For centuries after the first Arabs passed through North Africa, the presence of Arabic culture in the Western Sahara was limited to scholars and mystics. Then, in the Middle Ages, came a small band of Yemeni tradesmen who came to dominate the desert trade routes. Their descendents, Awlad Hassan, imposed themselves on the native Berbers, introducing a new society, language and religion. Drawing on numerous sources, H.T.Norris examines how the tribes of West Africa responded to the arrival of the Arabs, particularly from the 13th to the 17th centuries.