McGaha fought in the Guadalcanal Campaign and the northern Solomons before participating in the campaign to recapture the Philippines from Japanese control. On February 7, 1945, he was serving as a master sergeant during the Battle of Luzon. On that day, near Lupao, Luzon, he repeatedly exposed himself to enemy fire in order to aid wounded soldiers, led his platoon after the platoon leader was wounded, and deliberately drew Japanese fire onto himself so that others could escape to safety. For these actions, he was nominated for the Medal of Honor and given a battlefield commission to second lieutenant. McGaha was then discharged from the Army, but soon re-enlisted as a master sergeant and was stationed at Fort Benning, Georgia. His nomination for the Medal of Honor was approved a year after the battle, on April 2, 1946. During a ceremony at the White House on March 27, 1946, President Harry S. Truman formally presented McGaha and another man, Navy Commander Richard O'Kane, with Medals of Honor.