Cambodian Civil War

On 29 March 1970, North Vietnam launched an offensive against the Cambodian army. Documents which were uncovered from the Soviet Union's archives reveal that the invasion was launched at the Khmer Rouge's explicit request after negotiations were held with Nuon Chea. A North Vietnamese force quickly overran large parts of eastern Cambodia reaching within 15 miles (24 km) of Phnom Penh before being pushed back. By June, three months after Sihanouk's removal, they had swept government forces from the entire northeastern third of the country. After defeating those forces, the North Vietnamese turned the newly won territories over to the local insurgents. The Khmer Rouge also established "liberated" areas in the south and the southwestern parts of the country, where they operated independently of the North Vietnamese.

After Sihanouk demonstrated his support for the Khmer Rouge by visiting them in the field, their ranks swelled from 6,000 to 50,000 fighters. Many of the Khmer Rouge's new recruits were apolitical peasants who fought in support of the king, rather than communism, of which they had little understanding.

By 1975, with Lon Nol's government running out of ammunition due to its loss of U.S. support, it was clear that it was only a matter of time before it would collapse. On 17 April 1975, the Khmer Rouge captured Phnom Penh and ended the civil war. Estimates for total civil war deaths vary. Sihanouk used a figure of 600,000 civil war deaths, while Elizabeth Becker reported over a million civil war deaths, military and civilian included; other researchers were unable to corroborate such high estimates. Marek Sliwinski notes that many estimates of the dead are open to question and may have been used for propaganda, suggesting that the true number lies between 240,000 and 310,000. Judith Banister and E. Paige Johnson described 275,000 war deaths as "the highest mortality that we can justify". Patrick Heuveline states that "Subsequent reevaluations of the demographic data situated the death toll for the [civil war] in the order of 300,000 or less".

Arsenal: A place where weapons and other military supplies are stored.

Copperhead: Term for a Northerner who opposed the war effort.

Popular Sovereignty: (pronounced sov-rin-tee) This doctrine was prominent during the debate over slavery in the territories. Popular sovereignty said that the people of each territory should be able to decide for themselves if slavery should be allowed in their territory when it became a state.

Bombproof: A field fortification which was made to absorb the shock of artillery strikes. It was constructed of heavy timbers and its roof was covered with soil.

Works: Fortified structures designed to strengthen a position in battle. This includes earthworks, fieldworks, entrenchments, siege lines, etc.