(13th shahr of 25) The north. The Caspian distircts of Media formed a distinct geographical and ethnic region of Iran and tended toward political independence. Thus the "Letter of Tansar" represents King Gushnasp, at the beginning of the Sasanian period, as king of Gilan, Delam (Dailam) and Ruyan, Tabaristan, and Danbavand. This region formed the vassal kingdom, later province, of Parishkhwar (Parachoathras) Mountains, or in Book Pahlavi Padishkhwar (Fthasouar). Its major city, Rasht (Cyropolis), must have lain on the Parthian roads to the Araxes and into Atropatene. By this route Christianity could have reached the Gels as early as the 2nd century, although it became a diocese only in the sixth. To the south, via Shad Shapur (Qazvin), the Mah highway was accessible. Amul in Tabaristan connected with the highway, through Danbavand, and also communicated with Gurgan. The 20 foundations referred to in Shahristaniha i Eran might be fortifications built between the reigns of Yazdgard II and Khusrau I. A threat to Parishkhwar then existed from the Hun tribes of the Causcasus and especially from the Chol and Kidarites above Gurgan. The city Sariya on the Gurgan road was probably made such a defensive point.

Parishkhwar was notable for the persisting of the non-Iranian substrate within its population. These people were generally termed Aner, Strabo's Anariacae. In the west of the province, the Iranian Gels, who were noted warriors, dwelt int he coastal plain; their city varna lay near the corner of the Caspian. The Caspii themselves had been driven into the mountains. Next, to the east, lived the Cadusians, apparently mingled with the Gels; they dwelt from the coast into the mountains. The non-Iranian Amardi (Mardi) continued to inhabit the Amul region, although Phraates I had transported some to guard the Caspian Gates of Media. They were, however, mingled with the Tapurians, who had been transported there from Parthyene. Between the Amul (Amardus) river and the bay of Gurgan lived more non-Iranians, the Amariacae and Dribices. By Sasanian times these latter tribes were probably merging with Iranians into a common Mazan population. A gloss on Videvdad 1.17 would include the Delam in the substrate of western Parishkhwar.

-The Cambridge History of Iran, vol. 3(2): The Seleucid, Parthian, and Sasanian Periods, ed. Ehsan Yarshater (NY: Cambridge UP, 1983), 765-766.