The principal cause of the rebellion was the increasing gap between the outlying peoples of the Caliphate and the Damascus-based Umayyad government.

Marwan's army was, on paper at least, far larger and more formidable than that of his opponents, as it contained many veterans of earlier Umayyad campaigns against the Byzantine Empire; its support for the caliph, however, was only lukewarm.

The Abbasid army formed a spear wall, a tactic they had adopted from their Umayyad opponents, presumably from witnessing it in earlier battles.

This entailed standing in a battle line with their lances pointed at the enemy (similar to the stakes used by English longbowmen at Agincourt and Crécy many centuries later).

Marwan II himself escaped the battlefield and fled down the Levant, pursued relentlessly by the Abbasids, who met no serious resistance from the Syrians because the land had recently been laid waste by an earthquake and pestilence.