Key Facts
- Duration
- 1970–1975 (5 years)
- Founded
- 9 October 1970, following 18 March 1970 coup
- Peak population
- ~7.5 million
- Area
- 181,035 km²
- Collapsed
- 17 April 1975, Khmer Rouge capture of Phnom Penh
Imperial Zenith Metrics
Territorial Scale Comparison
Peak area vs modern sovereign states
Historical Trajectory
Phase I: Rise
The Khmer Republic emerged from a 18 March 1970 coup that ousted Prince Norodom Sihanouk, ending the Kingdom of Cambodia's monarchy. General Lon Nol, backed by the United States, established a far-right militaristic republic formally declared on 9 October 1970. The new government reversed Sihanouk's policy of neutrality, aligning Cambodia with South Vietnam and the US in the Second Indochina War against North Vietnamese and Viet Cong forces operating inside Cambodian territory.
Phase II: Zenith
At its height, the Khmer Republic received substantial US military and financial aid intended to counter both Vietnamese communist forces entrenched in eastern Cambodia and the domestic Khmer Rouge insurgency. The government controlled Phnom Penh and major urban centres, while Lon Nol's administration attempted to centralise authority and modernise the military. However, economic difficulties and the ongoing insurgency severely constrained any stable consolidation of power or meaningful development.
Phase III: Decline
The Khmer National Armed Forces proved poorly trained and unable to withstand the combined pressure of the Khmer Rouge and Vietnamese communist forces. By April 1975, the Khmer Rouge had encircled Phnom Penh; the city fell on 17 April 1975, ending the republic after just five years. The Khmer Rouge briefly restored the name Kingdom of Cambodia before renaming it Democratic Kampuchea on 5 January 1976, ushering in a period of extreme violence.
Notable Imperial Reigns
Selected rulers mapping the empire’s trajectory