First Fitna
Background

Battle of Nahrawan
Following the Battle of Siffin, a group separated from Ali when he agreed to settle the dispute with Mu'awiya through arbitration, a move considered by the group as against the Quran. Most of them had pressured Ali to accept the arbitration, but subsequently reversed course and declared that the right to judgment belonged to God alone. While Ali largely succeeded in regaining their support, the remaining opponents of arbitration gathered in Nahrawan, on the east bank of the Tigris. Due to their exodus, this group became known as the Kharijites, from the Arabic for "to go out" or "to rise in revolt".
Battle of Nahrawan
!The [Nahrawan Canal ran parallel to the east bank of the Tigris.](//upload.wikimedia.org/wikipedia/commons/thumb/c/ce/IraqundertheAbbasidCaliphate%28cropped%29.png/250px-IraqundertheAbbasidCaliphate%28cropped%29.png)