Gunners and belts of ammunition fed to the beam guns of a Boeing B-17 Flying Fortress, the four-engined heavy bomber used by the United States Eighth Air Force, mostly based in southern England. The B-17 was primarily employed by the USAAF in the daylight strategic bombing campaign against German industrial and military targets, but also complemented the RAF Bomber Command's nighttime area bombing in the Combined Bomber Offensive to help secure air superiority over the cities, factories and battlefields of Western Europe in preparation for the invasion of France in 1944. - Stock Photo