Between 1975-79, Pol Pot lead Kampuchea through a social engineering experiment. He forced all of his urban residents into the country side to learn farming, in effect forced labor. Doctors, nurses, engineers, musicians, artists...basically anyone with education or training was forced to become a farmer. Those that did not comply were executed. It is estimated that from 2 million to as many as 5 million Cambodians were executed in the name of social engineering, placing Pol Pot on par with Hitler and somewhat below Stalin in the number of his own people killed. But apparently, they were not 'bad people' since it really was the Vietnamese (according to his second in charge).
Al Jazeera English