In 1943, the USAAF and RAF launched the Combined Bomber Offensive, designed to systematically destroy the industries that the German war machine relied on. At the top of the hit list were aircraft factories and plants making ball-bearings - a component thought to be a critical vulnerability. Schweinfurt in southern Germany was home to much of the ball-bearing industry and, together with the Messerschmitt factory in Regensburg, which built Bf 109 fighters, it was targeted in a huge and innovative strike.Precision required that the targets were hit in daylight, but the raid was beyond the range of any existing escort fighter, so the B-17s would go in unprotected. The solution was to hit the two targets in a coordinated ''double-strike'', with the Regensburg strike hitting first, drawing off the defending Luftwaffe fighters, and leaving the way clear for the Schweinfurt bombers. The Regensburg force would carry on over the Alps to North Africa, the first example of US ''shuttle bombing''.
