commanded by the royal court. A formidable force could be raised from tributary regions, if necessary. Conversion to Islam was a gradual process. The power of the mansa depended on upholding traditional beliefs and a spiritual foundation of power. Sundiata initially kept Islam at bay. Later mansas were devout Muslims but still acknowledged traditional deities and took part in traditional rituals and festivals, which were important to the Mandé. Islam became a court religion under Sundiata's son Uli I (1225–1270). Mansa Uli made a pilgrimage to Mecca, becoming recognised within the Muslim world. The court was staffed with literate Muslims as secretaries and accountants. Muslim traveller Ibn Battuta left vivid descriptions of the empire. The Mali Empire saw an expansion of learning and literacy. In 1285, Sakura, a freed slave, usurped the throne. This mansa drove the Tuareg out of Timbuktu and established it as a center of learning and commerce. The book trade increased, and book copying became a very respectable and profitable profession. Kankou Musa I founded a university at Timbuktu and instituted a programme of free health care and education for Malian citizens with the help of doctors and scholars brought back from his legendary hajj. Timbuktu and Djenné became important centres of learning within the Muslim world. Mali reached the peak of its power and extent in the 14th century, when Mansa Musa (1312–1337) made his famous hajj to Mecca with 500 slaves, each holding a bar of gold worth 500 mithqal. Mansa Musa's hajj devalued gold in Mamluk Egypt for a decade. He made a great impression on the minds of the Muslim and European world. He invited scholars and architects like Ishal al-Tuedjin (al-Sahili) to further integrate Mali into the Islamic world. After the reign of Mansa Suleyman (1341–1360), Mali began its spiral downward. Mossi cavalry raided the exposed southern border. Tuareg harassed the northern border to retake Timbuktu. Fulani (Fulbe) eroded Mali's authority in the west by establishing the independent Imamate of Futa Toro, a successor to the kingdom of Takrur. Serer and Wolof alliances were broken. In the 15th century, the city-state of Gao to made a bid for independence and regional power. Under the leadership of Sonni Ali (r. 1464–1492), the Songhai of Gao formed the Songhai Empire, which would fill the vacuum left by the Mali Empire's collapse. In 1545 to 1546, the Songhai Empire took Niani. After 1599, the