The Battle of Siffin was fought in 657 CE (37 AH) between Ali ibn Abi Talib, the fourth of the Rashidun Caliphs and the first Shia Imam, and Mu'awiya ibn Abi Sufyan, the rebellious governor of Syria. The battle is named after its location Siffin on the banks of the Euphrates. The fighting stopped after the Syrians called for arbitration to escape defeat, to which Ali 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 weakened the position of Ali. The battle is considered part of the First Fitna and a step towards the establishment of the Umayyad Caliphate.