power in the region in the 17th and 18th centuries had been the Bornu Empire. However, revolutions and the rise of new powers decreased the power of the Bornu empire and by 1759 its rulers had lost control over the oasis town of Bilma and access to the Trans-Saharan trade. Vassal cities of the empire gradually became autonomous, and the result by 1780 was a political array of independent states in the region. The fall of the Songhai Empire in 1591 to Morocco also had freed much of the central Bilad as-Sudan, and a number of Hausa sultanates led by different Hausa aristocracies had grown to fill the void. Three of the most significant to develop were the sultanates of Gobir, Kebbi (both in the Rima River valley), and Zamfara, all in present-day Nigeria. These kingdoms engaged in regular warfare against each other, especially in conducting slave raids. In order to pay for the constant warfare, they imposed high taxation on their citizens. The region between the Niger River and Lake Chad was largely populated with the Fulani, the Hausa, and other ethnic groups that had immigrated to the area such as the Tuareg. Much of the population had converted to Islam in the centuries before; however, local pagan beliefs persisted in many areas, especially in the aristocracy. In the end of the 1700s, an increase in Islamic preaching occurred throughout the Hausa kingdoms. A number of the preachers were linked in a shared Tariqa of Islamic study. Maliki scholars were invited or traveled to the Hausa lands from the Maghreb and joined the courts of some sultanates such as in Kano. These scholars preached a return to adherence to Islamic tradition. The most important of these scholars is Muhammad al-Maghili, who brought the Maliki jurisprudence to Nigeria. Fulani Wars Usman dan Fodio, an Islamic scholar and an urbanized Fulani, had been actively educating and preaching in the city of Gobir with the approval and support of the Hausa leadership of the city. However, when Yunfa, a former student of dan Fodio, became the sultan of Gobir, he restricted dan Fodio's activities, eventually forcing him into exile in Gudu. A large number of people left Gobir to join dan Fodio, who also began to gather new supporters from other regions. Feeling threatened by his former teacher, Sultan Yunfa declared war on dan Fodio on February 21, 1804. Usman dan Fodio