Marwan II
Just as quickly as Qahtaba's forces marched from Khorosan to Kufa, so did the forces of Abdallah ibn Ali and Abu Awn Abd al-Malik ibn Yazid march on Mosul. At this point Marwan II mobilized his troops from Harran and advanced toward Mesopotamia. On 16 January 750 the two forces met on the left bank of a tributary of the Tigris in the Battle of the Zab, and nine days later Marwan II was defeated and his army was completely destroyed. The battle is regarded as what finally sealed the fate of the Umayyads. All Marwan II could do was flee through Syria and into Egypt, with each Umayyad town surrendering to the Abbasids as they swept through in pursuit.