Al-Abbas ibn al-Ma'mun

Al-Abbas ibn al-Ma'mun (died 838 CE) was an Arab prince and general, the son of the Abbasid Caliph al-Ma'mun (r. 813–833 CE). A distinguished military leader in the Byzantine–Arab Wars, he was passed over in the succession in favour of his uncle al-Mu'tasim (r. 833–842 CE). In 838, he was arrested for his involvement in a failed conspiracy against Mu'tasim, and died in prison.

Abbas was the only son of Ma'mun, who in 828–829 appointed him as governor of Al-Jazira (Upper Mesopotamia) and the Mesopotamian military frontier zone (thughur) with the Byzantine Empire. Abbas distinguished himself in the expeditions against Byzantium for his bravery. In the summer of 830, Abbas led an expedition against the Khurramite rebels of Babak Khorramdin in Azerbaijan. The campaign was accompanied by a contingent of Byzantine captives under the renegade general Manuel the Armenian, who, given Abbas's relative inexperience, may have been the actual commander of the army. Abbas's force met with some success against the Khurramites, and began its return. As it passed near the Byzantine frontier at Adata, Manuel, having earned the confidence of Abbas and his Arab officers, persuaded Abbas to cross the nearby passes and raid Byzantine territory. Once there, Manuel took advantage of a hunt to disarm Abbas and his entourage and defect back to the Empire, along with some of the other Byzantine captives. Abbas with his men were left behind and after rejoining their army, they retreated back over the mountains into the Caliphate.

In the next year, however, Abbas accompanied his father and uncle in a major expedition into Byzantine Anatolia. After the Arab army crossed the Cilician Gates and took Heraclea Cybistra in early July, it divided in three corps, headed by the Caliph, Mu'tasim and Abbas, and proceeded to raid across Cappadocia. The other two forces achieved little of consequence in the already repeatedly devastated area, but Abbas met with more success: he forced the town of Tyana to capitulate and razed it, and met and defeated the Byzantine army under the emperor Theophilos (r. 829–842) in a minor skirmish. Ma'mun kept up the pressure on Byzantium in 832, with his army capturing the strategically important fortress of Loulon, and in late 832 the Caliph began gathering a huge army and announced that he intended to conquer and colonize Anatolia step by step, and finally subjugate the Empire by capturing Constantinople itself. Consequently, on 25 May 833, Abbas with the advance force marched into Byzantine territory and began creating a military base at the site of Tyana. The site had been fortified and awaited the arrival of the Caliph's army, which in early July crossed into Anatolia. At this juncture, fortunately for the Byzantines, Ma'mun fell ill and died, although some modern scholars speculate that his death may have been the result of a coup.

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