Susenghphaa (reign 1603–1641), also Pratap Sinha (Singha) was the 17th and one of the most prominent kings of the Ahom kingdom. As he was advanced in years when he became king, he is also called the Burha Raja (Old king). His reign saw an expansion of the Ahom kingdom to the west, the beginning of the Ahom-Mughal conflicts, and a reorganization of the kingdom with an expanded Paik system and reoriented village economy designed by Momai Tamuli Borbarua. His expansion to the west is underlined by the two new offices that he created: that of the Borbarua and the Borphukan. The alliances he formed with the rulers of Koch Hajo resulted in formation that successfully thwarted Mughal expansion. The administrative structure that he created survived till the end of the Ahom kingdom in 1826.
The Mughals entered Kamrup proper. The decisive defeat inflicted by the imperialists on Balinarayan and the Ahoms in November 1637 turned the tide of fortune in favour of imperialists. The whole of Kamrup was cleared and re-annexed to the Pan-Mughalia. The third round of conflict began soon. The imperialists advanced up the Brahmaputra and halted opposite to Samdhara in October 1638; severe fighting ensued. Although the faint-hearted Ahom admiral retired from battle field, the garrison in the fort of Samdhara offered such a gallant defence that the Mughals had to give up the contest with great loss of men and materials.
Treaty of Asurar Ali signed in 1639.The treaty established the boundary between the Mughal empire and the Ahom kingdom ending the Mughal’s efforts to conquer Ahom.
Both sides became eager for peace. Hence a treaty of peace was signed in February 1639. According to the Treaty of Asurar Ali between the Ahom general Momai Tamuli Borbarua, and the Mughal commander Allah Yar Khan, western Assam commencing from Gauhati passed into the hands of Mughals. The Ahom king, for the first time, acknowledged formally the Mughal overlordship in Kamrup, the Mughals acknowledged the independence of the Ahom king and gave up all pretensions to the territories east of Barnadi on the north and Kalang on the south and the Ahom king agreed not to interfere in Kamrup. Besides trade and commercial intercourses were resumed.