<Table> <Tr> <Th_colspan="2"> Khmer Rouge </Th> </Tr> <Tr> <Td_colspan="2"> ខ្មែរ ក្រហម </Td> </Tr> <Tr> <Td_colspan="2"> The flag of Democratic Kampuchea . The design was used by Khmer guerrillas since the 1950s with the building design varying . </Td> </Tr> <Tr> <Th> Active </Th> <Td> 1951--1999 </Td> </Tr> <Tr> <Th> Ideology </Th> <Td> Agrarian socialism Khmer nationalism </Td> </Tr> <Tr> <Th> Leader </Th> <Td> Pol Pot </Td> </Tr> <Tr> <Th> Headquarters </Th> <Td> Phnom Penh </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Khmer Rouge </Th> </Tr>

When did the khmer rouge start and end