Ali ibn Isa ibn Mahan

Ali ibn Isa ibn Mahan (died 3 July 811) was a prominent Abbasid military leader of the late 8th and early 9th centuries.

Ali's father, Isa ibn Mahan, was an early follower of the Abbasids, but mutinied after the Abbasid Revolution and was executed by Abu Muslim. Ali himself appears first in the reign of al-Mahdi (775–785) as commander of the caliphal guard (haras) and secretary of the army department (diwan al-jund). He continued in these offices under al-Hadi (r. 785–786), having in addition the powerful post of chamberlain (hajib). Under Harun al-Rashid (r. 786–809) he continued to serve as commander of the guard until 796, when he was named governor of Khurasan. As a leader of the abna′ al-dawla, the troops that formed the core of the Abbasid army in Iraq, he antagonized and Khurasanis and oppressed them through heavy taxation, with the revenue diverted for the upkeep of the abna′ and for filling his own coffers; during his eight-year tenure, he amassed a vast fortune. This resulted in the outbreak of a major rebellion under Rafi ibn al-Layth, which eventually required the personal intervention of Harun al-Rashid. Ali was imprisoned, but released on the death of Harun in March 809. He then sided, as many of the Baghdadi elites, with the new Caliph, al-Amin (r. 809–813), against his brother al-Ma'mun, who had been given a large viceregal domain encompassing Khurasan. The dissension between the two brothers and their supporters mounted until it finally spilled over into open warfare—the "Fourth Fitna"—in early 811. Ali was entrusted with a huge army of 40,000 men drawn from the abna′, but in the Battle of Rayy on 3 July 811 he was crushingly defeated and killed by a far smaller army under Tahir ibn al-Husayn.