The Battle of Siffin (Arabic: ; May-July 657 CE) occurred during the First Fitna, or first Muslim civil war, with the main engagement taking place from July 26 to July 28. It was fought between Ali ibn Abi Talib and Muawiyah I, on the banks of the Euphrates river, in what is now Ar-Raqqah, Syria. Following the controversial murder of Uthman ibn Affan, Ali had become Caliph but struggled to be accepted as such throughout the Muslim Empire. Muawiyah, the governor of Syria, was a kinsman of the murdered Caliph, and wanted the murderers brought to justice. He considered that Ali was unwilling to do this, and so Muawiyah rebelled against Ali, who attempted to put down the rebellion. The result was the engagement at Siffin. However, the battle was indecisive, and the two parties agreed to an arbitration, which was equally indecisive. The battle and arbitration served to weaken Ali's position, but did not resolve the tensions that were plaguing the empire. To the Shia, Ali ibn Abi Talib