 As one of Harun 's younger sons , he was initially of little consequence . During the civil war between his elder half @-@ brothers al @-@ Amin ( r . 809 – 813 ) and al @-@ Ma 'mun ( r . 813 – 833 ) he remained in Baghdad , and , like most members of the Abbasid dynasty and the Abbasid aristocracy ( abnāʾ al @-@ dawla ) , supported the anti @-@ caliph Ibrahim ibn al @-@ Mahdi in 817 – 819 . Al @-@ Tabari records that Abu Ishaq led the pilgrimage in 816 , accompanied by many troops and officials , among whom was <unk> ibn Ali ibn Isa ibn <unk> , who had just been appointed to the governorship of the Yemen and was on his way there . During his stay in Mecca , his troops defeated and captured a pro @-@ Alid leader who had raided the pilgrim caravans . He also led the pilgrimage in the next year , but no details are known . 
