Private Marshall was a medic with the Medical Company, 17th Infantry Regiment, 7th Infantry Division. He was listed as Missing in Action while tending his wounded comrades in North Korea on 18 April 1953. He was presumed dead on 19 April 1954. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Marshall was awarded the Purple Heart, the Combat Medical Badge, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.