A member of the post-war provisional government (1945–46), he opposed French recolonization and was elected Premier in 1951. During his first premiership (1951–54) civil war broke out between the government and the communist-led Pathet Lao movement. He formed a brief coalition (1962–63) with the Pathet Lao (led by his half-brother, Prince Souphanouvong) and after the return of civil war, he continued as Premier. Although he tried to maintain a neutral policy during the Vietnam war, this proved impossible. In 1973 he signed a ceasefire agreement with the Pathet Lao and remained Premier until the People’s Democratic Republic of Laos was declared in 1975.