Don Ringgenberg was inducted into the U.S. Army Reserves during his senior year of high school in 1956. He received his basic training in Fort Leonard Wood, Missouri, and served in Fort Polk, Louisiana, with the Second Howitzer Battalion from July 1957 to December 1957. He also served on active duty in Fort Sill, Oklahoma, in 1961 (during the Berlin Crisis) in an artillery unit. He was honorably discharged from the Army Reserves on May 13, 1964.