In Firdusi, Lohrasp, whom Chosru has made his successor, erects a fire-temple at Balkh, his royal abode, and after reigning 120 years, abdicates in favour of Gushtasp, his elder son, in order to devote his life to pious exercises at his temple. When Zartusht proclaims the Avesta, Gushtasp and his wife receive the new doctrine. But Arjasp, the king of Turan, sent Gushtasp a command not to listen to the words of Zartusht. To this request Gushtasp did not accede; a battle took place on the banks of the Oxus, which turned in favour of Iran, owing to the bravery of Zarir, the brother of Gushtasp. An arrow from an ambush lays the hero low at the moment of victory. His death terrifies the Iranians; not one of them ventures to avenge it till Gushtasp promises Isfendyar, the strongest and bravest of his sons, that he will give him the crown if he succeeds in avenging the death of Zarir. Isfendyar overthrows the warriors of Iran, brings the arms and horse of Zarir into the camp of Iran, and Arjasp retires into his land. In the place of the promised crown, Isfendyar receives from his father the high mission of spreading abroad the new faith. By means of a chain which he places on his neck, Zartusht makes Isfendyar invulnerable, and surrounds him with a charm so that anyone who slays him will himself quickly die. When Isfendyar returns home after a long time, his mission fully accomplished, as all have received the law of Zartusht, accusations are made against him that he is collecting an army to dethrone his father. On this unfounded charge Gushtasp causes Isfendyar to be cast into prison. But while he remains in Zabul, the Turanians attack Balkh. The aged Lohrasp takes up arms; he cannot check the Turanians; he falls; the city is taken: Zartusht with the fire-priests is slain in the fire-temple, the sacred fire is quenched in their blood, and two daughters of Gushtasp are carried away to Turan. In vain does Gushtasp hasten up, when he has collected his army; thirty-eight of his sons are slain in the battle against the Turanians. Gushtasp takes to flight, and with his warriors finds refuge in a mountain which is quickly invested by Arjasp. Then Jamasp, the faithful adviser of Gushtasp, passes in disguise through the camp of the Turanians, to fetch Isfendyar out of prison, and urge him to save his father and Iran. Forgetting his deep injury and wrong, Isfendyar forces a way through the camp of Arjasp, and in the subsequent battle slaughters so many of the enemy's men that he takes to flight. But the task is not yet accomplished; it still remains to set at liberty the two sisters whom the Turanians had carried away from Balkh, and whom Arjasp keeps imprisoned in "the brazen fortress." After seven conflicts, corresponding to those which Rustem had to undergo, when he liberated Kai Kaus from the power of the demons, Isfendyar reaches the fortress. He sends his army back, and in the guise of a merchant obtains entrance into the citadel.