Modern Islam is divided into two main branches: the Sunni and the Shia. These sects share the core beliefs of Islam, but the schism between the two was cemented by the politics of the early Muslim world, and by differing interpretations of the Islamic scripture. In this handbook we explore the essential differences between the Sunni and Shia, and examine the roots of the Islamic schism at the ancient Battle of Karbala. Then we investigate the Hidden Imam, the six-year-old descendant of the Prophet who disappeared in 874 A.D., further defining what Shiism would become. We also meet the sub-sects of Shiism, from the dominant “Twelvers” to the secretive Druze. Finally, we tour the holy sites of Shia Islam, and learn how each came to play a part in defining the second largest denomination in Islam.

Shia Muslim clerics hold their heads as they weep while listening to stories about the death of the 7th century Muslim Shia leader Hussein at a prayer meeting in southern Beirut, 2002. (AP Photo/Santiago Lyon)

SOURCES: Sources: Nasr, Vali: “When the Shia Rise.” FOREIGN AFFAIRS, July/August 2006. Armstrong, Karen: ISLAM: A SHORT HISTORY. New York: Modern Library, 2002. ENCYCLOPEDIA BRITANNICA Online, articles: Abbasid Dynasty, Abu Bakr, Alawites, ‘Ali, Ashura, Battle Of Karbala, Bohra, Druze, fitnah, Husayn ibn ‘Ali, Islam, Ismaili, Impact on Isma-illi theology, Ithna ‘Ashariyah, Karbala, Kharjite, Muhammad, Muhammad al-Mahdi al-Hujjah, Mahdi, al-, Sunnite, Shiite, Umayyad, Yazid I, Zaidiyyah, Zakat. Funk and Wagnalls NEW WORLD ENCYCLOPEDIA, articles: Imam, Ismailis, Shiism, Sunnites, Karbala. The Pew Forum on Religion and Public Life: Event transcript.