Carpetbagger aircraft flew spies called "Joes" and commando groups prior to the Allied invasion of Europe on D-Day and afterward, and retrieved over 5,000 officers and enlisted men who had escaped capture after being shot down. The low-altitude, nighttime operation was extremely dangerous and took its toll on these airmen. The first aircrews chosen for this operation came from the anti-submarine bomb groups because of their special training in low altitude flying and pinpoint navigation skills. Because of their special skills, they were called upon to fly fuel to General George Patton's army during the summer and early autumn of 1944 when it outran its fuel supply. When this mission was completed, it was recorded that 822,791 US gallons (3,114,264 L) of 80 octane gasoline had been delivered to three different airfields in France and Belgium.