Four substantial Syriac Orthodox dioceses are known to have existed before the fourteenth century in eastern Iran and Central Asia: Zarang (or Segestan), attested between the seventh and thirteenth centuries; Gurgan (later renamed Abaskun) to the south of the Caspian Sea between the eighth and tenth centuries; Aprah in Segestan between the eighth and eleventh centuries; and Herat, also between the eighth and eleventh centuries.
