MacDonald enlisted in the United States Army on June 28, 1969, and was sent to Fort Sam Houston, Texas to undergo a six-week physician's basic training course. While at Fort Sam Houston, he volunteered to be assigned to the Army's Special Forces ("Green Berets") to become a Special Forces physician. He was then assigned to Fort Benning, Georgia, where he completed their paratrooper training course. Although MacDonald had joined the Army knowing he might be deployed to serve in the Vietnam War, he later learned that, as a Green Beret doctor, he was unlikely to serve overseas. Fort Bragg In late August, MacDonald reported to the 3rd Special Forces Group (Airborne) at Fort Bragg, North Carolina to serve as the group's surgeon. He was joined by his wife and children, and the MacDonald family resided at 544 Castle Drive, in a section of the base reserved for married officers and afforded security by military police. The couple quickly became popular among their neighbors, although MacDonald and Colette are known to have argued occasionally. By the time the MacDonalds moved into their new apartment at Fort Bragg, Colette had accrued two years of studies, with aspirations to obtain a bachelor's degree in English literature and teach part-time. Both daughters had developed distinctive personalities: Kimberley being markedly feminine, intelligent, and shy; Kristen a boisterous tomboy who would "run over and crack someone" if she observed her older sister being bullied by other children. On December 10, the 3rd Special Forces Group was deactivated, and MacDonald was transferred on base to Headquarters and Headquarters Company, 6th Special Forces Group (Airborne), 1st Special Forces, to serve as a preventive medical officer. Shortly before Christmas 1969, with his wife approximately three months pregnant with their third child and first son, MacDonald bought his daughters a Shetland pony, anticipating the family would soon relocate to a farm in Connecticut. He kept this purchase a secret from his wife and children, and he and his stepfather-in-law drove them to the stable as a surprise on Christmas Day. His daughters chose to name the pony "Trooper". The same month, Colette is known to have penned a letter to college acquaintances in which she described her life as "never [being] so normal or happy", adding she and her husband were content, that their baby son was due to be born in July, and her family would be complete. By