Vietnamese troops seize the Cambodian capital of Phnom Penh, forcing Pol Pot and his communist Khmer Rouge forces to retreat into the jungle. In the early 1970s, North Vietnam supported the Khmer Rouge in its guerrilla war against the U.S.-backed Cambodian government, but as the Vietnam War came to an end, relations deteriorated between Pol Pot and communist Vietnam.
In April 1975, Pol Pot captured Phnom Penh, and two weeks later Saigon fell to the North Vietnamese. Efforts by Vietnam to expand its influence in Indochina were opposed by Pol Pot's regime, and border skirmishes between Vietnam and Cambodia escalated into full-scale combat by 1978. Meanwhile, Pol Pot's brutal agrarian revolution resulted in the deaths of as many as 2 million Cambodians. After three years of terror, Vietnamese forces invaded in December 1978, and in January installed a puppet regime let by moderate Cambodian communists. Pol Pot continued to rule over the banished Khmer Rouge for two more decades. He died of apparently natural causes in 1998.