First Fitna participant Alī ibn Abī Ṭālib
The First Fitna was the first civil war in the Islamic community. It led to the overthrow of the Rashidun Caliphate and the establishment of the Umayyad Caliphate. The civil war involved three main battles between the fourth Rashidun caliph, Ali, and the rebel groups.
The roots of the first civil war can be traced back to the assassination of the second caliph, Umar. Before he died from his wounds, Umar formed a six-member council which elected Uthman as the next caliph. During the final years of Uthman's caliphate, he was accused of nepotism and killed by rebels in 656. After Uthman's assassination, Ali was elected the fourth caliph. Aisha, Talha, and Zubayr revolted against Ali to depose him. The two parties fought the Battle of the Camel in December 656, from which Ali emerged victorious. Afterward, Mu'awiya, the incumbent governor of Syria, declared war on Ali ostensibly to avenge Uthman's death. The two parties fought the Battle of Siffin in July 657, which ended in a stalemate and arbitration. This arbitration was resented by the Kharijites, who declared Ali, Mu'awiya, and their followers infidels. Following Kharijite violence against civilians, Ali's forces crushed them in the Battle of Nahrawan. Soon after, Mu'awiya also seized control of Egypt with the aid of Amr ibn al-As.
In 661, Ali was assassinated by the Kharijite Abd al-Rahman ibn Muljam. After Ali's death, his heir Hasan was elected caliph and soon after attacked by Mu'awiya. The embattled Hasan concluded a peace treaty, acknowledging the rule of Mu'awiya, who subsequently founded the Umayyad Caliphate and ruled as its first caliph.