Alauddin Husain Shah of Gaur removed Nilambar of the Khen dynasty in 1498, occupied Kamata and placed his son Danyal Husayn in charge.

[13] As part of these alliances Hajo's daughter Hira married Hariya Mandal, a member of the Mech tribe from Chiknagram in present-day Kokrajhar district,[14] though these ethnic identities are difficult to discern since there were frequent intermarriages.

[15][16] Bisu, born to Hariya and Hira,[17] acquired the political legacy of his grandfather Hajo[18] and established himself as the chief of the eastern branch of the Koches in the Khuntaghat region (present-day Kokrajhar district of Assam).

[19][20] It is thought that Bisu fought under the leadership of the Bhuyans as a landlord against the occupation of Kamata kingdom by Alauddin Husain Shah and thus learned their military tactics.

[34] Later, Brahman pundits created a legend that lord Siva was the father of Biswa Singha to give legitimacy to his rule[35] and conferred on him the status of the Kshatriya varna.

[36] According to the legend constructed at the time of coronation, Bisu was son of Siva and his tribe either the Koch or Mech people were Kshatriyas who ran away from the fear of extermination by the Brahman sage Parashurama and took shelter in Western Assam and Northern Bengal and later disguised themselves as Mlechchas.

During the reign of Nara Narayan, Koch Behar saw the propagation of eksarana-namadharma by Sankardev along with his two disciples Madhavdeva and Damodardev,[41][42] which helped brought a cultural renaissance to the kingdom.

[43] The spread of this new religious movement was initially resisted by the Koch, Mech and Kachari people residing in the Koch-Kamata kingdom,[44][4] for which Nara Narayan made an official order to recognise the different religious practices of the people residing in the kingdom,[45] though by the end of the 18th century, the masses of the Koch population had absorbed considerable Hindu content.

The Ahom king, Prataap Singha, then established Balinarayan as a vassal in the newly acquired region between Barnadi and Bharali rivers, and called it Darrang.

The Koch rule began with the appointment of Kamal Narayan (step-brother of Chilarai and Naranarayan) as the Dewan a couple of years after the establishment of the garrison.