During the reign of al-Mahdi (r. 775–785) Isa ibn Musa was permanently stripped of his succession rights to the caliphate,[6] but aside from this Musa and his family appear to have remained in good standing. In 780 he escorted the future caliph Harun al-Rashid on an expedition against the Byzantine Empire,[7] and following the death of Isa in 783 he was given the governorship of his father's old power base of Kufa.[8]