in the border place of Muzn. In 826/7, Musa died and was succeeded by his son Muhammad ibn Musa, to whom Mazyar paid no attention. Mazyar continued to expand his influence, but his policies were regarded by the Muslims of Tabaristan as oppressive. The Muslims of Tabaristan and the Bavandid prince Qarin I now began complaining to al-Ma'mun about Mazyar's behavior, but did not manage to turn al-Ma'mun against Mazyar.

After al-Ma'mun became involved in a war against the Byzantine Empire, Mazyar used