In 1969, President Richard Nixon began a secret, illegal, and unconstitutional incursion into Cambodia, correctly believing that Vietnamese communists were using rural parts of the country to transport weapons from North Vietnam to South Vietnam. He ordered carpet-bombing as well as the establishment of military bases in Cambodia. The struggle between American and communist forces quickly destabilized the region, radicalizing many of the already-radical elements in the country.

The most important of the insurgents was a group of existentialist communists, the Khmer Rouge (Red Cambodians), under the leadership of Pol Pot (an assumed name and title) and his organization, The Ankor (The Organization). Pol Pot (1925-1998) was born, Saloth Sar. Though a Roman Catholic and a devout Jeffersonian coming out of high school, Sar attended university in in Paris, from 1949 to 1953, where he came under the influence of several Marxists and, especially, under the influence of the radical, former Nazi-collaborator-turned-communist, philosopher Jean Paul Sartre (1905-1980).
— Read on theimaginativeconservative.org/2016/05/horrors-communism-roland-joffe-the-killing-fields.html