Mali, like Ghana, was built on gold. While Ghana had been under attack by the Arabs from outside, various peoples from within struck for their own freedom. The Mandinka people, who had been the middlemen in the gold trade and who had received protection from the king of Ghana, achieved their independence in 1230 A.D. They went on to use their position in the gold trade to build an empire of their own. The peak of their influence and power was achieved in the early fourteenth century under Mansa Kankan Musa who ruled Mali for a quarter of a century. He extended its boundaries beyond those of Ghana to include such important trading cities as Timbuktu and Gao, encompassing an area larger than that controlled by the European monarchs of that day. This empire also was based on its ability to provide stable government and a flourishing economy. An Arab traveler, Ibn Batuta, shortly after Musa's death, found complete safety of travel throughout the entire empire of Mali. Mansa Musa and, for that matter, the entire ruling class of Mali had converted to Islam. This intensified the contacts between West Africa and the Islamic world. Although several of these kings made pilgrimages to Mecca, the most spectacular was the one by Mansa Musa in 1324. On his way there, he made a prolonged visit to Cairo. While there, both his generosity in giving lavish gifts of gold to its citizens and his extravagant spending poured so much gold into the Cairo market that it caused a general inflation. It was estimated by the Arabs that his caravan included some sixty thousand people and some five hundred personal slaves. Mansa Musa took a number of Arabic scholars and skilled artisans back to West Africa with him. These scholars enhanced the university of Timbuktu which was already widely known as a center of Islamic studies. Now, besides exchanging material goods, West Africa and the Arabs became involved in a steady exchange of scholars and learning. The success of Mali in bringing law and order to a large portion of West Africa was responsible for its decline. Having experienced the advantages of political organization, many localities sought self-government. In fact, Mansa Musa had overextended the empire. A skilled ruler like himself could manipulate it, but those who followed were not adequate to the challenge. Movements for self-government gradually eroded central authority until by 1500 Mali had lost its importance as an empire. Although the period of its power and prosperity was respectable by most world empire standards, it was short-lived compared to the history of the previous empire of Ghana. Again, a new empire was to emerge from the ruins of the previous one.