of present-day Morocco and Spain. The Berbers increasingly used the traditional trade routes of the Sahara. Caravans transported salt, gold and slaves between North Africa and West Africa, and the control of trade routes became a major ingredient in the constant power struggle between various tribes. On more than one occasion, the Berber tribes of the Western Sahara would unite behind religious leaders to sweep the ruling leaders from power, sometimes founding dynasties of their own. This was the case with the Almoravids of Morocco and Al-Andalus, and was also the case with the jihad of Nasir al-Din in the 17th century and the later Qadiriyyah movement of the Kunta in the 18th century. Zawiyas An important role was played by the zawiyas. As centres of Islamic education under the supervision of an Islamic scholar, the 'saih', they became centres of new communities. In many tribal groups we see a split when a part of their members distanced themselves from the traditional leading group and formed a zawiya, following the Islamic example. These newly formed communities separated themselves from traditional, military society. Until then matrilinear ancestry had been important. They stressed the importance of patrilinear ancestry in which they tried to show their descent from the Islamic prophet Muhammad (the Shurfa), his tribe (the Quraysh) or his companions (Ansar). They put spiritual ideals higher than the ideals of battle. They preferred religious influence over military pressure, equal membership over dependency. They were in favour of giving alms and lending cattle to people in need and were vehemently opposed to plunder and extortion. They declared cattle-raids and random taxing to be unlawful. Although they were opposed to non-religious warfare, they were strong enough to defend themselves against military attacks. These zawiya tribes became the tribes of the teachers, specialists of religion, law and education. Arabization of the mujahideen (13th and 14th century) In the time of the Almoravids professional warriors had fought as mujahideen in their holy war. Just like the people who had united in zawyas, the mujahideen began to form tribes based on their specific occupations. This development was accelerated by the arrival of Maqil Arab tribes. In the 13th and 14th century, these tribes migrated westwards along the Sahara's northern border to settle in the Fezzan (Libya), Ifriqiya (Tunisia), Tlemcen (Algeria), Jebel Saghro (Morocco), and Saguia el-Hamra (Western Sahara). When the Maqil Arabs arrived in the western part