On August 5, 1950, 5th Marines were deployed to the Pusan Perimeter as part of the Provisional Marine Brigade. From there, they participated in the Inchon Landing, Battle of Chosin Reservoir and fighting on the East-Central Front and Western Front until the end of hostilities. Immediately after the war, they participated in the defense of the Korean Demilitarized Zone from July 1953 until February 1955. The regiment returned to Camp Pendleton in March 1955.