evacuated to Red Hill. Approximately 200 war wounded were evacuated to Khao-I-Dang. Numerous KPNLAF soldiers and officers, including General Dien Del, reported that during fighting at Nong Samet on 27 December the Vietnamese used a green-coloured "nonlethal but powerful battlefield gas " which stunned its victims and caused nausea and frothing at the mouth. Over 3,500 KPNLAF troops held portions of the camp for about a week after this, but in the end it was abandoned. 31 December: Vietnamese troops ambushed two Thai Ranger units in Buriram Province, wounding six and pinning them down with small arms fire for over 24 hours. 1985 January–February: A powerful Vietnamese offensive overruns virtually all key bases of the Cambodian guerrillas along the frontier, putting the Thais and Vietnamese in direct confrontation along many stretches. 5 January: Paet Um attacked and evacuated. 7–8 January: Five to six thousand Vietnamese troops, backed by artillery and 15 T-54 tanks and 5 APCs, attacked Ampil (Ban Sangae). Vietnamese troops were supported by 400–500 Cambodian KPRAF troops. The attack was preceded by heavy artillery bombardment, with between 7,000 and 20,000 shells falling over a 24-hour period. Nong Chan and Nong Samet were also shelled. Ampil camp fell to the Vietnamese after a few hours of fighting in spite of General Dien Del's predictions. KPNLAF troops disabled 6 or 7 tanks but reportedly lost 103 men in combat. San Ro civilian population evacuated to Site 1. A Thai A-37 Dragonfly ground attack plane, was shot down over Buriram Province during the fighting, killing one of the two crew members. During the assault on Ampil, Thai troops defending Hill 37 near Ban Sangae sustained 11 killed and 19 injured. 23–27 January: Dong Ruk and San Ro camps shelled, 18 civilians were killed. Population of 23,000 fled to Site A. 28–30 January: Vietnamese artillery fired about one hundred 130mm shells, mortars and rockets at positions of the Khmer Rouge's 320th Division near the Khao Din Refugee Camp about 34 miles south of Aranyaprathet. This was followed by an infantry assault on Khao Ta-ngoc. 13 February: Nong Pru, O'Shallac and Taprik (South of Aranyaprathet) attacked and evacuated to Site 8. 16 February: In a skirmish with non-communist rebel forces near Ta Phraya, four Vietnamese rockets containing toxic gas were fired, causing Thai villagers in the area to complain of dizziness and vomiting. A Thai Army laboratory confirmed that the rockets contained phosgene