 Complete the following phrase:  The B-17 was primarily employed by the USAAF in the daylight strategic bombing campaign of World War II against German industrial, military and civilian targets. The United States Eighth Air Force, based at many airfields in central, eastern and southern England, and the Fifteenth Air Force, based in Italy, complemented the RAF Bomber Commands night-time area bombing in the Combined Bomber Offensive to help secure air superiority over the cities, factories and battlefields of Western Europe in preparation for 