During the Vietnam War, he was in charge of the largest Forward Air Control Base at Long Tiên, ultimately completing three tours in the war- torn country. As a pilot with the 559th TFS (Tactical Fighter Squadron), part of the 12th Fighter Wing (Billy Goats), he flew more than 800 hours of combat missions from Cam Ranh Bay providing close air support, and also flying between 750-1000 combat hours hitting targets along the protected Ho Chi Minh trail in Laos. His list of proficiency with aircraft included, but was not limited to: A-1 (A,D6), F-4 (B,C,J), O1 (E,F), U-17, T28B, T33, T-34A, T39, F86F, F5E, RF5A, F5B, F100 (C,D,F).
But most important to him, it was in Cam Ranh Bay in 1969 that he met his second wife Jean Anne Youngstrom, a combat nurse in Vietnam, and the love of his life.
While serving in Vietnam, Mark was soon attached to the CIA to support the Lao Hmong guerrilla army with a number of other exceptional pilots known as the Ravens. Most of those missions were declassified in the late 1980s and these warriors, unlike any today, are immortalized in two books, The Laotian Fragments and The Ravens: Pilots of the Secret War in Laos, cementing their legacy as a true heroes.
Later in 1974, he was assigned the role of Military Attaché to the Shah of Iran, where he trained the Persian Air Force and introduced electricity to remote mountain villages in the region.
Back in Texas, when asked what medals he earned in combat, he often said, “Every time they nominated me for a medal, I told them to give it to that guy or this guy, there are plenty of men who flew more hours and deserved it more than I did.” Nevertheless, among his many medals earned in combat, he was awarded not one but two Distinguished Flying Crosses (the highest medal for extraordinary aerial achievement), and he was the first ever member of the U.S. Air Force to receive a Navy Commendation Medal. He loved flying with the U.S. Marines!
Away from the cockpit, Col. Diebolt had a passion for politics, authors such as Lawrence Durrell, the French language, the timeless melodies