The Cambodian Civil War was a military conflict that pitted the guerrilla forces of the Maoist-oriented Communist Party of Kampuchea (nicknamed the Khmer Rouge) and the armed and security forces of the Nonaligned Kingdom of Cambodia from 1967 to 1970, then between the joint Monarchist, Maoist and Marxist-Leninist National United Front of Kampuchea alliance and the pro-western Khmer Republic from 1970 to 1975. Main combatants comprised:
- The Khmer National Armed Forces (French: Forces Armées Nationales Khmères), best known by its French acronym FANK, were the official armed defense forces of the Khmer Republic from 1970 to 1975. Subordinated to the Ministry of Defense of the Cambodian Republican Government at the national capital Phnom Penh, the FANK branches were organized as follows:
- Khmer National Army (French: Armée Nationale Khmère – ANK)
- Khmer Air Force (French: Armèe de l'Air Khmère – AAK)
- Khmer National Navy (French: Marine Nationale Khmère – MNK)
- Paramilitary security forces:
- Khmer National Police (French: Police Nationale Khmère – PNK)
- Khmer National Gendarmerie (French: Gendarmerie Nationale Khmère – GNK)
- The Cambodian People's National Liberation Armed Forces (CPNLAF) were the official armed wing of the National United Front of Kampuchea (French: Front uni national du Kampuchéa or Front uni national khmer – FUNK), an umbrella organization dedicated to the armed overthrow of the pro-western Khmer Republic. Technically subordinated to the exiled Royal Government of the National Union of Kampuchea (French: Gouvernement royal d'union nationale du Kampuchéa – GRUNK) based in Beijing, the CPNLAF comprised the following three guerrilla movements:
- The Khmer Rumdo, also spelt Khmer Rumdos or Khmer Rumdoh ("Liberation Khmer" in the Khmer language), a pro-Sihanoukist (monarchist) faction founded in 1970;
- The Khmer Issarak ("Free Khmer" or "Independent Khmer" in the Khmer language), a pro-Soviet Marxist-Leninist faction closely aligned with both the monarchist Khmer Romdo and North Vietnam;
- The Khmer Rouge, a collective designation coined to the Maoist-oriented Communist Party of Kampuchea (CPK) and its military wing, the Revolutionary Army of Kampuchea (RAK), active in Cambodia since 1967, which were aligned with the People's Republic of China.
- The Khmer Serei ("Free Khmer" in the Khmer language), a far-right, anti-communist and anti-monarchist guerrilla group active in Cambodia between 1955 and 1969, which was secretly backed by the United States and South Vietnam, being subsequently absorbed into the FANK in 1970.
- The Army of the Republic of Vietnam (ARVN), which received support from the United States, Australia, Canada, France, West Germany, Israel, Japan, New Zealand, Philippines, South Korea, Francoist Spain, Taiwan, Thailand and the United Kingdom.
- The People's Army of Vietnam (PAVN), also designated the "North Vietnamese Army" (NVA), which received support from the Soviet Union, the People's Republic of China, North Korea, East Germany, Czechoslovakia, Poland, Hungary, Bulgaria and Yugoslavia.