short. In the 11th century the conquests initiated by Gijimasu of Kano culminated in the birth of the first united Hausa Nation, although it was short-lived. During the reign of King Yaji I (1349–85) Islam was first introduced to Kano. Many Muslim traders and clerics used to come from Mali, from the Volta region, and later from Songhay. King Yaji appointed a Qadi and Imam as part of the state administration. Muhammad Rumfa (1463–99) built mosques and madrassahs. He also commissioned Muhammad al-Maghili to write a treatise on Muslim governance. Many other scholars were brought in from Egypt, Tunis, and Morocco. This turned Kano into a center of Muslim scholarship. Islamization facilitated the expansion of trade and was the basis of an enlarged marketing network. The 'Ulama provided legal support, guarantees, safe conducts, introductions and many other services. By the end of the fifteenth century, Muhammad al-Korau, a cleric, took control of Katsina declaring himself king. 'Ulama were later brought in from North Africa and Egypt to reside in Katsina. An 'Ulama class emerged under royal patronage. The Hausa rulers fasted Ramadan, built mosques, kept up the five obligatory prayers, and gave alms (zakat) to the poor. Ibrahim Maje (1549–66) was an Islamic reformer and instituted Islamic marriage law in Katsina.Generally Hausaland remained divided between the Muslim cosmopolitan urban elite and the local animistic rural communities. During this time period, Leo Africanus briefly mentions in his book Descrittione dell’Africa descriptions of the political and economic state of Hausaland during that time although it is unknown if he actually visited it; Hausaland seems to have been mostly of a tributary status by Songhai as in his description of Zamfara he comments that "their king was slaughtered by the Askiya and themselves made tributary" and the same is said for the rest of the region. Fall Despite relatively constant growth from the 15th century to the 18th century, the states were vulnerable to constant war internally and externally. By the 18th century, they were economically and politically exhausted. Famines became very common during this period and the Sultans engaged in heavy taxation to fund their wars. Though the vast majority of its inhabitants were Muslim, by the 19th century, they were conquered by a mix of Fulani warriors and Hausa peasantry, citing syncretism and social injustices. By 1808 the Hausa states were finally conquered by Usuman dan Fodio and incorporated into the