Persian Civil War of 718

Between 718 and 736 a brutal civil war was fought in Iran between rival branches of the Sassanid Dynasty, their supporters and external allies. The cause of the dispute was a succession crisis which had taken place almost a hundred years earlier, when the child emperor Yazdegerd III was overthrown by his cousin, the usurper Shahryar I, and his family were forced to flee into exile.

Despite repeated assassination attempts by Shahryar's agents, Yazdegerd and his family found shelter in India. His son and grandson established a powerful state there, the Third Indo-Sassanid Empire, but continued to harbour ambitions to retake Iran. In 718 therefore Yazdegerd's grandson Narsieh, allying with disaffected elements among the Persian nobility and with the tacit support of Rome, launched an invasion into the eastern Iranian Plateau.