The Sasanians

On the cliff at Naqsh-e Rostam, near Persepolis, below the tombs of the Achaemenid kings, a later king had himself carved on horseback. Before him a Roman emperor kneels, while another Roman stands with his wrist held fast. The rider is Shapur I, second king of the Sasanian dynasty, and the scene celebrates his victories over Rome, including the capture of the emperor Valerian in 260 CE. Valerian died in Persian captivity, the first Roman emperor taken prisoner by a foreign enemy. The dynasty took its name from Sasan, an ancestor of Ardashir I, who overthrew the Parthians in 224 CE. The Sasanians came from Fars, the old Persian heartland, and presented themselves as heirs of an Iranian past. Their kings called themselves 'king of kings of Iran', and the name Ērānšahr, 'realm of the Iranians', became the formal name of their state.

Fire and faith

Zoroastrianism, the faith taught by the prophet Zarathustra, received royal backing, and a powerful priesthood grew up around it. Fire temples, where a sacred flame was kept burning, were endowed across the empire. The population was never uniform in belief: Christians, Jews, Buddhists and Manichaeans lived within its borders, sometimes tolerated, sometimes persecuted. Mani, the founder of Manichaeism, was welcomed at Shapur's court but put to death under a later king in the 270s.

The best remembered Sasanian king is Khosrow I, called Anushirvan, 'of immortal soul', who reigned from 531 to 579. Persian and Arabic tradition made him the model of a just ruler. Tradition links his reign with the arrival from India of chess, chatrang in Middle Persian, and of a book of animal fables that the physician Borzuya translated from Sanskrit. In its later Arabic version it became Kalila wa Dimna, one of the most widely read books of the medieval world. At Ctesiphon the Sasanians built a palace whose brick arch, the Taq-e Kasra, still stands south of Baghdad, one of the largest unreinforced brick vaults ever built. At Taq-e Bostan, near Kermanshah, a grotto usually attributed to Khosrow II shows royal hunts in reed marshes, with boar driven by elephants and the king shooting from a boat.

The end came quickly. A long and exhausting war with Byzantium, from 602 to 628, left both empires drained. Within a decade Arab armies carrying the new faith of Islam advanced into Mesopotamia. The last king, Yazdegerd III, fled east and was killed near Merv in 651.