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.
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.