Battle of Siffin

A prolonged battle in 657 CE near the Euphrates, in present-day Syria, between the forces of Ali ibn Abi Talib and those of Muawiya, governor of Syria, who refused to accept Ali's caliphate or hand over Uthman's killers for retribution. The fighting ended inconclusively after Muawiya's side proposed arbitration, which part of Ali's army pressured him to accept. The arbitration's outcome led directly to the Kharijites splitting off from Ali's camp.