In 656 A.D., the fourth Caliph, a man by the name of Ali, was elected as ruler of Islam. Ali came to power when his predecessor was murdered.
The governor of Syria, Mu’ Awiyah, was the nephew of Uthman, the former, and now murdered, caliph. Mu’ Awiyah accused Ali of planning the murder of his uncle so that he could take power for himself.
The supporters of Mu’ Awiyah fought for several years against the supporters of Ali for control of the government. In 661 A.D., Ali was murdered by one of his own followers, ending the civil war.
Mu’ Awiyah was now the undisputed ruler of Islam. The followers of Ali were upset at their loss, and refused to accept the rule of Mu’ Awiyah. Instead, they installed the son of Ali as their leader, a man by the name of Husayn.
Those who followed Husayn became known as the Shiite Muslims, while those who remained faithful to Mu’ Awiyah were known as the Sunni Muslims.