Chinese scholar Hiuen Tsang (c. 640 AD) records the existence of the town Pehowa, named after Prithu, "who is said to be the first person that obtained the title Raja (king)".
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The town is referred as the boundary between Northern and central India and referred to by Patanjali as the modern Pehowa.
This was followed by the defeat of Giasuddin in 1227, but in 1228, Prithu was defeated by Mahmud Shah, the son of Iltutmish, and the Turkic army reached the Nagaon area.
In 1228, Nasiruddin attacked and killed Prithu, a Khen ruler (reigned: 1185–1228) of Assam.