He transferred to South Vietnam in July 1967, where he served successively as Commanding Officer, Service Company, Headquarters Battalion, and Commanding Officer, Company H, 2nd Battalion, 5th Marines, 1st Marine Division, FMF. During the Battle for Hue City in 1968, Christmas was seriously wounded and evacuated to the Philadelphia Naval Hospital. For his actions of "extraordinary heroism" in Hue City on February 5, 1968, he was awarded the Navy Cross.