Walmsley rose to the rank of captain and posthumously received the Medal of Honor for his heroic actions on September 14, 1951, above Yangdok, North Korea during a bombing mission.Born in Baltimore, Maryland, Walmsley joined the Army Air Forces and spent the 1940s as an instructor pilot in the United States and Japan, but did not see combat.A September 12 raid was extremely successful; in it, Walmsley's B-26 attacked a convoy with 500 pounds (230 kg) bombs, destroying or damaging 16 trucks, and forcing many of the vehicle drivers off the road.The aircraft was crewed by Walmsley as well as bombardier/navigator Second Lieutenant William D. Mulkins, photomapper Captain Philip W. Browning, and air gunner Master Sergeant George Morar.[6] As the aircraft neared Yangdok, 100 miles (160 km) behind North Korean lines, the crew spotted an armed locomotive hauling supplies south in the middle of the night.He immediately attacked, producing a strike which disabled the train, and, when his ammunition was expended, radioed for friendly aircraft in the area to complete destruction of the target.Directing an incoming B-26 pilot, he twice boldly aligned himself with the target, his searchlight illuminating the area, in a determined effort to give the attacking aircraft full visibility.Walmsley descended into the valley in a low level run over the target with searchlight blazing, selflessly exposing himself to vicious enemy antiaircraft fire.His heroic initiative and daring aggressiveness in completing this important mission in the face of overwhelming opposition and at the risk of his life, reflects the highest credit upon himself and the U.S. Air Force.