section_path: History/Khmer Republic (1970–1975)
section_name: Khmer Republic (1970–1975)
paragraph_text: Khmer Republic (1970–1975)
  
  While visiting Beijing in 1970 Sihanouk was ousted by a military coup led by Prime Minister General Lon Nol and Prince Sisowath Sirik Matak. Once the coup was completed, the new regime, which demanded that the Vietnamese communists leave Cambodia, gained the political support of the United States. The North Vietnamese and Viet Cong forces, desperate to retain their sanctuaries and supply lines from North Vietnam, launched armed attacks on the new government. The king urged his followers to help in overthrowing this government, hastening the onset of civil war.
  
  Khmer Rouge rebels began using him to gain support. From 1970 until 1972, the Cambodian conflict was largely between the government and army of Cambodia, and the armed forces of North Vietnam. As they gained control of Cambodian territory, the Vietnamese communists imposed a new political infrastructure, which was eventually dominated by the Cambodian communists now referred to as the Khmer Rouge.
  
  Documents uncovered from the Soviet archives after 1991 reveal that the North Vietnamese attempt to overrun Cambodia in 1970 was launched at the explicit request of the Khmer Rouge and negotiated by Pol Pot 's then second in command, Nuon Chea. NVA units overran Cambodian army positions while the Communist Party of Kampuchea (CPK) expanded their attacks on lines of communication. In response to the North Vietnamese invasion, US President Richard Nixon announced that US and South Vietnamese ground forces had entered Cambodia in a campaign aimed at destroying NVA base areas in Cambodia (see Cambodian Incursion).
  
  On New Year's Day 1975, Communist troops launched an offensive which, in 117 days, led to the collapse of the Khmer Republic. Simultaneous attacks around the perimeter of Phnom Penh pinned down Republican forces, while other CPK units overran fire bases controlling the vital lower Mekong resupply route. A US-funded airlift of ammunition and rice ended when Congress refused additional aid for Cambodia. The Lon Nol government in Phnom Penh surrendered on 17 April 1975, 5 days after the US mission evacuated Cambodia.