As an enlisted man in the Army Air Forces for almost two years, he completed both aircraft mechanic and aerial gunnery training on B-17s and B-24s prior to his appointment to the academy.

From September 1954 to June 1956, Marsh attended the University of Michigan under the Air Force Institute of Technology program.

He completed his tour of duty at the Pentagon as executive officer for the deputy chief of staff for research and development.

In September 1969 Marsh returned to Wright-Patterson Air Force Base as deputy for reconnaissance, strike and electronics warfare.

In June 1973 he received his first assignment to Air Force Systems Command headquarters as deputy chief of staff for development plans.

He was commander of the Electronic Systems Division, Hanscom Air Force Base, Massachusetts, from May 1977 to January 1981.