Dioceses of the Church of the East to 1318 to represent them. None of these four dioceses is mentioned again, and it is not clear when they lapsed. By the end of the 5th century there were at least three East Syriac dioceses in the Sassanian province of Media in western Iran. Canon XXI of the synod of Isaac in 410 foreshadowed the extension of the metropolitan principle to the bishops of Beth Madaye and other relatively remote regions. Hamadan (ancient Ecbatana) was the chief city of Media, and the Syriac name Beth Madaye (Media) was regularly used to refer to the East Syriac diocese of Hamadan as well
Ecbatana identifying the Ecbatana/Hagmatana mentioned in later Greek and Achaemenid sources with the city Sagbita/Sagbat frequently mentioned in Assyrian texts, since the Indo-Iranian sound /s/ became /h/ in many Iranian languages. The Sagbita mentioned by Assyrian sources was located in the proximity of the cities Kishesim (Kar-Nergal) and Harhar (Kar-Sharrukin). It is now proposed that the absence of any mention of Ecbatana in Assyrian sources can be explained by the possibility that Assyria never became involved as far east as the Alvand mountains, but only in the western Zagros. Sir Henry Rawlinson attempted to prove that there was a second and