The Sunni-Shia split within Islam originates from controversy
surrounding Ali, cousin of the Prophet Mohammed.
All Muslims respect Ali as the second historical follower of
Islam, but whilst Sunnis believe he was just one of several possible
leaders, Shia believe he and his line were divinely appointed.
Shia Islam recognises Ali as the first of the Twelve Imams, a
divinely-ordained dynasty of supreme religious rulers, related by
blood to the Prophet. Although the line ended in 873, Shia Muslims
do not believe the final Imam is dead, but instead is 'hidden' - and
liable to return.
Sectarian violence began when Ali was installed, and civil war
broke out over the instillation of a 'rightful' caliph in the wake
of Ali's reign. The intensity of fighting gradually decreased until
the twentieth century, when the break up of the Ottoman Empire, two
gulf wars and a Shia revolution helped reignite tension.
Sunni Islam does not have a formal clergy, unlike Shia which is
structured according to a religious hierarchy, culminating in a
religious ruler, such as The Grand Ayatollah in Iran.
Many Sunnis believe that to instil a human, like the Supreme
Imam in Iran, with divine influence is wrong.
Approximately ninety per cent of the Muslim world is Sunni.