[1] Chan Sy was a Cambodian of Chinese descent[2] who early in his life became a military figure[3] by joining the Khmer Viet Minh forces in 1950s.

A member of the Communist Party from 1960, Chan Sy was believed to have returned to Cambodia in 1970 after the coup that ousted Prince Sihanouk and placed the pro-U.S. Lon Nol in power.

Considered a steadfast adherent to Vietnam's Kampuchean policy, Chan Sy had made visits to Bulgaria, East Germany as well as to the Soviet Union.

[3] Chan Sy spent many years in Vietnam and was a founding member of the Kampuchean United Front for National Salvation (FUNSK) that overthrew Pol Pot's regime.

After the establishment of the People's Republic of Kampuchea, he became chief political commissar of the armed forces,[4] and eventually appointed by the National Assembly as Prime Minister on February 9, 1982.