Kammala wannan jumla: A shekara ta 810, Khalifa al-Amin, da dan uwansa, Al-Ma'mun, sun shiga rikici da juna, wanda daga baya ya haifar da yakin basasa; a watan Janairun 811, al-Amin ya fara fara mulkin
Babban yakin basasa na Abbasid lokacin da ya nada Ali ibn Isa a matsayin gwamnan Khurasan, ya sanya shi a kan babban rundunar sojoji 40,000, wanda aka samo daga wata kungiya mai suna "abna", kuma ya aike shi ya tsige al-Ma'mun. Lokacin da Ali ibn Isa ya tashi zuwa Khurasan, an ba da rahoton cewa ya ɗauki jerin sarƙoƙi na azurfa waɗanda za a ɗaure al-Ma'mun da su kuma a mayar da shi zuwa Baghdad. Labarin kusantar Ali ya jefa Khurasan cikin firgici, har ma al-Ma'mun ya yi tunanin guduwa. Sojojin da kawai yake da su shi ne karamin rundunar sojoji na kimanin mutane 4,000-5,000, a karkashin Tahir. An tura Tahir don fuskantar ci gaban Ali, amma an dauke shi a matsayin kusan aikin kashe kansa, har ma da mahaifin Tahir. Sojojin biyu sun hadu a Rayy, a kan iyakar yammacin Khurasan, kuma yakin da ya biyo baya (3 ga Yuli 811) ya haifar da babbar nasara ga Khurasanis, wanda aka kashe Ali kuma sojojinsa suka rushe a kan jirgin yamma.