While Islamic political institutions were being implemented in Sulu, Muslim traders and possibly itinerant teachers visited the eastern and northern parts of Mindanao Island. The advent of Muhammad Kabungsuwan and his lieutenants developed a system of multiple marriage alliances with various ruling families which served as a means of extending both political control and Islamization. The coming of this intrepid Arab-Malay, to whom the pervasive spread of Islam in Mindanao is attributed, and from whom all the leading sultans of that island have claimed descent, can be calculated to have taken place around the second decade of the sixteenth century. (Majul, 1973)