With the takeover of Egypt from the Fatimids by Saladin, the Kurdish lieutenant of a Seljuk Turkish dynasty, the Seljuk invasion and conquest of the Middle East reached its maximum extent. In Egypt itself, the takeover exemplified Weber's model of the patrimonial state,when the military finally abolished the dynasty they had served, and took its place. In the world at large, it proved to be the beginning of the end for the Caliphal principle which over the past five hundred years had inspired the imperial dynasties which laid claim to the empire of Islam. The invasions of the old Arab empire by the Seljuks and the Crusaders in the eleventh century were followed in the thirteenth by the invasions of the Mongols in the east and the Christians of northern Spain in the west, which between them put an end to the 'Abbasid Caliphate at Baghdad and precipitated the downfall of the Almohads in North Africa. The Ayyubids, the descendants of Saladin, were themselves replaced in Egypt and Syria by the colonels of their regiments, the founders of the Mamluk Sultanate. The Almohad empire in North Africa was divided between a reconstituted Ifriqiyan state ruled from Tunis, and a successor state in Morocco, ruled from Fes;Tlemcen in western Algeria became the capital of a third dynasty. Over the next two hundred and fifty years, the emergence of this line of states to the north of the Sahara was matched to the south by the formation of polities of one kind or another as far away as the Zimbabwean plateau in the first centuries of Oliver and Atmore's Medieval Africa, 1250–1800.