Whakaotihia te rerenga e whai ake nei: I tenei mana, i te Hōngongoi-Akuhata 803, i arahi a Qasim i te whakaekenga ki Byzantine Asia Minor. I whakapaea e ia te pa kaha o Koron, i te wa i tukuna ai tana kaitohutohu a al-'Abbas ibn Ja'far ibn Muhammad ibn al-Ash'ath ki te whakapae i tetahi atu pa kaha, e mohiotia ana e nga Arapi ko Sinan. Heoi, i whakawhiwhia e nga Byzantines ki te tuku i nga herehere Muslim 320 mena ka wehe ia, a i whakaae ia. I te Hui-tanguru 808, i te wa i wehe atu ai a Harun i tana kaainga Raqqa mo tana haerenga tuarua ki Khurasan, i waiho e ia a Qasim hei kaiawhina ki Raqqa, me Khuzayma ibn Khazim hei kaitohutohu. Whai muri i te matenga o Harun me te urunga mai o al-Amin i te tau 809, i whakapumautia a Qasim i tona tuunga hei kawana mo te "al-'Awasim" me te "jund Qinnasrin", engari i te mea kua nekehia atu ia i tana kawana o te Jazira (Upper Mesopotamia), i reira i tohua ai a Khuzayma ibn Khazim. I te mutunga, i te tau 810, i nekehia a Qasim e Amin mai i ana kawanatanga katoa hei painga mo Khuzayma, a ka kawea mai ki te noho i raro i te tirotiro tata i Baghdad. I muri tata mai ka aukati a Amin i tana whakahua i roto i nga karakia, me Abdallah al-Ma'mun, i ara ake i te tutu tata i Khurasan. I te
I te pakanga ā-iwi i whai ake, i toa a Ma'mun, i patu, i whakamate i tana teina a Amin i te tau 813. I muri tonu mai, i whakakorehia a Qasim mai i tana tuunga hei kaiwhaiwhai.