(TIME) The Rise and Fall of the Khmer Rouge

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Royal Seal of Approval
In 1965, Prince Norodom Sihanouk, Cambodia's head of state, asserted the nation's opposition to the U.S.-backed government in South Vietnam by allowing North Vietnamese guerrillas to set up bases within Cambodia's borders. The North Vietnamese had an alliance with a Cambodian Marxist insurgency group, the Khmer Rouge, whose top brass Sihanouk is pictured here with in 1973.

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Losing Control
A Cambodian soldier holds a .45 to the head of a Khmer Rouge suspect in 1973. When Sihanouk was forced out of power in a coup, the new Prime Minister, General Lon Nol, sent the army to fight the North Vietnamese and the Khmer Rouge in Cambodia. Fighting two enemies proved to be too much for Cambodia's army. As Civil War raged from 1970 to 1975, the army gradually lost territory as Khmer Rouge increased its control in the countryside.

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Coming Apocalypse
Survivors sift through rubble after the Khmer Rouge bombed Phnom Penh, the capital city, on January 1, 1975. Four months later, the party took the city, on April 17, 1975, and began their mission of returning Cambodia to an agrarian society, emptying the cities and forcing their countrymen into agricultural labor.

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Day One, Year Zero
Khmer Rouge fighters celebrate as they enter Phnom Penh on April 17, 1975. Prince Sihanouk, the party's early ally, resigned in 1976, paving the way for the now notorious Khmer Rouge founder and leader, Pol Pot, to become prime minister. The country was renamed Kampuchea, and it was the start Year Zero — the beginning of a new history for Cambodia written by Pol Pot.

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Left Behind
Days before the occupation of the capital, thousands of Cambodians gather behind a school perimeter fence near the American embassy to watch the final evacuation of U.S. and foreign nationals.

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Death Sentence
A prisoner gets her mug shot taken. At prisons like Phnom Penh's infamous Tuol Sleng, prisoners were painstakingly documented before being sent to their deaths in mass graves later to be come known as the "killing fields." Hundreds of thousands of intellectuals were tortured and executed under the Khmer Rouge; others starved or died from disease or exhaustion. In total, an estimated 1.7 million Cambodians died between 1975 and 1979.

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Pol Pot's Utopia
An undated photograph shows forced laborers digging canals in Kampong Cham province, part of the massive agrarian infrastructure the Khmer Rouge planned for the country.

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A New Occupier
Fed up with cross-border raids by Khmer Rouge, Vietnam invaded Cambodia on Dec. 25, 1978. By Jan. 7, shown here, Vietnamese troops had occupied Phnom Penh. The Vietnamese occupation of Cambodia lasted for 10 years.

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Fearless Leader
The Vietnamese overthrew Pol Pot, too, driving the leader to the Thai border where he continued to head the Khmer Rouge in the jungles.

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Purging the Western Curse
The Khmer Rouge sought to rid Cambodia of all Western influences that distracted its people from their agrarian calling. Cars, abandoned and forbidden, were stacked up alongside the road.

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A Bloody Landscape
An exhumed mass grave, pictured in 1981, in the Cambodian countryside reveals the skeletons of those executed and buried together under Pol Pot's regime.

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The Resistance
Khmer Rouge guerrillas in the jungle of western Cambodia as they attempt to halt advancing Vietnamese forces on Feb. 15, 1981.

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Running for Cover
Cambodian refugees, pictured in January 1985, at a refugee camp, near the Thai-Cambodian Border. Some 60,000 people fled to the south as fighting increased between Khmer-Vietnamese troops and the FNLPK (Khmer People's National Liberation Front), one of the three groups making up the anti-communist resistance.

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Out from Under the Iron Curtain
Without backing from the Soviet Union, Vietnam could no longer afford to keep its troops in a state of indefinite occupation in Cambodia. In September 1989, Vietnamese troops withdrew from Phnom Penh.

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A Tearful Reunion
A family greets each other in August 1989 after being separated during years of war and occupation.

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Return the Old Guard
The 1991 Paris Peace Accord that followed Vietnam's withdrawal mandated democratic elections and a ceasefire, but was not fully respected by Khmer Rouge guerrillas. U.N. transitional authority shared power with representatives of various factions, and Prince Sihanouk, shown here at center making his way back the Royal Palace in November 1991, was reinstated as Head of State.

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Forgiven
U.N.-run elections in May 1993 resulted in a shaky coalition between Sihanouk's son, Prince Norodom Ranariddh, and Hun Sen, a former Khmer Rouge guerrilla pictured here at a political rally before the elections. The country was once again named the Kingdom of Cambodia. Hun Sen remains Prime Minister today.

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The Banality of Evil
Pol Pot continued to lead the Khmer Rouge party from rural Cambodia until July 1997 when he was arrested. In a show trial, Pol Pot, known as Brother No. 1, was denounced by his own followers and sentenced to house arrest in his jungle home. The press gathered there when he died less than a year later at age 73 on April 15, 1998, never having faced charges.

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A New Chapter
Finally agreeing to abandon their fight, the remaining Khmer Rouge soldiers fighters surrendered on Feb. 9, 1999, and donned new uniforms of the Royal Cambodian Armed Forces during an integration ceremony in Anlong Veng near the Thai-Cambodian border.

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Documenting the Aftermath
Contact sheets showing pictures of what is believed to be former prisoners of the S-21 prison, also known as Tuol Sleng, where over 15,000 people lost their lives. Kaing Guek Eav, better known as Duch, was detained for his role as chief of the torture center in 1999.

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The World Watches, and Waits, for Justice
A long delayed U.N.-backed tribunal to bring the leaders of the genocide to justice began in 2009. On Feb. 17, Duch's trial began. He is the first of five defendants scheduled for trial.