The word caliph comes from the Arabic khalifa, meaning successor, and for close to thirteen centuries it named the men who claimed to inherit the Prophet Muhammad's authority after his death in 632 AD. This three-part Al Jazeera series traces that title from the first caliphs who built an empire stretching from Arabia across three continents, through the Sunni-Shia split that grew out of disputes over rightful succession, to the Ottoman caliphate's collapse when the Turkish Republic abolished the office in 1924. Scholars of Islamic history narrate each stage, explaining how the caliphate functioned as both religious and political authority and why its end scattered that claim to leadership across competing movements. The series closes on a contemporary note, recalling how ISIL declared Abu Bakr al-Baghdadi a caliph in 2014, a proclamation the overwhelming majority of Muslims rejected. Director Husein Alrazzaz keeps the focus on how a fourteen-hundred-year-old title kept getting fought over long after the empire it named had disappeared.