Explanation:

After Nara Narayana died in 1587, the Koch kingdom (ensconced between the Mughal Empire in the west/south and Ahom kingdom in the east) was divided into the western Koch Bihar and the eastern Koch Hajo, ruled by his son Lakshimi Narayan and nephew Raghudev respectively. These two kingdoms were bitter rivals. In due course the Mughals formed an alliance with Lakshmi Narayan and the Nawab of Dhaka, a governor of the Mughals attacked Parikshit Narayan, the son of Raghudev in 1602 at Dhubri, the westernmost corner of present-day Assam. Following many battles, Parikshit finally accepted defeat and was sent off to Delhi; but his brother, Bali Narayana took refuge with the Ahoms, who were interested in keeping the Koch as a buffer between themselves and the Mughals. The first Mughal-Ahom battle took place in 1615 when the Mughals attacked the Ahoms, then under Pratap Singha.