Staff Sergeant Duncan was a crew member of a B-29A Superfortress Bomber with the 325th Bomber Squadron, 92nd Bomber Group. On 9 September 1950, while on a bombing mission, his aircraft was hit by anti-aircraft fire and exploded mid-air near Wolbong-ni, South Korea. Five parachutes were seen. He was taken Prisoner of War and was presumed dead on 31 March 1954. His remains were not recovered.

Duncan was awarded the Air Medal with 4 Oak Leaf Clusters, the Purple Heart with Oak Leaf Cluster, the Prisoner of War Medal, 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.