Mataram conquest of Surabaya in the context of "Duchy of Surabaya"

The Duchy of Surabaya (Indonesian and Javanese: Kadipaten Surabaya) was a Javanese principality centered in Surabaya, on the northeastern coast of Java (in today's East Java, Indonesia), that existed as an independent polity from c. 1546 to 1625. It became independent following the disintegration of the Demak Sultanate, and by the beginning of the 17th century had become the leading power in east Java and the most important port on Java's northeastern coast. Subsequently, it entered into decades of conflict with the Mataram Sultanate that ended in the victory of Mataram and the fall of Surabaya in 1625.