	Historical Background

The differences between the Sunni and Shiite Islamic sects are rooted in disagreements over the succession to the Prophet Muhammad, who died in 632 AD, and over the nature of leadership in the Muslim community. The use of violence by members of a given religious sect may be motivated by secular political goals or individual factors. Core Beliefs and Shared Practices

Although there are considerable differences between Sunni and Shiite Islam, the two Islamic sects share common traditions, beliefs, and doctrines. This premise has been inconsistently practiced within the Sunni Muslim community throughout history. Following the 1979 Soviet invasion of Afghanistan and Shiite Islamic revolution in Iran, Saudi Arabia's ruling Sunni royal family began allowing their clerics and citizens to more actively promote Saudi religious doctrine abroad, and Saudi individuals and organizations since have financed the construction of mosques, religious schools, and Islamic centers in dozens of countries. Shiite Islam: Development and Basic Tenets

Initially, the Shiite movement gained a wide following in areas that now include Iraq, Iran, Yemen, and parts of Central and South Asia. Today, according to some estimates, Shiite Islam is practiced among approximately 10% to 15% of the world's Muslim population. Alawites exist mostly in Syria and Lebanon.
The majority of the world's Muslim population follows the Sunni branch of Islam, and approximately 10%-15% of all Muslims follow the Shiite (Shi'ite, Shi'a, Shia) branch. Shiite populations constitute a majority in Iran, Iraq, Bahrain, and Azerbaijan. There are also significant Shiite populations in Afghanistan, Kuwait, Lebanon, Pakistan, Saudi Arabia, Syria, and Yemen. Sunnis and Shiites share most basic religious tenets. However, their differences sometimes have been the basis for religious intolerance, political infighting, and sectarian violence.
This report includes a historical background of the Sunni-Shiite split and discusses the differences in religious beliefs and practices between and within each Islamic sect as well as their similarities. The report also relates Sunni and Shiite religious beliefs to discussions of terrorism and sectarian violence that may be of interest to Congress. Also see CRS Report RS21695, The Islamic Traditions of Wahhabism and Salafiyya, by [author name scrubbed].