The Battle of Siffin was fought in 657 CE between the Iraqi Arab forces of the fourth Rashidun caliph Ali ibn Abi Talib and the Syrian Arab forces of the rebelling long-time governor of the Levant, Mu'awiya ibn Abi Sufyan. The battle is named after its location Siffin on the banks of the Euphrates river. The fighting stopped after the Syrians called for arbitration when Ali's forces had gained the upper hand, to which Ali reluctantly agreed under pressure from some of his troops. The arbitration process ended inconclusively in 658 though it strengthened the Syrians' support for Mu'awiya and his political position while weakening the authority of Ali and causing dissension among the Iraqis. The battle was part of the First Fitna and is considered a major step towards the establishment of the Umayyad Caliphate.