Burma National Army
During the Japanese occupation of Burma, Kyaw Nyein was Cabinet Secretary in the "Civil Executive Administration" under Prime Minister Dr. Ba Maw, and later served as Vice Minister of Foreign Affairs. In August 1944, he participated in negotiations between members of the Communist Party of Burma, the PRP and the Burma National Army that led to the founding of the anti-Japanese resistance organization, Anti-Fascist Organisation (AFO), which later became the Anti-Fascist People's Freedom League (AFPFL). Kyaw Nyein was a member of the AFO Supreme Council, the Military Council, and the executive committee and assigned as Political Commissar to Division (6), Pyinmana.