Al-Tabari recorded that Babak started his revolt in 816–817. At first, Caliph al-Ma′mun paid little attention to the′s uprising because of the difficulty in intervening from far-away Khorasan, the appointment of his successor and the actions of al-Fadl ibn Sahl. Those circumstances paved the way for Babak and his supporters. The caliph sent General Yahya ibn Mu'adh to fight Babak in 819–820, but Babak was undefeated several times. Two years later, Babak overcome the forces of Isa ibn Muhammad ibn Abi Khalid.