Bolton was a supporter of the Vietnam War, but purposely avoided military service in Vietnam. During the 1969 Vietnam War draft lottery, Bolton drew number 185. (Draft numbers were assigned by birth date. ) As a result of the Johnson and Nixon administrations' decisions to rely largely on the draft rather than on the reserve forces, joining a Guard or Reserve unit became a way to avoid service in the Vietnam War, although 42 Army Reserve units were called up with 35 of them deployed to Vietnam shortly after the Tet offensive in 1968–69, 5760 reservists dying in the conflict. Before graduating from Yale in 1970, Bolton enlisted in the Maryland Army National Guard rather than wait to find out if his draft number would be called. (The highest number called to military service was 195. ) He saw active duty for 18 weeks of training at Fort Polk, Louisiana, from July to November 1970. After serving in the National Guard for four years, he served in the United States Army Reserve until the end of his enlistment two years later.