On December 5, 1967, two battalions of Viet Cong systematically killed 252 civilians in a "vengeance" attack on the hamlet of Đắk Sơn, home to over 2,000 Montagnards, known for their fierce opposition to the Viet Cong. The Vietcong believed that the hamlet had at one point given aid to refugees fleeing Viet Cong forces.
Over 600 troops marched into the village, using flamethrowers to destroy the shelters and kill the men, women, and children who lived there. As the Viet Cong fired their weapons, people were incinerated inside their own homes, and some who had managed to escape into foxholes in their homes died of smoke inhalation. The homes that were not destroyed by flamethrowers were destroyed with grenades, and on the way out patches of the main town were set afire. Just before they left the village, the Viet Cong shot 60 of the 160 survivors. Most of the remaining villagers were taken hostage.