( 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 . Three of the ultra-Maoist regime 's former leaders have been found guilty for crimes against community by a U.N.-backed tribunal . On Thursday , guilty verdicts were handed down to Nuon Chea , otherwise known as Brother Number Two , and Khieu Samphan , the one-time President of Democratic Kampuchea , as Cambodia was known . Kaing Guek Eav , alias Comrade Duch , the head of an infamous torture prison , was convicted of crimes against humanity in 2010 . He was ultimately sentenced to life in prison in 2012 , more than 30 years after the fall of the regime . Here 's a timeline of the Khmer Rouge regime and the long path to bring its leaders to justice : . 1970 : Marshal Lon Nol stages a coup , forcing Prince Norodom Sihanouk out of power . Sihanouk is aligned with the Khmer Rouge , an ultra-Maoist group building up a following in the countryside . April 17 , 1975 : The Khmer Rouge seize Phnom Penh , completing their taking over of the country . The city 's inhabitants are forced to leave the capital , heading out to rural areas . Some two million people are forced out of Cambodia 's urban centers . Late 1977 : Fighting breaks out between Vietnam and Cambodia . May 25 , 1978 : Khmer Rouge purges East Zone . January 7 , 1979 : The Vietnamese take Phnom Penh , beginning 11 years of Vietnamese occupation . The Khmer Rouge move west . Some Cambodians celebrate January 7 as a liberation day from the Khmer Rouge , while others mark it as the start of Vietnamese occupation . 1979 : A genocide tribunal in Phnom Penh finds Pol Pot and Ieng Sary guilty of genocide . Neither appeared in court or served any sentence . 1982 : Triparty coalition government forms , consisting of Prince Sihanouk , who was exile in China , the Khmer Rouge and non-communist leader Son Sann to create the Triparty Coalition Government . Vietnam helps establish a new government led by Heng Samrin . 1990 : Vietnamese troops withdraw from Cambodia . October 23 , 1991 : Paris peace talks . A peace accord among all Cambodian parties is signed . They approve holding a national election under the supervision of the United Nations Transitional Authority in Cambodia . The Khmer Rouge boycott the polls and wo n't demobilize their forces . May 23-28 , 1993 : The U.N.-supervised elections are held . A royalist party lead by one of the king 's sons , Ranariddh , wins a plurality and forms a coalition government with the Cambodian People 's Party . Ranariddh and Hun Sen of the CPP are appointed co-prime minister . Khmer Rouge soldiers continue to wage guerrilla war . 1996 : King Norodom Sihanouk pardons top cadre Ieng Sary 's genocide sentence from the 1979 genocide tribunal . 1997 : The Khmer Rouge tries Pol Pot for crimes allegedly committed within the regime after 1979 . Cambodia asks the U.N. to help create a court to prosecute the surviving top leaders of the Khmer Rouge . 1998 : Pol Pot dies . Civil war ends in Cambodia . 1999 : Considered the end of the Khmer Rouge . 2001 : Cambodia 's National Assembly passes a law to create a court to try serious crimes committed during the Khmer Rouge regime . 2003 : Agreement is reached with the U.N. on how the international community would help and participate in the Extraordinary Chambers in the Courts of Cambodia . The pact was amended in 2004 . June 2007 : The court becomes fully operational . November 20 , 2007 : The pre-trial chamber opens its first public hearing on an appeal by Duch , the Khmer Rouge head of the S-21 prison , where some 14,000 people died . July 26 , 2010 : Duch is found guilty for war crimes , crimes against humanity , murder and torture , and sentenced to 35 years in prison . February 3 , 2012 : Duch 's sentence extended to life in prison . August 7 , 2014 : Nuon Chea , otherwise known as Brother Number Two , and Khieu Samphan , the one-time President of Democratic Kampuchea , are found guilty and sentenced to life in prison . Sources : Cambodia Tribunal Monitor ( David Scheffer , Khamboly Dy ) , Extraordinary Chambers in the Courts of Cambodia , United Nations .
Khmer Rouge ruled from 1975 to 1979 . Leader was Pol Pot who died in 1998 . Charges brought against five top leaders . Comment: