Farrokhzad, son of Hormozd, crossed the Arvand River in a fury of grief and launched a desperate assault at Karkh. Despite valiant resistance, as the dark dust of battle billowed across the plain, fortune turned against the Iranians, and their ranks broke before the Arab host. Farrokhzad returned to King Yazdegard III, caked in dust and crimson armor, his eyes weeping blood and his heart melting with sorrow. Prostrating before the monarch, he cried out: 'O last jewel of the Kayanid lineage! You stand alone while the enemy numbers a hundred thousand. Do not cast away the soul of Iran upon a desperate hazard. Fall back to the lush forests of Narvan, to Amol and Sari, where the people remain your devoted servants. There, like King Fereydun of old, gather a new host and reclaim your sovereignty!'
The following morning, Yazdegard ascended the throne in full majesty, wearing the Kayanid crown, and convened an assembly of wise mobads, grandees, and seasoned commanders. He presented Farrokhzad’s proposal, but the nobles resisted, declaring that flight to the woods ill-befitted a king. Yazdegard concurred, declaring that facing the enemy in battle was far nobler than bearing the shame of retreat. Yet, the King harbored another design: he would journey east to Khorasan. There, he intended to forge an alliance with the Khagan of China by taking the Faghfhur's daughter as his bride, and to call upon the formidable armies of the eastern marches. Furthermore, he counted on Mahoy, the Kanarang of Merv—a man of low birth whom Yazdegard had raised from a humble shepherd to a high commander.
Farrokhzad struck his hands together in dismay and passionately warned the King: 'Do not place your trust in the base-born! No spell or royal favor can alter an ignoble nature; he who was plucked from nothingness will turn his face when dark days fall.' But Yazdegard, swept by the relentless tide of fate, set his resolve. At dawn, the royal caravan struck out on the road to Khorasan.
A lamentation arose from the Iranian nobility, local landlords, and allies as they wept bitterly over the King's departure. Yazdegard, his eyelashes wet with tears, urged his loyal subjects to preserve their lives and estates, submitting to the changing sky until the storm of the Arab conquest might abate. Thus, with a sorrowful heart and a brow furrowed by anguish, the last Sasanian Emperor journeyed stage by stage through Ray and Gorgan toward Bost, unaware of the treacherous destiny awaiting him in the far reaches of Khorasan.