The atomic bomb was dropped on Nagasaki, Japan on August 9, 1945, but while the Allies awaited Japan's response to the demand to surrender, the war continued. On August 13, 1945, 1st Lt. Perdomo shot down four Nakajima Ki-43 "Oscar" fighters and one Yokosuka K5Y "Willow" Type 93 biplane trainer. This action took place near Keijo/Seoul, Korea when 38 Thunderbolts of the 507th Fighter Wing encountered approximately 50 enemy aircraft. This action was Lt. Perdomo's tenth and final combat mission, and the five confirmed victories made him an "Ace in a Day" and earned him the distinction of being the last "Ace" of World War II. He was awarded the Distinguished Service Cross for extraordinary heroism in action and the Air Medal with one oak leaf cluster.