Pol Pot was a political leader whose communist Khmer Rouge government led Cambodia from 1975 to 1979. During that time, an estimated 1.5 to 2 million Cambodians died of starvation, execution, disease or overwork. One detention center, S-21, was so notorious that only seven of the roughly 20,000 people imprisoned there are known to have survived. The Khmer Rouge, in their attempt to socially engineer a classless communist society, took particular aim at intellectuals, city residents, ethnic Vietnamese, civil servants and religious leaders. Some historians regard the Pol Pot regime as one of the most barbaric and murderous in recent history.