<P> 1893 map of Bengal </P> <Li> <P> 1831 map of Hindustan showing the then Bengal in green in the north east </P> </Li> <P> 1831 map of Hindustan showing the then Bengal in green in the north east </P> <P> The early Sultans of Bengal ruled until 1282 which was followed by the rule of several successive dynasties . Ilyas Shah founder of the Ilyas Shahi dynasty, took complete charge of the then Bengal and the capital was shifted to Sonargaon (near present day, Dhaka in Bangladesh). He was one of the independent rulers of Bengal . His son, Sikandar Shah, who succeeded him, built the Adina Mosque at Pandua, near Gour, Adina Mosque in the medieval times, was considered to be the largest in undivided Bengal, as well as the entire Indian subcontinent . </P>

Who introduced dual system of government in bengal and why