From April 17, 1975 to January 7, 1979, the Khmer Rouge was responsible for killing almost two million Cambodians. The communist regime of the Khmer Rouge aimed to change the country into a classless society based on agrarianism. Within the first week, over two million people were evacuated from the citites and moved to the countryside where they would be used in forced labor. Almost 20,000 of these people would be sent to the Tuo Sleng Centre, a prison more commonly known as S-21. Those who opposed the regime were either sent to a prison or were sent to the Killing Fields where they would be killed then disposed of in mass graves. The genocide and the reign of the Khmer Rouge was ended by the invasion of the Vietnamese in 1979. In the early 2000s, the Khmer Rouge Tribunal was established to try leaders of the Khmer Rouge for genocide and crimes against humanity. Only five people have been indicted for these crimes.