Bokainagar Fort situated 12 miles east of mymensingh town on the eastern bank of the Balua River (a branch of the Brahmaputra), is now in ruins. A connecting stream of the Balua flowed east to west through the fort.

No historical evidence regarding the origin of Bokainagar fort has been found. The legend is that a Koch chief named Bokai constructed the fort when the ancient kingdom of Kamarupa began to disintegrate in the 15th century. The fort is said to have been named after him. According to another legend, Majlish Khan Humayun, a representative of Sultan Saifuddin Firuz Shah II (1486 - 1489), built the fort. In 1495, when the fort came under husain shah's control, he appointed his son Nusrat to command it. Later, after being defeated by the Mughals, usman khan afghan fled from Orissa, took refuge under isa khan, and became established as a feudal lord of Bokainagar. He rebuilt the fort, established it as a powerful military base, and resisted the Mughals valiantly. Ultimately, however, islam khan defeated him in November 1611 and the fort finally came under Mughal occupation.

Bokainagar fort was one mile long, east to west, and half a mile wide. The fort was protected with a high earthen wall and was surrounded externally by a deep moat. Khwaja Usman's residence is reported to have been situated in the southwestern part of the fort. Innumerable brickbats, part of the southern wall and the crumbling southeastern bastion are all that now remain of the fort. [Shahnaj Husne Jahan]