The separation of Muslims into Sunni and Shia dates back to the death of Muhammad in AD 632. Shias believe that Ali, who was Muhammad’s cousin and son-in-law, should have been Muhammad’s successor. Instead, Abu Bakr, Muhammad’s faithful friend and father-in-law, was chosen and became the first of the ‘rightly guided caliphs’.
Ali was chosen later as the fourth caliph in AD 656, but his followers disagreed and so the Muslim community split. Shias believed that a direct relative of Muhammad should be the leader and some espouse that Muhammad himself had dictated that Ali should be his successor.
Over time, both Sunni and Shia Muslims developed their own theology, groupings and creeds. Shia Islam is more authoritarian in structure, looking to one supreme leader, whereas Sunni Islam is more diverse, with each country having its own religious leaders.
Today, about 85 percent of Muslims are Sunni. Some countries have outlawed Shia Islam while others discriminate severely against Shia Muslims. Because of this, Shia Muslims have a strong sense of suffering. Sunni Muslims are the majority in most Muslim countries, except in parts of Iraq, Lebanon and Bahrain, as well as in all of Iran.