
The Cambodian Civil War ends in 1975, with Phnom Pneh falling to the Khmer Rouge, beginning a reign of terror that turned the country into the killing fields, and would lead to the death of close to 2 million in one of the worst ever genocides post WW2.
The Khmer Rouge was heavily backed by China, and they were finally overthrown by the Vietnam Army in 1979, bringing an end to a reign of terror, that devastated Cambodia and pushed it back by a decade or so.
Ironically it was the King of Cambodia Norodom Sihanouk, who was responsible for the Khmer Rouge's growth, when he allied with them after he was overthrown in a coup. It would soon turn out to be a Frankenstein that went beyond control, backed by China.