Walmsley was awarded the Medal of Honor posthumously for the daring risks he took to drop bombs on targets during the Korean War. Walmsley, a former flight instructor, piloted a B-26 belonging to the 8th Bombardment Squadron. He was developing strategies for searchlight attacks against enemy convoys.
Korea was resupplying its army overnight through truck and train convoys. One night, Walmsley discovered an enemy supply train near Yankgdok, Korea, as he flew over. This train was a high value target, according to a report. Walmsley identified and dropped bombs on the train, eventually running out. The train, as a result, was disabled.
Instead of returning to base, Walmsley called for more friendly aircraft to complete the destruction of the train. While flying, he used his searchlight to expose the train. This, however, made him an easy target for the enemy. Walmsley made two low-level passes over the top of the train to guide the other B-26s. Before he could complete another pass, his plane took enemy fire. The damage to the aircraft was catastrophic and he crashed into the mountains nearby. Walmsley was a combat veteran and had already completed 25 combat missions. His courageous actions allowed his comrades to continue the fight even at the cost of his own life. Walmsley was posthumously awarded the Medal of Honor June 12, 1954.