After a long period of decline and passivity under the later Fatimid caliphs, Egypt once again became the center of a vigorous empire ruled by Salah al-Din (Saladin) and his Ayyubid successors (1171-1250). Around Egypt clustered a rather loose federation of Syrian and Mesopotamian emirates, each governed by a prince of the Ayyubid dynasty, who usually acknowledged the ruler of Egypt as their sultan because of the country’s obvious geopolitical and economic resources.