Of all the tribes and kingdoms Ahoms captured in the formative days of the Empire, the Chutiya Empire fought the longest and hardest war, giving way after almost two centuries of fight. With the collapse of the central authority, people scattered in all directions – Dimapur, where the court retreated, Kachari Dwars on the Bhutan border, Garo Hills and elsewhere. The traditional account of the scattering goes this. However, it is worth noting that the Kachari Empire is as old as, if not older than Chutiya Empire and it’s possible both the royal families are related and the dynasties merged. Or it can mean shift to another capital city.
Long, long ago the Dimas fought against a very powerful tribe (the Ahoms), and being beaten in a great pitched battle, the king with all his forces retreated. But presently further retreat was barred by a wide and deep river, which could in no way be crossed. The Raja, being thus stopped by a river in front and an enemy behind, resolved to fight once more the next day, unless the problem of crossing the river could be solved. With this determination he went to sleep and had a dream in which a god appeared to him and promised to help him. The god said that early next morning the king with all his people must boldly enter the river at a spot where he would see a heron standing in the water, and walk straight across the river, but no one must look back. Next morning a heron was found, sure enough, standing in the water near the bank; and the king, remembering his dream, led his people to the spot and went into the water, which they found had shoaled enough to form a ford and allow them to wade across. In this way he crossed with a great part of his people. But still all had not crossed. There were some on the other bank and some in the middle of the river, when a man among the latter wondering whether his son was following him, looked back, with the result that the water at once got deep and every one had to save himself as best he could ; while the men on the other bank, having no chance of crossing, dispersed. They who were caught in the middle of the river had to swim for their lives, and were washed down to different places. Some saved themselves by catching hold of Khagris (rushes) growing on the bank, and are to this day called Khagrdbaria. Others caught hold of nals (or reeds) and are thus called Nalbarias. The Dimasa are the people who crossed in safety.