In June 1951, Walmsley was assigned to the
8th Bombardment Squadron,
3rd Bombardment Wing,
Fifth United States Air Force which flew the
Douglas B-26 Invader in Korea during the
Korean War. During this time, he was described as "cheerful and popular". During the early phase of the war, missions included fairly simple bombing runs with
fragmentation bombs and
.50 caliber machine guns. The arclights, with an estimated 80 million
candlepower, would easily illuminate supply trains but also expose the UN aircraft to
antiaircraft fire. As the aircraft neared Yangdok, behind North Korean lines, the crew spotted an armed
locomotive hauling supplies south in the middle of the night. Walmsley immediately had his crew attack the locomotive. They expended their complement of bombs in striking the locomotive, damaging it but not stopping it. Walmsley then called in another B-26 Invader from Kunsan, and upon its arrival volunteered to illuminate the locomotive with his aircraft's arclight. Walmsley's aircraft passed over the locomotive three times, illuminating it but, taking antiaircraft fire in the process from both the train itself and emplacements along the rail line, damaging the aircraft. Walmsley's actions not only illuminated the train but also allowed his aircraft to absorb most of its fire, sparing the other aircraft from attack. He did not take any evasive action against the North Korean anti-aircraft fire so as to keep the train illuminated for the other American aircraft. After the third pass, the train was destroyed by the combined firepower of the two bombers, together with its cargo. However, Walmsley's aircraft was severely damaged. Its wings began trailing fuel, which ignited. Walmsley's aircraft caught fire, and proceeded about , fighting to maintain altitude before finally crashing into the ground in a mountainous region, killing Walmsley, Mulkins and Browning, and severely injuring Morar. As the lone survivor of the crash, Morar was captured and spent the remainder of the war in a prison camp, though he survived. Walmsley was declared
missing in action after the mission, and his status was listed as "presumed dead" after the end of the war. Walmsley's crew each received a
Distinguished Flying Cross for extraordinary heroism. Walmsley however, was awarded the
Medal of Honor posthumously on June 12, 1954. The medal was presented to his widow at
Bolling Air Force Base in
Washington, D.C. Four weeks after the mission, the arclights and Operation Strangle were abandoned, as leaders felt the risks and casualties of the operation outweighed the benefits. == Medal of Honor citation ==