<P> Qadis worked at the local level and were positioned in important trading towns, such as Timbuktu and Djenné . The Qadi was appointed by the king and dealt with common - law misdemeanors according to Sharia law . The Qadi also had the power to grant a pardon or offer refuge . The Assara - munidios, or "enforcers" worked along the lines of a police commissioner whose sole duty was to execute sentencing . Jurists were mainly composed of those representing the academic community; professors were often noted as taking administrative positions within the Empire and many aspired to be qadis . </P> <P> Upper classes in society converted to Islam while lower classes often continued to follow traditional religions . Sermons emphasized obedience to the king . Timbuktu was the educational capital . Sonni Ali established a system of government under the royal court, later to be expanded by Askia Muhammad, which appointed governors and mayors to preside over local tributary states, situated around the Niger valley . Local chiefs were still granted authority over their respective domains as long as they did not undermine Songhai policy . </P> <P> Tax was imposed onto peripheral chiefdoms and provinces to ensure the dominance of Songhai, and in return these provinces were given almost complete autonomy . Songhai rulers only intervened in the affairs of these neighboring states when a situation became volatile, usually an isolated incident . Each town was represented by government officials, holding positions and responsibilities similar to today's central bureaucrats . </P> <P> Under Askia Muhammad, the Empire saw increased centralization . He encouraged learning in Timbuktu by rewarding its professors with larger pensions as an incentive . He also established an order of precedence and protocol and was noted as a noble man who gave back generously to the poor . Under his policies, Muhammad brought much stability to Songhai and great attestations of this noted organization are still preserved in the works of Maghrebin writers such as Leo Africanus, among others . </P>

Under whose reign did songhai become the largest empire in african history