John Dunn was born in Hutchinson, Kansas in 1943. He enlisted in the U.S. Army on February 8, 1966, and completed Basic Training and Advanced Infantry Training at Fort Jackson, South Carolina, before receiving a commission as a 2LT through Infantry Officer Candidate School on December 16, 1966. He then completed Military Intelligence Officer School at Fort Hollabird, Maryland, and served with the 113th Military Intelligence Group at Fort Sheridan, Illinois, from May to October 1967. In November 1967, Dunn was sent to Southeast Asia and was stationed in the Republic of Vietnam, where he served with Military Assistance Command Vietnam Team 38 as an Intelligence Officer. He was wounded by a rocket-propelled grenade and then again by a hand grenade, captured, and taken as a Prisoner of War by the Viet Cong in South Vietnam on March 18, 1968. After spending 1,792 days in captivity in South Vietnam and Cambodia, he was released during Operation Homecoming on February 12, 1973. After his return, Dunn completed the Military Intelligence Officers Advance Course at Fort Huachuca, Arizona, and then served in the Counter Intelligence Analysis Detachment in Washington, D.C., from June 1974 to June 1975. He then served as an Intelligence Watch Officer in the Army Operations Center at the Pentagon from June 1975 to May 1978, followed by a tour with the Domestic Contact Division with the Central Intelligence Agency in San Francisco, California, from June 1978 to August 1982. Col Dunn then served as a Detachment Commander and Staff Officer with the Intelligence Support Activity in Washington, D.C., from August 1982 to June 1985. His final assignment was as Base Commander of Operational Base Munich, of the 430th Military Intelligence Battalion, located in West Germany, where he served from June 1985 until his retirement from the Army on November 1, 1988.

His Silver Star Citation reads:

Captain John G. Dunn, Military Intelligence, is awarded the Silver Star for heroism involving voluntary risk of life while serving as a Prisoner of War during May 1968. Ignoring international agreements on treatment of prisoners of war, the Viet Cong resorted to a routine of mental and physical cruelties including withholding of medical treatment and food, for the purpose of obtaining military information, biographical data, and propaganda material detrimental to the United States. During the latter part of May 1968, Captain Dunn was undergoing intense interrogation for the purpose of obtaining military information. Even though he was forced to live in a filthy pit, chained by the ankle like an animal, given only enough to eat to sustain life, severely beaten, and his life threatened, Captain Dunn would not give the requested information. After being refused food and water for three days, he still refused to give information. At midnight on the third day he was tied, blindfolded, taken to the jungle, placed on his knees and an AK-47 rifle placed to his head and told that he had 60 seconds in which to give them the desired information. At this time, he agreed to their demands, but gave them false and distorted information, hoping for enough time to regroup his thoughts. Instead, he was again given ten minutes to live and, again, he refused to give additional information. Shortly after this last threat, he was returned to his bunker and camp routine was restored. Despite extremely harsh conditions, he never wavered in his devotion and loyalty to God, country, and fellow prisoners. The heroism displayed by Captain Dunn reflects great credit upon himself, his family, and the United States Army.