High Quality Content by WIKIPEDIA articles! Yazdegerd I, or Izdekerti ("made by God", modern Persian: ; in Greek accounts , Isdigerd s), was the thirteenth Sassanid king of Persia and ruled from 399 to 421. HE is believed by some to be the son of Shapur III (383 388) and by others to be son of Bahram IV (388 389). HE succeeded to the Persian throne on the assassination of Bahram IV in 399 and ruled for twenty-one years till his death in 421. YAzdegerd I's reign is largely uneventful. THe king is described as being of a peaceful disposition. THere were cordial relations between Persia and the Eastern Roman Empire as well as between Persia and the Western Roman Empire. EArly during his reign, Yazdegerd was entrusted the care of the Roman prince Theodosius by his father Arcadius on the latter's death in 408, and Yazdegerd faithfully defended the life, power and possessions of the Roman prince.