 Complete the following phrase:  Al-Mutasims reign was marked by continuous warfare. The two major internal campaigns of the reign were against the long-running Khurramite uprising of Babak Khorramdin in Adharbayjan, which was suppressed by al-Afshin in 835837, and against Mazyar, the autonomous ruler of Tabaristan, who had clashed with the Tahirid governor of Khorasan and risen up in revolt. While his generals led the fight against internal rebellions, al-Mutasim himself led the sole major external campaign of the period, in 838 against the Byzantine Empire. His armies defeated Emperor Theophilos and 