Shi’a Islam is the second largest branch of the tradition, with up to 200 million followers who comprise around 15 percent of all Muslims worldwide, including approximately 90 percent of the Iranian population. Shi’ism differs from Sunni Islam in holding that rightful religious and political leadership of the Muslim community belongs to Muhammad’s family and descendants, who are properly able to interpret sharia (Islamic law) and decipher the Qur’an’s esoteric teachings. The origins of Shi'ism go back to the years after Muhammad’s death in 633 CE when his cousin and son-in-law, Ali, was initially passed over for leadership of the community. Ali eventually became caliph but was assassinated in 661 CE and much of his family—including his son, Husayn—was killed during the power struggle that ensued. For all Shi’ites Ali was the first imam—the divinely chosen and infallible leader of the Muslim community—most Shi'ites (known as Twelvers) believe he was followed by another eleven imams. The last of these imams, Muhammad al-Mahdi, is believed to be in a state of hiding—known as the Occultation—until his triumphant return at the end of time.
Shi’a Islam is the predominant religion in Iran, Iraq, Azerbaijan, and Bahrain, with large populations in Lebanon, Yemen, and Kuwait. It is distinct from Sunni Islam in several respects. Its clerical structure is more formal and hierarchical and it has a rich tradition of esoteric interpretation of the Qur'an that goes beyond scripture’s apparent surface meanings. Throughout history, the considerable authority afforded to leading religious leaders within Shi'ism has translated into clerical political influence and, in some cases, theocracy. Today's Iran is a prominent example. The model set by its founding figures, Ali and Husayn, has given Shi’a Islam a special reverence for martyrdom. Since the early days of Islam, the Sunni majority have often viewed the Shi’a as a splinter group and a threat, spurring persecution that continue to this day in many countries.