Following the killing of the governor Musa ibn Mus'ab al-Khath'ami in 785, Assamah took over his position and assumed command of the campaign to seize back control of the country from the rebel Dihyah ibn Mus'ab. Upon learning that Dihyah's lieutenant Yusuf ibn Nusayr al-Tujibi was preparing to assault the capital Fustat, the new governor sent his brother Bakkar to meet the insurgents in battle; the resulting encounter however proved to be a draw after Yusuf and Bakkar killed each other in single combat, causing their now leaderless armies to withdraw in confusion. A short time later, Assamah learned that he had been dismissed and replaced with al-Fadl ibn Salih, and his governorship was brought to an end after having lasted for around three months.[4]