In the north of the Indian sub-continent lie the formidable Himalayas. Geographically these can be divided into three broad regions, namely:

• The Eastern Himalayas• The Central Himalayas, and• The Western Himalayas

The eastern branch of the Himalayas, the Patkai hills with its extension in the form of the Khasi, Garo and the Jaintia hills, closes the Brahmaputra valley from the south, adding to the isolation of Assam. South of Manipur, the Lushai and the Chin hills narrow into a long range of hills of the Arakan Yoma range, which demarcate the border with Myanmar and take it to Cape Negaris situated on the mouth the Irrawaddy river.

Although the routes through the eastern mountains are difficult, that has not prevented the flow of cultural influence from Southeast Asia and South China. The region has also witnessed a few military invasions from the east as also the gradual and partly peaceful penetration by people like the Ahoms, from Arakan into the Assam valley.