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In 680, near Karbala in Iraq, a man was killed in the desert. His name was Husayn, and he was the grandson of the Prophet Muhammad. His death was a crucial episode in the growing split between two groups of Muslims - who would come to be known as the Sunni and the Shia.
And yet this dispute did not begin violently. Arguably, it was not at first a political or theological schism either, but a personal disagreement. And the two groups agree on many of the fundamentals of the religion.
So how did this profound split develop?
Contributors
Amira Bennison, Senior Lecturer in Middle Eastern and Islamic Studies at the University of Cambridge
Robert Gleave, Professor of Arabic Studies at the University of Exeter
Hugh Kennedy, Professor of Arabic in the School of Oriental and African Studies at the University of London