 Hagen joined the Army from his birth city of Fargo, North Dakota in 1968, and by August 7, 1971 was serving as a first lieutenant in command of special Recon Team (RT) Kansas, a mixed unit of U.S. Army Special Forces and Montagnard commandos from Task Force One Advisory Element (TF1AE), also known as Command & Control North (CCN) with MACV-SOG (name changed in March 1971 to "TAG" Training Advisory Group, U.S. Army).Hagan's special reconnaissance team had landed and secured their position for the overnight mission almost within sight of the Hanoi High Command's most critical new venture of late 1971, the first six-inch fuel pipeline laid across the Vietnamese DMZ, which was essential a few months in the future when entire tank battalions rolled through the area for the Vietnam War's largest offensive.The North Vietnamese Army (NVA) 304th Division was already massing there, plus a regiment of the 308th Division, in preparation for the 1972 Easter Offensive.