McKinney was serving in Company A 123d Infantry Regiment, 33d Infantry Division in the Philippines when he and two of his comrades were snuck up upon by over 100 Japanese soldiers. The three American troops were guarding a machine gun at the time and the other two American soldiers were wounded before they could aid in the fight.
Single handedly and armed with only a rifle, McKinney killed 38 Japanese soldiers, successfully holding the broken machine gun until aid arrived. He was able to hold off the rest of the soldiers until help came. He survived with only a minor head wound and was awarded the Medal of Honor by the President of the United States.