Rise to power
On the death of Peroz I's father, Yazdegerd II, the younger son of the deceased emperor, Hormizd, seized the throne in the absence of his elder brother Peroz who had been posted as the governor of distant Sistan; Peroz was thus forced to seek the protection of the Hephthalites. The Hephthalite monarch, Khushnavaz, was glad to welcome him and aid him in his war against Hormizd. Peroz was also supported by Raham of the Mihran family. During this dynastic struggle, Denag, the mother of the two Sasanian princes, governed all of the Sasanian capital of Ctesiphon, or some parts of it.
With Hephthalite and Mihranid assistance, Peroz led an army against Hormizd, defeated him and held him captive. He then ceded Taliqan to Khushnavaz. Sources differ as to what happened to Hormizd after his capture. Some say that he was put to death. However, the Persian historian Mir-Khvand says that Peroz pardoned his younger brother and amicably spared his life.