The Purvanchal Range or Eastern Mountains are a sub-mountain range of Himalaya, covering an area of about 94,800 km2 with a population of over four million incorporates Nagaland, Manipur, Tripura and Mizoram Hills and Chachar Districts along with a fifth of Haflong tahsil of Assam State and District of Tripa and part of Lohit in Arunachal Pradesh. Purvanchal as the name itself suggests, it is the eastern frontier region of India being surrounded by Bangladesh in the south-west, Myanmar in the south-east and china in the north-east. Its north-western limit, for a major part, follows the boundaries of Meghalaya and the Mikir hills region, Assam valley, the Eastern Himalaya and the plain areas of Tripura and Cachar are the continuation of the Surma valley.