On July 24, 1945, Guinn led his division of eight Hellcats during the Attacks on Japanese Naval Anchorage, Kure, Honshu. He skillfully piloted his aircraft in a determined attack against Japanese cruiser "Aoba" docked in the harbor and despite heavy anti-aircraft fire from enemy warships and ground installations, he scored a direct hit on the fantail of the ship with 2,000 lb bomb, which contributed to the sinking of that vessel. For this act of valor, Guinn was decorated with Navy Cross, the United States military's second-highest decoration awarded for valor in combat.