From 1980-83 he served as Commandant of the Kansas Military Academy, Salina, Kansas. Following over 15 years of command, he was assigned as Director of Plans, Operations, and Training for the Kansas Army National Guard. His final assignments were as Deputy Director, State Area Command, and Asst. Adjutant General-Army and commander of the Kansas Army National Guard. He retired in 1998.

During his career, he served as president of both the National Guard Association of Kansas and the STARBASE Board of Directors; as chairman of the Kansas Army National Guard Council; as a member of the Board of Directors of the Museum of the Kansas National Guard, the Officer Candidate School Hall of Fame Board, and the Kansas Military Advisory Board; and as the 5th Army representative on the National Guard Bureau Quality Advisory Council.

General Gerhardt's awards include the Legion of Merit, Meritorious Service Medal with Oak Leaf Cluster, Army Commendation Medal with Oak Leaf Cluster, Adjutant General's Award of Excellence, and numerous other federal and state awards.

General Gerhardt graduated with an EDD in education and served over 39 years as principal. He was active in his local PTO. As a part-time Guardsman and fulltime school administrator, he was a champion of the citizen-soldier. He was active in many community, church, and political organizations, and ensured that the voice of the traditional Guardsman was heard as decisions were made affecting the Guard. He was instrumental in bringing the "quality management" concept to the Kansas Guard, in encouraging personnel strength in the units, which he commanded, and in ensuring that all units met standards through the Command Inspection and Mobilization Readiness programs which he led. In retirement he devoted considerable energy to preserving the Kansas militia heritage in the Museum of the Kansas National Guard. He was inducted into the Hall of Fame on 4 November 2007.