Who were the Khmer Rouge? In 60 secs
7 August 2014 Last updated at 17:49 BST
Two top Khmer Rouge leaders have been jailed for life after being convicted by Cambodia's UN-backed tribunal of crimes against humanity.
Nuon Chea served as Pol Pot's deputy and Khieu Samphan was the Maoist regime's head of state.
They are the first top-level leaders to be held accountable for its crimes.
Up to two million people are believed to have died under the Khmer Rouge regime.
BBC News explains who the group were and what they stood for - in 60 seconds.
Video produced by Michael Hirst