April 17, 1975 · Phnom Penh, Cambodia Theater

Khmer Rouge fighters enter Phnom Penh after a five-year civil war against the US-backed Lon Nol government. The US Embassy is evacuated by helicopter. Lon Nol's republican forces surrender. Residents pour into the streets to celebrate what they believe is the end of war — only to find that Year Zero has begun.

April 17–20, 1975 · Phnom Penh, Cambodia Theater

Within hours of taking the city, Khmer Rouge cadres order the entire population of 2.5 million at gunpoint onto the roads. Hospital patients are driven from their beds — some still connected to IVs, some mid-surgery. The elderly, the disabled, and the very young who cannot walk are left to die on the road. Thousands perish in the first days from heat, thirst, exhaustion, and execution for moving too slowly. The cadres tell residents it will last only a few days — it will be permanent.

1975–1979 · Phnom Penh, Cambodia Theater

A former high school in Phnom Penh is converted into Security Prison 21 (S-21), run by Kaing Guek Eav, known as 'Duch.' Over four years, an estimated 17,000 prisoners pass through its gates — initially enemy soldiers and Lon Nol officials, then increasingly Khmer Rouge cadres accused of treason, and finally ordinary workers and their entire families. All are subjected to systematic torture to extract confessions and lists of accomplices. Prisoners are photographed on arrival. Bodies are trucked to the Choeung Ek killing fields. Seven people survive.

May 12–15, 1975 · Koh Tang Island, Cambodia Theater

Khmer Rouge naval forces seize the American container ship SS Mayaguez in international waters, taking 39 crew members hostage. President Ford, seeking to project American strength after the fall of Saigon three weeks earlier, orders a military rescue. US Marines assault Koh Tang island in a fierce battle against entrenched Khmer Rouge defenders. 41 Americans are killed — more than the crew being rescued. The crew had already been released by the time the assault began.

1975–1977 · Cambodia-wide Theater

The entire rural population of Cambodia is organized into agricultural cooperatives under Angkar ('The Organization'). Money is abolished. Markets are closed. Religion is banned — Buddhist monks are defrocked, many executed. Schools are shut. Medicine is replaced with folk remedies. Families are separated. Workers receive starvation rations while being forced to work 12-hour days constructing irrigation canals. Those who wore glasses, had soft hands, or spoke foreign languages were marked as 'new people' — class enemies subject to execution.

1977–1978 · Eastern Cambodia Theater

As Pol Pot's paranoia intensified, he turned on his own cadres. The Eastern Zone — whose leaders had fought alongside Vietnamese communists during the independence era — was accused of harboring 'Vietnamese minds in Khmer bodies.' Soldiers from the Southwest Zone were sent to liquidate Eastern Zone cadres, their families, and hundreds of thousands of civilians. Those executed were replaced by loyal Southwest Zone units. The survivors of the Eastern Zone purges fled to Vietnam — and became the nucleus of the Vietnamese-backed liberation force that would invade in 1978.

1977–1978 · Cambodia–Vietnam Border Theater

Convinced that Vietnam was plotting to dominate Indochina, the Khmer Rouge launched a series of cross-border raids into Vietnamese territory, massacring Vietnamese civilians. The worst atrocity was the Ba Chúc massacre of April 1978, where Khmer Rouge soldiers killed more than 3,000 Vietnamese civilians — raping, disemboweling, and decapitating villagers in documented acts of extreme brutality. Vietnam responded with counter-raids and ultimately decided that the Khmer Rouge regime had to be eliminated.

December 25, 1978 · Cambodian border Theater

On Christmas Day 1978, Vietnam launches the largest military operation in Southeast Asia since the end of the Vietnam War. Approximately 150,000 Vietnamese troops, supported by tanks, artillery, and air power, cross the Cambodian border on multiple axes. They are joined by the Kampuchean United Front for National Salvation — Cambodian defectors led by Heng Samrin. The Khmer Rouge army, decimated by internal purges, collapses with shocking speed. Vietnamese forces advance 40 kilometers per day.

January 7, 1979 · Phnom Penh, Cambodia Theater

Vietnamese forces and Cambodian liberation fighters enter Phnom Penh. Pol Pot, Ieng Sary, Nuon Chea, and the Khmer Rouge leadership flee west toward the Thai border, taking gold from the national treasury. The city is found almost entirely empty — a ghost capital. Survivors emerge from the countryside, skeletal and traumatized, searching for family members. The killing stops. The People's Republic of Kampuchea is proclaimed under Vietnamese protection.

1979–1998 · Thai–Cambodian Border Theater

Retreating to the jungles along the Thai border, the Khmer Rouge survive for two decades as a guerrilla force with Chinese weapons and tacit American support — Washington supported the Khmer Rouge's UN seat because Vietnam was Soviet-aligned, a Cold War calculation that prolonged the agony of Cambodia's recovery. The movement fragments through the 1990s. Pol Pot's last years are spent in a jungle compound; he orders the execution of his longtime defense minister Son Sen and family in 1997. In April 1998, facing trial by his own comrades, Pol Pot dies in his sleep. He is cremated before any autopsy can be performed.