|The Khmer Rouge is blamed for the deaths of at least 1.7 million Cambodians [Reuters]
Below is an overview of the rise and fall of the Khmer Rouge:
1953: King Norodom Sihanouk proclaims independence from France, but soon abdicates to go into politics.
March 1969: Secret U.S. bombing of Vietnamese communist bases in Cambodia begins.
March 18, 1970: US-backed premier Lon Nol ousts Sihanouk as prime minister while the latter is on an overseas trip.
April 17, 1975: Khmer Rouge forces led by Pol Pot capture Phnom Penh. The new government declares the start of Year Zero as it begins a forced relocation to the countryside in their drive to build their vision of an agrarian utopia.
A four-year reign of terror follows that leaves an estimated 1.7 million Cambodians - nearly a quarter of Cambodia's population - dead. Execution, disease, starvation and overwork, were the leading cause of death, according to the Documentation Centre of Cambodia.
December 25, 1978: Vietnam invades Cambodia overthrowing Pol Pot government and installing new regime.
Twelve years of civil war follow pitting the Khmer Rouge, nationalists and royalists against each other.
January 7, 1979: Vietnamese troops occupy Phnom Penh, driving Pol Pot to the Thai border. The occupation is to last 10 years.
May, 1993: National elections produce a shaky coalition between Sihanouk's son, Prince Norodom Ranariddh, and Hun Sen, a former Khmer Rouge guerrilla installed as prime minister by Hanoi in the mid-1980s, following the signing of a UN sponsored peace deal.
1994: The Cambodian government outlaws the Khmer Rouge.
July 25, 1997: Pol Pot is convicted of treason in a show trial organised by disgruntled Khmer Rouge officials.
1998: Anlong Veng, the Khmer Rouge's last stronghold, falls to government forces.
April 15, 1998: Pol Pot dies in a jungle hideout on the run from Cambodian forces.
February 9, 1999: Last Khmer Rouge guerrillas surrender.
March 6, 1999: Ta Mok, the last of the top Khmer Rouge rebels, is arrested and accused of genocide.
May 10, 1999: Cambodian authorities arrest Kaing Guek Eav - better known as "Duch" - for his role as head of the Khmer Rouge S-21 interrogation centre.
2003: United Nations and Cambodian negotiators agree to an international "Killing Fields" tribunal for former Khmer Rouge leaders. The draft agreement is sent to the UN General Assembly and the Cambodian National Assembly for approval before work can go ahead on establishing the court.
April 29, 2005: The UN says legal requirements are met and sufficient funding is in place for the Khmer Rouge trials.
2006: Cambodia's highest judicial body approves 17 Cambodian and 13 international judges and prosecutors for the Khmer Rouge tribunal.
July 21, 2006: Ta Mok, known as "The Butcher", dies before appearing in front of the tribunal.
July 31, 2007: Duch is transferred to custody of the UN tribunal.
September 19, 2007: Top Khmer Rouge leader Nuon Chea, known as "Brother Number Two", is arrested.
November 12, 2007: Former Khmer Rouge social affairs minister Ieng Thirith is arrested along with her husband, former Khmer Rouge leader Ieng Sary.
November 19, 2007: Former Khmer Rouge leader Khieu Samphan is arrested.
November 20, 2007: Pre-trial chamber opens its first public hearing on an appeal by Duch, Khmer Rouge head of the S-21 prison where some 14,000 people died, against his detention.
February 17, 2008: Duch becomes the first former Khmer Rouge official to face trial before the UN tribunal.
July 26, 2010: Duch is found guilty of crimes against humanity and given a 35-year jail sentence, commuted to 19 years.
June 27, 2011: The UN tribunal holds its first hearing in the trials of Nuon Chea, Khieu Samphan, Ieng Sary and Ieng Thirith, accused of genocide, crimes against humanity, religious persecution, torture and other crimes.
February 3, 2011: The UN-backed tribunal sentences Duch to life in prison.