In Lebanon, deadly fighting has broken out—again—between Sunni Muslims loyal to the government and Shiite supporters of Hezbollah. Why do these two groups, that are also creating chaos in Iraq, hate each other so? Some background:

Both Sunnis and Shiites have the Koran (Qur’an) as the source of their beliefs and believe “‘There is but one God, Allah, and Mohammed is His prophet.” The deadly difference concerns who are Mohammed’s rightful successors.

Shiites believe that only those in the bloodline of Mohammed can be in leadership.

Sunnis, who make up 90 percent of Muslims, believe that the leader (imam) of the Muslim community should be selected on the basis of the leader’s individual merits and communal consensus regardless of lineage.

The split occurred after Mohammed’s death in 623 AD when community leaders elected a close companion of the prophet named Abu Bakr to become the first Caliph (Arabic for “successor”). Although most Muslims accepted this decision, some supported the candidacy of Ali ibn Abi Talib, the Prophet’s cousin and son-in-law. Ali’s supporters, now the Shiites, assassinated the third Caliph in 656 AD and made Ali the Caliph. Then, what are now the Sunnis, assassinated Ali in 670 AD, and the deadly division was solidified.

Shiites are most dominant in Iran and Iraq, but represent only about 10 percent of the one billion Muslims. Sunnis are dominant in such countries as Afghanistan, Egypt, Jordan, Indonesia and Saudi Arabia. Only 20 per cent of Muslims are Arab with the world’s largest Muslim-majority country being Indonesia.