The most notorious of the 189 known interrogation centers in Cambodia was S-21, housed in a former school and now called Tuol Sleng for the hill on which it stands. Between 14,000 and 17,000 prisoners were detained there, often in primitive brick cells built in former classrooms. Only 12 prisoners are believed to have survived.
S-21 confined mostly “elite” prisoners from the Khmer Rouge’s own ranks. Their jailers kept meticulous records, taking black-and-white mug shots of prisoners on entry, and used electric shocks, beatings, and water poured in the nose to extract elaborate written confessions to real and imagined offenses. Being in the pay of the CIA or the Vietnamese or a purged Khmer Rouge figure were commonly forced confessions.
Some prisoners died at S-21 from their mistreatment, but most others were executed at a nearby killing center known as Cheoung Ek. Deaths were sometimes recorded with photos of corpses.
Suspicion and distrust within the Khmer Rouge ranks mounted, spurred in part by the failure to meet the unattainable goals for rice production dictated by the Four-Year Plan. Failing to perform one’s duty for Angkar was treason.
Paranoia about hidden agents for Vietnam, Thailand, and the CIA also fed the frenzy of roundups. In Khmer Rouge justice, it was not enough to “smash” one suspect figure—that person’s subordinates and family had to be eliminated too. In this way, thousands of Khmer Rouge cadres and the people around them were imprisoned, interrogated, tortured, and executed. Significant numbers of one-time Khmer Rouge loyalists, fearing for their lives, defected across the border to Vietnam. But ultimately it was not the Khmer Rouge’s violence against fellow Cambodians that brought the regime down. It was war against neighbors. In 1977, the Khmer Rouge began launching armed incursions into Vietnam, Thailand, and Laos. Often the goal was to regain territories that had been ruled by the Khmer Empire centuries earlier.
In late December 1978, Vietnam launched a full-fledged invasion of Cambodia, sending tanks and thousands of ground troops across the frontier. Khmer Rouge fighters fell back in disorder.
On January 7, 1979, Vietnamese forces entered a largely deserted Phnom Penh. The Khmer Rouge era was over.