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 major step towards the establishment of the Umayyad Caliphate. Location The battlefield was located in Siffin, a ruined Byzantine-era village at the right bank of the Euphrates in the vicinity of Raqqa in present-day Syria. It has been identified with the modern village of Abu Hureyra in the Raqqa Governorate. Background Opposition to Uthman Ali frequently accused the third caliph, Uthman, of deviating from the Quran and the Sunna, and was joined in his criticism by most of the senior companions of the Islamic prophet Muhammad, including Talha and Zubayr. Uthman was also widely accused of nepotism, corruption, and injustice, and Ali is known to have protested his conduct, including his lavish gifts for his kinsmen, the Umayyads. Ali also protected outspoken companions, such as Abu Dharr al-Ghifari and Ammar ibn Yasir, from Uthman. Ali appears in early sources as a restraining influence on Uthman without directly opposing him. Some supporters of Ali were also part of the opposition to Uthman, joined in their efforts by Talha and Zubayr, and by Aisha, a widow of Muhammad. The last was critical of Uthman for religious innovations and nepotism, but also objected to him for reducing her pension. Among the supporters of Ali were Malik al-Ashtar () and other religiously-learned (). These wanted to see Ali as the next caliph, though there is no evidence that he communicated or coordinated with them. Ali is also said to have rejected the requests to lead the rebels, although he might have sympathized with their grievances, and was thus considered a natural focus for the opposition, at least morally. It is also likely that some companions supported the protests with the hope of either deposing Uthman, or changing his policies, thus underestimating the severity of the opposition to Uthman.