FACTBOX: Khmer Rouge casts lingering shadow over Cambodia

(Reuters) - Closing arguments begin next Monday in the trial of chief Khmer Rouge interrogator Duch, the first senior Pol Pot cadre to face a U.N.-backed "Killing Fields" tribunal investigating Cambodia's genocide.

Here are some facts about the Khmer Rouge and how Cambodia is dealing with its legacy:

THE KILLING FIELDS

- Pol Pot's ultra-Maoist Khmer Rouge guerrillas launched a bloody agrarian revolution in 1975, five years after King Norodom Sihanouk was overthrown in a right-wing coup.

- An estimated 1.7 million people -- 21 percent of the population -- were executed or died of disease, starvation or overwork over the next four years in rural labor camps that became known as the "Killing Fields."

THE FALL OF THE KHMER ROUGE

- Vietnamese troops invaded in late 1978 and installed a communist government made up mostly of former Khmer Rouge cadres, including current Prime Minister Hun Sen. Hanoi withdrew in 1989.

- Fighting continued between the government and Khmer Rouge remnants between 1979 and 1991. Millions of Cambodians remained in refugee camps during the unrest.

SLOW ROAD TO JUSTICE

- A 1991 U.N.-brokered peace pact led to elections in 1993 and the restoration of Sihanouk as a constitutional monarch.

- In August 1999, two years after Cambodia asked the United Nations and the international community to help set up a Khmer Rouge genocide tribunal, the government said it wanted to maintain overall control of the court.

- The plan languished for years. Draft laws flew back and forth between Cambodia and the United Nations. The tribunal's legitimacy was questioned in Cambodia and there were calls for world leaders -- from former U.N. leaders to Jimmy Carter, Margaret Thatcher and Henry Kissinger -- to be subpoenaed over their support for Pol Pot's regime.

CRUNCH TIME

- The United Nations gave the go-ahead for a $56.3 million, three-year trial in April 2005, but officials disagreed over the legalities of the Extraordinary Chambers in the Courts of Cambodia, as the joint tribunal is known.

They finally agreed on the basic rules of the court in June 2007, allowing the tribunal to proceed in earnest. Full trials are expected to start next year, but prosecutors say they need more time and cash.

ON TRIAL:

- Five senior Khmer Rouge cadres have been arrested and charged variously with crimes against humanity and war crimes.

They are ex-president Khieu Samphan, former foreign minister Ieng Sary and his wife Khieu Thirith, "Brother Number Two" Nuon Chea, and Duch, who ran Phnom Penh's "S-21" torture and interrogation center.

- Pol Pot, architect of the Khmer Rouge's "Year Zero" peasant revolution, was captured in 1997 and died in April 1998. The one-legged military chief Ta Mok died in 2006.

LIVING LEGACY:

- Thirty years after the regime fell, more than 20,000 ex-Khmer Rouge soldiers and workers live freely in the country.

- Cambodian Prime Minister Hun Sen has blasted the tribunal after acting international co-prosecutor, William Smith of Australia, recommended five more suspects be investigated. Hun Sen said arresting more suspects could spark a civil war.

- While there is no evidence linking him to any atrocities, his government includes many former cadres.

Sources: Reuters, Cambodian Genocide Project ( www.yale.edu/cgp/chron_v3.html )

(Writing by Gill Murdoch; Editing by Martin Petty and Jason Szep)