Massacres in the Eastern Zone of Cambodia
In the war leading up the Khmer Rouge takeover, several hundred thousand people died, possibly 100,000 from U.S. bombing. In 1975 to 1979 during the Khmer Rouge period, approximately 1.7 million people died. About a third of those people were deliberately, directly killed, murdered. Possibly two-thirds, or maybe slightly less, were worked to death, starved to death, tortured, or denied medical care or food in ways that make the regime equally responsible for their deaths, although they wouldn't be described as direct murders.
When the Khmer Rouge regime took power in 1975, Pol Pot was at the leadership of the Communist Party of Kampuchea. But, it ran the country through a series of zone branches of that party, and some of the branches were more loyal and more willing to carry out the orders from the Center led by Pol Pot than other branches, or at least the way that's Pol Pot suspected: to some extent correctly, to some extent incorrectly. And so Pol Pot's policy was to slowly, secretly purge his own party and administration of people he considered too moderate or suspect in their loyalty to him and the Party Center.
And the most coherent loyal opposition, if you might call it, was the Eastern Zone branch, which was generally more moderate and had been trained, in many cases, by the Vietnamese communists; it was close to the Vietnamese border. And so Pol Pot saw this particular Communist Party branch as a rival or a threat, and indeed it was headed by the communist official who would most likely have taken over the Party had it not been for Pol Pot succeeding to the Party leadership back in 1962. And so Pol Pot set about undermining the Eastern Zone Party branch quite early, but was unable to do so convincingly and sweepingly, which led to a invasion by the Party Center's army of the Eastern Zone of Cambodia in 1978.
The series of massacres that took place then were the most serious of all the massacres of the Pol Pot regime's genocide. In those four years, the year 1978 was the worst, the largest number of killings. And, of a population of about 1.5 million in the Eastern Zone, probably 250,000 were killed in the last six months of 1978 -- just because of the zone that they lived in, where the Eastern Zone Party branch, having been purged and replaced, had taken to the jungle and started to resist in a conventional rebellion against the Party Center, led by Pol Pot.
And so the Center troops tried to evacuate the entire zone in order to isolate the rebel troops from the population of the zone, killing huge numbers of the people on the spot in large scale mass murders and evacuating others to the west of the country, and then committing genocide against them in large scale mass murders on the spot in the Western Zone of Cambodia and the Northwest, which they hoped would bring the rebellion to the end. In the end, they did succeed in defeating the rebels, who fled across the border into Vietnam with large numbers of supporters and asked for support from the Vietnamese, who then sent their own troops in to overthrow the Pol Pot regime.