Middle Ages
The Islamic prophet Muhammad founded Islam in the early 7th century. Soon after his death in 632, Islam split into two main branches: the Sunni Muslims and the Shi'a. Most Muslims (about 85%) are now Sunni. Shi'a live mostly in Iran and Iraq. The Sunni-Shi'a split has been compared to the later East-West Schism of 1054 or the Protestant Reformation within the Western Christianity starting in 1517.