile balance with the great aristocratic houses and the Zoroastrian clergy; a weak or contested king could see the nobility fracture into factions. The state was exposed along enormously long frontiers, and its prosperity depended on the irrigated heart of Mesopotamia, which a determined invader could reach and ruin. When the empire's leadership failed catastrophically in the early seventh century, these latent weaknesses became fatal.

Self-destruction, then the conquest

The catastrophe that opened the way to conquest was a war the Sasanians very nearly won. Beginning in 602, Khosrow II launched the last and greatest of the Roman–Persian wars, overrunning Syria, Palestine, and Egypt, carrying off the True Cross from Jerusalem, and pressing to the walls of Constantinople. But the Byzantine emperor Heraclius mounted a daring counteroffensive deep into the Persian heartland, destroyed Sasanian armies in the field, and sacked Khosrow's palace at Dastagerd. By 628 the war ended with both empires drained of men and money and ravaged by plague. The Sasanian state had spent its strength and gained nothing.

The political collapse followed at once. In 628 Khosrow II was deposed and executed by his own son and nobles, and the empire dissolved into a four-year civil war. Claimant after claimant — sons, generals, and the queens Boran and Azarmidokht — held the throne briefly before being killed or set aside, and the administration that bound the provinces to Ctesiphon broke down. When the nobility finally crowned the boy Yazdegerd III in 632, he inherited an exhausted treasury, a fractured aristocracy, and an army that had not recovered from Heraclius. At precisely this moment a new and unforeseen power emerged from Arabia.

The Arab conquest came as a sequence of battles that an intact empire might have survived but a broken one could not. Around 636, at al-Qadisiyyah near the Euphrates, the army under Sa'd ibn Abi Waqqas destroyed the main Sasanian force commanded by Rostam Farrokhzad, who was killed; the road to the capital lay open. Ctesiphon, abandoned by Yazdegerd and his court, fell in 637, and its vast treasury passed to the conquerors. The decisive blow came at Nahavand in 642, where the last great Persian army — by the chroniclers' accounts more than a hundred thousand strong — was lured from its fortified position and annihilated. After Nahavand, the chroniclers wrote, the Sasanians "never gathered an army again."

The Five Factors

Aftermath

The fall of the Sasanian Empire was one of the great hinges of world history. The lands of Iran, conquered as territory of the caliphate, were over the following centuries gradually and unevenly Islamized; Zoroastrianism, deprived of the patronage that had sustained it, declined from the religion of an empire to the faith of a persecuted minority, surviving among the Zoroastrians of Iran and the Parsis who later migrated to India. Yet Persian civilization was not erased. Its administrators staffed the caliphate, its literary and courtly traditions reshaped Islamic high culture, and a distinct Persian language and identity re-emerged with force in the centuries after the conquest.

The conquest also transformed the conquerors. The capture of the Sasanian treasury and the vast machinery of the Persian state gave the young caliphate wealth, models of governance, and a class of skilled officials it had not possessed. When the Abbasids built their capital at Baghdad in the eighth century — beside the ruins of Ctesiphon — they consciously inherited the Sasanian imperial style. Iran remembered Yazdegerd III as the tragic last king of an age the eleventh-century poet Ferdowsi would enshrine in the Shahnameh, the national epic, whose narrative closes with the fall of the dynasty and the coming of the Arabs.

Lessons

References

• Yazdegerd III | Sāsānian Dynasty, Last Ruler, Persian Empire ENCYCLOPÆDIA BRITANNICA
• Muslim conquest of Persia WIKIPEDIA
• Yazdegerd III WORLD HISTORY ENCYCLOPEDIA
• Battle of Nahāvand | Persian-Arab War, Umayyad Caliphate, Yazdegerd III ENCYCLOPÆDIA BRITANNICA
• Sasanian Empire WIKIPEDIA