Front national de libération du Sud Viêt Nam
Prior to the attack, earlier battles had occurred between the Viet Cong and the village defence militias. On 5 December 1967, two battalions of Viet Cong attacked Dak Son village, and after a battle with the defence militia, killed between 114 to 252 civilians in a "vengeance" attack on the hamlet of Đắk Sơn, home to over 2,000 Montagnards. The Viet Cong believed that the hamlet had at one point given aid to refugees fleeing Viet Cong forces.