Following Cambodian Premier Lon Nol's coup d'état on 18 March 1970, the Khmer Rouge joined Sihanouk's National United Front of Kampuchea (FUNK) in resisting the new government and received military support from both the People's Republic of China (PRC) and the Democratic Republic of Vietnam (DRV, North Vietnam). Although Sihanouk was the nominal head of the National Unity government of Cambodia, he remained in Beijing. Khmer Rouge leader Khieu Samphan exercised real power.
In November 1973 Khmer Rouge forces blockaded Phnom Penh, but at the end of February 1974 Lon Nol's Forces Armées Nationales Khmer (FANK, National Khmer Armed Forces), secretly supplied by the U.S. Central Intelligence Agency (CIA), pushed them back from the capital. In the second half of 1974, however, the less-well-armed but better-led Khmer Rouge came to control the countryside. With only about 70,000 troops, it lacked the strength for an offensive against the cities. The much larger FANK of some 200,000 men controlled the towns but, plagued by poor leadership, low morale, and corruption, was unable to undertake aggressive action in the rural areas. U.S. congressional restrictions of December 1974 on aid to Cambodia adversely affected FANK's fighting ability.
In January 1975 the Khmer Rouge received sufficient North Vietnamese assistance to launch a major offensive against the FANK and soon had cut off land and Mekong River access to Phnom Penh. Lon Nol resigned, and on 17 April Khmer Rouge troops took control of the city. The economy was in ruins. Few schools and hospitals were operating, and half of the population had been uprooted from their homes. But far worse lay ahead. Khmer Rouge leaders renamed the country Kampuchea, emptied the cities, and attempted to take the country back into the Middle Ages, herding the people into agricultural communes and initiating a reign of terror that has few precedents in history.
Under the leadership of Pol Pot, Khieu Samphan, and others, the Khmer Rouge severely restricted access to medical care, education, and religious observances. Intellectuals and the elite were brutally repressed, and thousands of people were separated from their families and denied adequate food. The people were forced to perform hard physical labor in agriculture or in the building of waterways, dams, and other infrastructure. Thousands were tortured and then executed. A Yale University study on Cambodian genocide concluded that as many as 1.7 million of Cambodia's 8 million inhabitants died during 1976–1979 in one of the most horrific genocides in history.
Following border clashes between the Khmer Rouge and Vietnamese troops and atrocities committed against ethnic Vietnamese in Cambodia, on 25 December 1978 Vietnamese forces invaded Cambodia and on 7 January 1979 captured Phnom Penh. The Khmer Rouge then conducted a guerrilla war against the occupiers and the Vietnamese-installed government. Although the Vietnamese occupation ended the wholesale bloodshed in Cambodia, much of the international community, including the United States, condemned it. Only the Soviet bloc recognized the Vietnamese-sponsored People's Republic of Kampuchea (PRK) under Heng Samrin. The United States and the PRC both supported Pol Pot's Democratic Kampuchea.
Vietnamese forces finally departed Cambodia in 1989, and in October 1991 a peace agreement, to which the Khmer Rouge was a party, was signed in Paris. However, the Khmer Rouge boycotted the general election carried out in May 1993 under the provisional government, supervised by the United Nations (UN), and continued its guerrilla activities with the support of Thai generals. In 1994 the new Cambodian government declared the Khmer Rouge illegal and within four years had eliminated major Khmer Rouge strongholds. Most of the senior Khmer Rouge leadership surrendered. The government then resisted international pressure to bring them to trial.
Kosuge Margaret Nobuko and Spencer C. Tucker
Kiernan, Ben. How Pol Pot Came to Power: A History of Communism in Kampuchea, 1930–1975. London: Verso, 1985.; Kiernan, Ben. The Pol Pot Regime: Race, Power, and Genocide in Cambodia under the Khmer Rouge, 1975–79. New Haven, CT: Yale University Press, 1996.