Rise to power
When Peroz's father Yazdegerd II died in 457, the elder brother and heir Hormizd ascended the throne at Ray. Peroz, with the support of the powerful Mihranid magnate Raham Mihran, fled to the northeastern part of the empire and began raising an army in order to claim the throne for himself. The empire thus fell into a dynastic struggle and became divided; the mother of the two brothers, Denag temporarily ruled as regent of the empire from its capital, Ctesiphon. According to eastern sources, Peroz was more worthy for the throne than Hormizd, who is called unfair. Only the anonymous source known as the Codex Sprenger 30 describes Hormizd as the "braver and better", whilst describing Peroz as "more learned in religion".
Peroz later went to the domains of the Hephthalite monarch Khushnavaz, who agreed to him support with soldiers in his struggle for the throne. In 459, Peroz, with Hephthalite and Mihranid assistance, led an army against Hormizd and defeated him. According to some sources, Hormizd was pardoned and spared by his brother. However, this is most likely a legend, which is disproved by other sources, that states Peroz had Hormizd and three members of his family killed. He then ceded Taliqan to Khushnavaz.