During a period between about 1576 CE to 1605 CE, the Delhi Mughal power waged a 30-year long war against its Pathan foes who settled in Bengal/Bihar after their defeat in the 1st Battle of Panipat in 1526 CE.
The Raja of Koochbehar took the opportunity during this long war and sent his troops to occupy lands in its south and advanced towards Bogra after occupying Greater Rangpur and Dinajpur districts.
Sultan Daud Khan Karrani (son of Taj Khan Karrani) of Bengal was already killed by the Mughal troops somewhere near Subarnarekha river in Orissa in 1576 after which Bengal had no central power to offset the Mughal advance. It became a loose confederation ruled by multiple Dukes.
The advances made by the Kuchbehar troops alarmed Lord Isa Khan Afghan of Kotravu/Narayanganj. He led troops to the north to challenge Kuchbehar which was forced to vacate all the lands it had occupied.
A peace treaty was signed between the parties the map of which was yet to be finalized when intelligence reached Isa Khan that the Mogh/Arakanese pirates had entered the Padma river and were moving towards his Capital Kotravu.
So, he rushed back to his Capital without finalizing the map. This is how the map remained a very unnatural and complicated one before a BD-India agreement was signed. BD land was inside India and an Indian land within it, and vice versa.
The commentator picked the gambling stories circulating among the border locals who know nothing about the historical background.
* For details please read the following History book:
GOUR KAHINI গৌড় কাহিনী
by
GHOSH, SHAILENDRA KUMAR