First Fitna: Battle of Siffin

July 26, 657 - The forces Ali ibn Abi Talib clash with those of Muawiyah I on the Plain of Siffin in Syria. Fought in an attempt to reunite the Muslim Empire after the death of Caliph Uthman ibn Affan, the Battle of Siffin resulted in approximately 70,000 casualties and no clear cut winner. The fighting was ended after three days when both sides turned to arbitration to decide the outcome. Despite a peace settlement, the empire remained split until Ali's assassination 661, and Muawiyah's ascension to the caliphate.