Why a battle against former allies destroyed the authority of the fourth Rashidun caliph
In July 658 CE, Ali ibn Abi Talib faced a brutal dilemma: fight his own former supporters or risk the safety of his people. The resulting Battle of Nahrawan crushed a radical insurgency but left Ali’s military exhausted and his political standing permanently fractured, setting the stage for his eventual assassination.
The conflict originated from the First Fitna, a period of intense instability following the assassination of the third caliph, Uthman ibn Affan, in 656. Ali, Muhammad’s cousin and son-in-law, assumed the caliphate but faced immediate opposition from prominent figures like Aisha and Mu'awiya ibn Abi Sufyan. During the Battle of Siffin in 657, Ali’s army forced him into arbitration with Mu'awiya. A faction of Ali’s soldiers, who believed arbitration was a violation of divine law, defected to form the Kharijites, or 'those who leave.'
Tensions escalated when the Kharijites began executing civilians who refused to denounce Ali and Mu'awiya. Faced with reports of extreme violence, including the murder of a pregnant woman, Ali marched his 14,000-strong army to the Nahrawan Canal to neutralize the threat. Before the fighting began, Ali offered amnesty to any rebel who would surrender or return to Kufa. Approximately 1,200 fighters accepted, leaving 2,800 to face his forces. The battle was decisive; Ali’s archers and cavalry decimated the Kharijite ranks, killing most of the remaining rebels, including their leader, Abd Allah ibn Wahb al-Rasibi.
Despite the military victory, the battle proved a political disaster. Ali’s troops, exhausted and demoralized by the slaughter of fellow Muslims, refused to continue the campaign against Mu'awiya in Syria. The army deserted the mustering ground at Nukhayla, forcing Ali to abandon his plans. This failure weakened his leadership significantly, and in January 661, he was assassinated by a Kharijite dissident. While the Kharijite movement was suppressed in the short term, the Battle of Nahrawan cemented a permanent schism in the early Muslim community, with the group continuing to threaten the state until the 10th century.
Source: Battle of Nahrawan
