At the helm of the Mamluk institution was the sultan, himself a Mamluk, whose skills had marked him out for leadership among his peers. Every Mamluk sultan, irrespective of his individual ambitions, activities and interests, had certain overriding responsibilities inherent to his office. Most immediately, he was the supreme champion and defender of Sunni (Orthodox) Islam, protector of the Holy Cities and sites within the empire and guardian of the Islamic Caliphate, which thanks to Mamluk intervention was re-established in Cairo in 659 / 1261, after Baghdad had fallen to the Mongols three years earlier.