In May 1965, two battalions of the 503rd Infantry deployed as part of the 173rd Airborne Brigade to Vietnam as the first major U.S. Army ground combat unit to be deployed, joined later by 4-503rd Inf and 3-503rd Inf (bearing the lineages of the former Company D and Company C, 503rd PIR, respectively). During its six years in Vietnam, the four battalions of the 503rd participated in fourteen campaigns, earning two more Presidential Unit Citations and a Meritorious Unit Commendation. The 2nd Bn (Abn), 503rd Inf participated in the only combat jump of the war during "Operation Junction City" in 1967. It redeployed to the U.S. in July 1971, having the distinction of being one of the last units to leave Vietnam.