Despite the presence of Caliph Marwan II with the main Umayyad army nearby in the Jazira, Abu Awn was not molested by the Umayyads,[8] and was able to join the new Abbasid general, Abdallah ibn Ali, in the decisive Battle of the Zab on 25 January 750, which resulted in the defeat and flight of Marwan II and the capitulation of the Umayyad heartland, Syria.[2]