In Morocco by Edith Wharton — Read

The Beni-Merins or Merinids were nomads who ranged the desert between Biskra and the Tafilelt. It was not a religious upheaval that drove them to the conquest of Morocco. The demoralized Almohads called them in as mercenaries to defend their crumbling empire; and the Merinids came, drove out the Almohads, and replaced them.

They took Fez, Meknez, Sale, Rabat and Sidjilmassa in the Tafilelt; and their second Sultan, Abou-Youssef, built New Fez (Eldjid) on the height above the old Idrissite city. The Merinids renewed the struggle with the Sultan of Tlemcen, and carried the Holy War once more into Spain. The conflict with Tlemcen was long and unsuccessful, and one of the Merinid Sultans died assassinated under its walls. In the fourteenth century the Sultan Abou Hassan tried to piece together the scattered bits of the Almohad empire. Tlemcen was finally taken, and the whole of Algeria annexed. But in the plain of Kairouan, in Tunisia, Abou Hassan was defeated by the Arabs. Meanwhile one of his brothers had headed a revolt in Morocco, and the princes of Tlemcen won back their ancient kingdom. Constantine and Bougie rebelled in turn, and the kingdom of Abou Hassan vanished like a mirage. His successors struggled vainly to control their vassals in Morocco, and to keep their possessions beyond its borders.