In the 12th century the weakness of the Fatimids became so severe that under the last Fatmid Caliph, al-'Adid, they requested help from the Zengids to protect themselves from the King of Jerusalem, Amalric, while at the same time attempting to collude with the latter to keep the Zengids in check. In 1168, as the Crusaders marched on Cairo, the Fatimid vizier Shawar, worried that the unfortified city of Fustat would be used as a base from which to besiege Cairo, ordered its evacuation and then set the city ablaze. While historians debate the extent of the destruction (as Fustat appears to have continued to exist after this), the burning of Fustat nonetheless marks a pivotal moment in the decline of that city, which was later eclipsed by Cairo itself. Eventually, Salah ad-Din (Saladin), a Zengid commander who was given the position of al-'Adid's vizier in Cairo, declared the end and dismantlement of the Fatimid Caliphate in 1171. Cairo thus returned to Sunni rule, and a new chapter in the history of Egypt, and of Cairo's urban history, opened.