Tranquillity disappeared with later Fatimid rulers, who could not control their unruly regiments of Berber and Sudanese soldiers. A low Nile caused serious famine in 1065. New danger appeared with the First Crusade from western Europe, which established Christian control over Syria and Palestine in the late 1090s. The Fatimid caliphs, by now pawns in the hands of their generals, appealed to Nur ad-Din of Halab (Aleppo), and he sent an army to help them against the Crusaders in 1168. Saladin, one of Nur ad-Din's generals, was installed as vizier. In 1171 he abolished the Fatimid caliphate, founding the Ayyubid dynasty and restoring Sunni rule to Egypt. Saladin reconquered most of Syria and Palestine from the Crusaders and became the most powerful Middle Eastern ruler of this time. His nephew, Sultan al-Kamil, who reigned 1218-1238, successfully defended Egypt against a Christian attack in 1218-1221, but after his death Ayyubid power declined. The Ninth Crusade, led by Louis IX of France, was repelled in 1249, with the aid of the Mamelukes, slave troops in Ayyubid service. The following year the Mamelukes overthrew the Ayyubids and established their own ruling house.