In the 9th century, Arab Muslims established commercial as well as religious contacts within the region before the conquest, mainly through the coastal regions as traders and primarily via the ports of Chittagong. Arab navigation in the region was the result of the Muslim reign over the Indus delta. Following the conquests of Muhammad bin Bakhtiyar Khalji and the establishment of the Delhi Sultanate, Indian Islamic missionaries achieved their greatest success in terms of successful dawah and number of converts to Islam in Bengal. Shah Jalal is thought to have spread Islam in the north-eastern Bengal and Assam during the beginning of the 12th century. The Islamic Bengal Sultanate, a major trading nation in the world, was founded by Shamsuddin Ilyas Shah after its independence from the Tughlaq dynasty. Subsequently, Bengal was conquered by Babur, the founder of one of the gunpowder empires, but was also briefly occupied by the Suri Empire.