Yazdegerd III, ("made by God," Izdegerdes), king of Persia, a grandson of Khosrau II, who had been murdered by his son Kavadh II in 628, was raised to the throne in 632 after a series of internal conflicts.
He was a mere child and never really ruled; in his first year the Arabic invasion began, and in 637 the battle of Kadisiya decided the fate of the empire.
Ctesiphon was occupied by the Arabs, and the king fled into Media. Yazdegerd fled from one district to another, till at last he was murdered at Merv in 651. The Parsees, who use the old Persian calendar, continue to count the years from his accession (era of Yazdegerd, beginning June 16, AD 632).
His daughter Shahr Banu would be married to the grandson of Muhammad, Husayn ibn Ali, and gave birth to the fourth Shia Imam, Ali Zayn al Abidin.