Charles Leonard Duncan served in the United States Marine Corps as a pilot from 1942 to 1961. He served during World War II as an aerobatics instructor in Pensacola, Florida, before returning home to Missouri but remaining in the Marine Corps Reserve. In 1952, Duncan was summoned once again for active Marine service in Korea and later Japan. He completed 54 combat missions during the Korean War. During his deployment, Duncan documented his experience in Korea and Japan through photographs, records, and letters to his wife, Mary. Duncan returned home to the United States in 1953, where he then served in the Marine Corps Reserves until his retirement as a major in 1961.

Duncan was born in Sewickley, Pennsylvania, on November 12, 1919, the son of Alvis and Ida Mae Duncan. He was raised in Belleview, Missouri, and graduated from the Junior College of Flat River, in Flat River, Missouri, an affiliate of Southeast Missouri State Teachers College, in 1942. He married Anna Mary Ricketts in 1944, and couple had four children: Sandy, Steve, Kim, and Kay. Alongside his military career, Duncan owned a limestone quarry business as well as a ready-mix concrete operation and developed shopping centers. After his military retirement, he also entered a career as a real estate broker which continued until shortly before his death. He continued to fly throughout his life and later in life was commissioned for a government agricultural tour throughout Europe and Russia. Duncan died on June 29, 1995, at Piedmont, Missouri, and was buried in the Piedmont Masonic Cemetery.