The First Fitna
The First Islamic Civil War (656–661), also called the First Fitna (Arabic: فتنة مقتل عثمان; Transliteration: Fitnat Maqtal Uthmān "The Fitna of the killing of Uthman"), was the first major civil war within the Islamic Caliphate.
It arose as a struggle over who had the legitimate right to become the ruling Caliph. The dispute shattered the unity of the Muslim ummah and resulted in the permanent division of Islam into rival Shi'a and Sunni sects.
The Fitna began as a series of revolts fought against Ali ibn Abi Talib, the fourth and final of the Rightly-Guided Caliphs, caused by the controversial assassination of his predecessor, Uthman Ibn Affan. It lasted for the entirety of Ali's reign, and its end is marked by Muawiyah's assumption of the caliphate (founding the Umayyad dynasty), and the subsequent recorded peace treaty between him and Hassan ibn Ali.