An attempt by Khmer Rouge leader Pol Pot to form a communist peasant farming society resulted in the deaths of 25 percent of the country's population from starvation, overwork, and executions. Ethnic groups were attacked including the three largest minorities; the Vietnamese, Chinese, and Cham Muslims, along with twenty other smaller groups. Fifty percent of the estimated 425, 000 Chinese living in Cambodia in 1975 perished. Khmer Rouge also forced Muslims to eat pork and shot those who refused. All foreigners were expelled from the country.

Embassies were closed, and any foreign economic or medical assistance was refused. The use of foreign language was banned. Newspapers and television stations were shut down; radios and bicycles were confiscated; and mail and telephone usage was curtailed. Money was forbidden. All businesses were shuttered, religion was banned, education halted, health care eliminated, and parental authority revoked.

Cambodia was sealed off from the rest of the world. On December 25, 1978, Vietnam launched a full-scale invasion of Cambodia seeking to end Khmer Rouge border attacks. On January 7, 1979, Phnom Penh fell and Pol Pot was deposed. The Vietnamese then installed a puppet government consisting of Khmer Rouge defectors. Pol Pot retreated into Thailand with the remnants of his Khmer Rouge army and began a guerrilla war against a succession of Cambodian governments lasting over the next 17 years.

After a series of internal power struggles in the 1990 s, he finally lost control of the Khmer Rouge. In April 1998, 73-year-old Pol Pot died of an apparent heart attack following his arrest, before he could be brought to trial by an international tribunal for the events of 1975-79.