The regeneration of Old Iran, in opposition to the Arabs, found its firmest stronghold in Ghasna. The deeds of the Achæmenids were completely forgotten in the East which had no part in them; but the legends of Yima, Thraetaona, Kava Huçrava, and Kava Vistaçpa, had lived on under the dominion of the Achæmenids, the Seleucids, the Greek princes of Balkh and Cabul, and under the Arsacids. Then came the revival of the Avesta under Shapur II. about the middle of the fourth century A.D. (p. 61). The first Chosru (531-578 A.D.) caused the legends and traditions of the nation and the priests to be collected and copied; a comprehensive exposition of the whole was made under the last Yezdegerd. Thus as early as the last days of the Sassanids the tradition of Iran was collected and fixed, and this, transcribed in Pehlevi, outlived the fall of the kingdom, and descended as a legacy of ancient glory to the Soffarids, Samanids, and Ghasnavids.[437] On the basis of this "book of kings," which he possessed in an Arabic translation, Firdusi of Tus on the Tejend, a city of which at the present day some scanty ruins remain not far from Meshhed, undertook to restore to life the remembrance of the past of Eastern Iran and the fame of her ancient heroes in a great Epic poem. He gathered together the entire existing tradition, and under the dominion of Islam cast a new glory on the ancient belief in Auramazda, who was now known as Yazdan. This poem, the book of kings (Shahnameh) exhibits at the same time the New Persian language in its pure form, developed out of the Eastern dialects, and not yet contaminated with Aramæan and Arabic elements.