He along with Thuingaleng Muivah and S. S. Khaplang were instrumental in the creation of NSCN on 31 January 1980 after opposing the Shillong Accord signed by the then Naga National Council (NNC) with the Indian government.
[4] Isak Chishi Swu was opposed to the signing of the Shillong Accord by the then Naga National Council (NNC) with the Government of India.
Following a disagreement, he along with Thuingaleng Muivah and SS Khaplang split NNC into a new faction, called the Nationalist Socialist Council of Nagaland (NSCN).
It was later split again when SS Khaplang decided to part ways and created his own faction called NSCN (K) due to clan rivalries among the Konyak people of Nagaland and the Tangkhul Naga of Manipur.
[2] Swu, Muivah and other top NSCN (IM) leaders escaped to Thailand in the early 1990s after a crackdown by the government of India.