The Kharijites who had opposed 'Ali on the ground that he had no right to allow the appeal to arbitration, were defeated at Nahrawan or Nahrwan (658), but those who escaped became fierce propagandists against the Koreish, some claiming that the caliph should be chosen by the Faithful from any tribe of the Arabs, some that there should be no caliph at all, that God alone was their ruler and that the government should be carried on by a council.
He defeated the troops of Merwan I., but could not win the support of the Kharijites.
This has been essayed by Brunnow in his study on the Kharijites (aeiden, 1884), in which the narrative of Mubarrad in the Kamil is compared with the excerpts of Madaini given by Baladhuri and those of Abu Mikhnaf given by Tabari.
His son was besieged by Dahhak and his Kharijites and Saffarids in Nasibin; but a fierce battle at Mardin ended in Merwan's favour (745).
When the negotiations failed and war was resumed, the Kharijites refused to follow Ali's army, and he had to turn his armies in the first instance against them.