In Morocco by Edith Wharton — Read

While the Hilalian Arabs were conquering and destroying northern Morocco another but more fruitful invasion was upon her from the south. The Almoravids, one of the tribes of Veiled Men of the south, driven by the usual mixture of religious zeal and lust of booty, set out to invade the rich black kingdoms north of the Sahara. Thence they crossed the Atlas under their great chief, Youssef-ben-Tachfin, and founded the city of Marrakech in 1062. From Marrakech they advanced on Idrissite Fez and the valley of the Moulouya. Fez rose against her conquerors, and Youssef put all the male inhabitants to death. By 1084 he was master of Tangier and the Rif, and his rule stretched as far west as Tlemcen, Oran and finally Algiers.

His ambition drove him across the straits to Spain, where he conquered one Moslem prince after another and wiped out the luxurious civilization of Moorish Andalusia. In 1086, at Zallarca, Youssef gave battle to Alphonso VI of Castile and Leon. The Almoravid army was a strange rabble of Arabs, Berbers, blacks, wild tribes of the Sahara and Christian mercenaries. They conquered the Spanish forces, and Youssef left to his successors an empire extending from the Ebro to Senegal and from the Atlantic coast of Africa to the borders of Tunisia. But the empire fell to pieces of its own weight, leaving little record of its brief and stormy existence. While Youssef was routing the forces of Christianity at Zallarca in Spain, another schismatic tribe of his own people was detaching Marrakech and the south from his rule.