The military history of Bassein encompasses the period from 1526 when the portuguese established their first factory at Bassein until 1818 when Bassein lost its strategic importance following the defeat of Marathas by the British. Bassein (Vasai) town was part of the territory of the Hindu Devagiri Yadavas until 1317, and it later became a seaport for the Gujarat Muslim kings. In 1526, the Portuguese established a fort (now in ruins) and trading station at Bassein, and the town became famous for its shipbuilding industry.
Bassein renamed Vasai after Indian independence is a small coastal town north of Mumbai. It was historically known to the portuguese as back in medieval Bassein had a great strategic value for the portuguese and maintaining their command of the Arabian sea.