Lance Corporal Lumbard was serving as Vehicle Commander of an amphibian tractor supporting a Marine infantry company during a search and clear operation in known enemy infested terrain when the lead element of the company came under extremely heavy small-arms and recoilless rifle fire in the vicinity north of An Hoa. One of the supporting tractors sustained severe hits and was disabled.

Reacting immediately, Lance Corporal Lumbard maneuvered his vehicle alongside and, braving the withering fire, cimbed aboard in a gallant attempt to aid his comrades.

Finding the crew had been killed, he exhibited exceptional presence of mind in unloading the stricken vehicle's mortars and ammunition and distributing them to other units engaged in the vicious action. Undaunted by the increasingly heavy fire, he returned to the disabled vehicle and manned its machine gun, directing a devastating volume of fire at enemy positions until the ammunition was exhausted. He then raced to another damaged vehicle and used its machine gun to battle the Viet Cong.

Then, turning the machine gun over to another Marine, he valiantly exposed himself to the hail of fire to distribute water, assist in the evacuation of the wounded and deliver supplies to units who were in dire need. Observing an unmanned machine gun, he was attempting to put it in action when he was painfully wounded by fragments from a recoillesss rifle round. Ignoring his pain, he administered first aid to two comrades wounded at the same time. Helping them aboard an amphibian tractor, he assisted the crew chief to maneuver the vehicle to a defilade position. When the vehicle carrying the wounded was hit, he reported the situation to the senior noncommissioned. officer before being evacuated.