Editing Al-Mu'tasim (section)

===Service under al-Ma'mun===
In 819 Abu Ishaq, accompanied by his Turkish guard and other commanders, was sent to suppress a [[Kharijite]] uprising under [[Mahdi ibn Alwan al-Haruri]] around [[Buzurj-Sabur]], north of Baghdad.{{sfn|Bosworth|1987|pp=67–68}} According to a most likely fanciful{{sfn|Bosworth|1991|p=98 (note 281)}} story provided by the 10th-century chronicler [[al-Tabari]], [[Ashinas]], in later years one of the chief Turkish leaders, received his name when he placed himself between a Kharijite lancer about to attack the future caliph, shouting, "Recognize me!" (in [[Persian language|Persian]] "''ashinas ma-ra''").{{sfn|Bosworth|1987|pp=67–68}}

In 828, al-Ma'mun appointed Abu Ishaq as governor of [[Egypt in the Middle Ages|Egypt]] and [[Bilad al-Sham|Syria]] in place of Abdallah ibn Tahir, who departed to assume the governorship of [[Khurasan]], while the [[Al-Jazira (caliphal province)|Jazira]] and the frontier zone (''[[thughur|thughūr]]'') with the Byzantine Empire passed to al-Abbas.{{sfn|Kennedy|2004a|p=157}}{{sfn|Bosworth|1987|p=178}} Ibn Tahir had just brought Egypt back under caliphal authority and pacified it after the tumult of the civil war,{{sfn|Kennedy|1998|pp=81–82|ignore-err=yes}} but the situation remained volatile. When Abu Ishaq's deputy in Egypt, [[Umayr ibn al-Walid]], tried to raise taxes, the [[Nile Delta]] and Hawf regions revolted. In 830, Umayr tried to forcibly subdue the rebels, but was ambushed and killed along with many of his troops. With the government troops confined to the capital, [[Fustat]], Abu Ishaq intervened in person, at the head of his 4,000 Turks. The rebels were soundly defeated and their leaders executed.{{sfn|Kennedy|1998|pp=82–83|ignore-err=yes}}{{sfn|Brett|2010|p=553}}

In July–September 830, al-Ma'mun, encouraged by perceived Byzantine weakness and suspicious of collusion between Emperor [[Theophilos (emperor)|Theophilos]] ({{reign|829|842}}) and the [[Khurramite]] rebels of [[Babak Khorramdin]], launched the first large-scale invasion of Byzantine territory since the start of the Abbasid civil war, and sacked several Byzantine border fortresses.{{sfn|El-Hibri|2010|p=290}}{{sfn|Treadgold|1988|pp=268, 272–273}} Following his return from Egypt, Abu Ishaq joined al-Ma'mun in his 831 campaign against the Byzantines. After rebuffing Theophilos' offers of peace, the Abbasid army passed through the [[Cilician Gates]] and divided into three columns, with the Caliph, his son al-Abbas, and Abu Ishaq at their head. The Abbasids seized and destroyed several minor forts as well as the town of [[Tyana]], while al-Abbas won a minor skirmish against a Byzantine army led by Theophilos in person, before withdrawing to Syria in September.{{sfn|Bosworth|1987|pp=186–188}}{{sfn|Treadgold|1988|pp=275–276}}

Soon after Abu Ishaq's departure from Egypt, the revolt flared up again, this time encompassing both the Arab settlers and the native Christian [[Copts]] under the leadership of Ibn Ubaydus, a descendant of one of the original [[Muslim conquest of Egypt|Arab conquerors]] of the country. The rebels were confronted by the Turks, led by al-Afshin. Al-Afshin conducted a systematic campaign, winning a string of victories and engaging in large-scale executions: many male Copts were executed and their women and children sold into slavery, while the old Arab elites who had ruled the country since the Muslim conquest of Egypt in the 640s were practically annihilated. In early 832, al-Ma'mun came to Egypt, and soon after the last elements of resistance, the Copts of the coastal marshes of the Nile Delta, were subdued.{{sfn|Brett|2010|p=553}}{{sfn|Kennedy|1998|p=83|ignore-err=yes}}

Later in the same year, al-Ma'mun repeated his invasion of the Byzantine borderlands, capturing the strategically important fortress of [[Loulon]], a success that consolidated Abbasid control of both exits of the Cilician Gates.{{sfn|Treadgold|1988|pp=278–279}} So encouraged was al-Ma'mun by this victory that he repeatedly rejected Theophilos' ever more generous offers for peace, and publicly announced that he intended to capture [[Constantinople]] itself. Consequently, al-Abbas was dispatched in May to convert the deserted town of Tyana into a military colony and prepare the ground for the westward advance. Al-Ma'mun followed in July, but he suddenly fell ill and died{{efn|The Arabic sources report anecdotal and widely diverging stories about al-Ma'mun's final illness, including a few that claim that he was poisoned by Abu Ishaq, or that his illness was the result of an "unnecessary surgery performed by a physician acting on [Abu Ishaq's] orders".{{sfn|Cooperson|2005|p=121}}}} on 7 August 833.{{sfn|Bosworth|1987|pp=198–199}}{{sfn|Treadgold|1988|pp=279–281}}