The Second Siege of Diu was a siege of the Portuguese Indian city of Diu by the Gujarat Sultanate in 1546. It ended with a major Portuguese victory.At the beginning of 1500s, the Muslim Sultanate of Gujarat was the principal seapower in India. Gujarat fought the Portuguese fleets in collaboration with the Mamluks. The Portuguese were defeated by a combined Mamluk-Gujarati fleet in 1508, which was in turn destroyed by a Portuguese fleet in the Battle of Diu (1509). By 1536, the Portuguese had gained complete control of Diu, while Gujarat was under attack from the Mughals.