General Notes

After about two decades of disturbed reigns (Ardashir II, Shapur III, Bahram IV), Yazdegerd I came to the throne. His reign is viewed differently by Christian and Zoroastrian sources. The former praise his clemency; the latter refer to him as "Yazdegerd the Sinful." His initial inclination toward tolerance of the Christian and Jewish religions was met by resistance on the part of the nobility. Because of their attitude
and because of the growing fanaticism of the Christians, Yazdegerd was forced to turn to repression.

After his death (420), the nobles refused to admit any of Yazdegerd's sons to the throne. But one of them, Bahram V, had the support of al-Mundhir, Arab prince of al-Hirah (east of the lower Euphrates) and a Sasanian vassal, and also, apparently, of Mihr-Narseh, chief minister of Yazdegerd's last years, who was retained in office, and Bahram eventually won the throne.
Source: www.eb.com