The khawarij are members of a group that appeared in the first century of Islam during the First Fitna, the crisis of leadership after the death of Muhammed. It broke into revolt against the authority of the Rashidun Caliph Ali after he agreed to arbitration with his rival, Muawiyah, to decide the succession to the Caliphate following the Battle of Siffin. A Khariji later assassinated Ali and for hundreds of years, the Khawarij were a source of insurrection against the Caliphate.