- Khmer Rouge ruled from 1975 to 1979
- Leader was Pol Pot who died in 1998
- Charges brought against five top leaders
- "Duch" sentenced to life, two verdicts pending
(CNN)At least 1.7 million people -- nearly a quarter of Cambodia's population -- were killed by execution, disease, starvation and overwork under the Khmer Rouge's brutal rule from 1975 to 1979.