Following World War II, DePuy studied the Russian language, served several tours as an attaché, and was attached to the Central Intelligence Agency (CIA) working in China operations. He went to Vietnam in May 1964 as the chief of operations (J-3) at the Military Assistance Command, Vietnam (MACV). In March 1966, as a major general, he assumed command of the 1st Infantry Division ("The Big Red One"), quickly establishing the division's reputation for agility and rapid response with airmobile assets to overwhelm the Viet Cong. DePuy led the division through the critical battle of Ap Tau O and Operations golden state and attleboro. He earned his second Distinguished Service Cross in Vietnam.
In February 1967 DePuy returned to Washington as the assistant to the vice chief of staff of the army. He was one of the key promoters of the Big Five Weapons Systems—the Apache attack helicopter, the Abrams main battle tank, the Bradley armored fighting vehicle, the Patriot air defense system, and the Blackhawk utility helicopter—that proved so successful in the Persian Gulf and Iraq Wars.
DePuy's greatest influence on the post-Vietnam army came with the establishment of the Training and Doctrine Command (TRADOC) in July 1973 and his appointment to head it as a full general. He forced the army to examine thoroughly and overhaul completely its war-fighting doctrine. The resulting 1976 edition of the capstone manual FM 100–5 Operations reoriented the army from fighting a guerrilla war in Asia to fighting and winning on the continent of Europe against Warsaw Pact forces that were overwhelmingly superior in numbers of equipment and men.
DePuy's concept of active defense was highly controversial and was widely criticized as being too mechanistic and dependent on firepower at the expense of maneuver. Nonetheless, his reforms and the debate that surrounded them generated a renaissance in American military thinking that very shortly led to the recognition of the Operational Level of Warfare and the AirLand Battle doctrine with which both Gulf wars were fought. DePuy retired from the army in July 1977 as a full general. He died in Arlington, Virginia, on 9 September 1992.
David T. Zabecki
Romjue, John L. From Active Defense to AirLand Battle: The Development of Army Doctrine, 1973–1982. Fort Monroe, VA: United States Army Training and Doctrine Command, 1984.