Marwan II
Marwan II dispatched the Qaysi Yazid ibn Umar to suppress the Alid-Yamani revolt in Kufa. Ultimately, the Yaman of Syria and Iraq, and the Kharijites under al-Dahhak al-Shaybani, were defeated by Marwan II's forces and a respite in the war was achieved by the spring of 748. However, by December 748, the Abbasid Revolution in Khurasan was in earnest and its leader, Abu Muslim, drove out the Qaysi governor Nasr ibn Sayyar from Merv and advanced westward. Yazid ibn Umar dispatched the Qaysi generals Nubata ibn Hanzala of Kilab and 'Amir ibn Dubara of Murrah to halt Abu Muslim's march, but they were defeated by Qahtaba ibn Shabib of Tayy. Iraq, with the exception of Qaysi-held Wasit, was conquered by the Abbasids under as-Saffah (r. 750–754) in October 749. Qaysi troops rallied behind Marwan II as he advanced against the Abbasids, but he was decisively defeated at the Battle of Zab in February 750; Umayyad power all but diminished as a result. When the Abbasid army reached Damascus in pursuit of Marwan II, Yamani tribesmen facilitated their entry into the city.