Mu'awiya (the Muslim Governor of Damascus) attempted to take the Caliphate from 'Ali (Muhammad's son-in-law and the 4th "orthodox" Caliph). This started the first civil war in Islam. 'Ali won the Battle of Siffin (657 A.D.) but eventually lost when he was compelled, by Mu'awiyah, to submit his claim to the Caliphate to arbitration.
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