A camp had been established in a critical position to the SW of Hue, about 2 miles from the border with Laos. There were at least 3 covert Viet Cong (VC) supply trails nearby, leading through the mountains and into South Vietnam. The camp was garrisoned with a small number of US Special Forces, and c 250 South Vietnamese Army (ARVN) and others.
VC activity had been increasing since mid Feb as preparations with anti-aircraft guns and artillery pieces were being moved into place, for a full-on assault on the camp. In poor weather during the night of 8 Mar that assault began. It ratcheted up in intensity in the following days. Air support from USAF A-1E and AC-47 and US Army O-1 was hampered by the low cloud base and intense enemy fire but several Medevacs were attempted. With the defenders becoming short of food, water and ammunition, tired and with many wounded, a decision was taken in the late afternoon of 10 Mar, despite the poor weather and very difficult flying conditions, that the base would be evacuated by helicopter.
16x UH-34 of HMM-163 departed
Phu Bai, supported by 6x UH-1E from VMO-2 and various fixed wing strike aircraft from other USMC and USAF units. On the following day, further rescue missions were flown. By early afternoon on 11 Mar, those that could be evacuated had been. 21 of the 24 UH-34 on HMM-163s strength had to be replaced, either after being shot down or damaged by enemy fire. The VC overran the base shortly afterwards.
HMH-363 US Marine Corps 