On 14 October 1943 the US 8th Air Force attacked the ball-bearing factories at Schweinfurt in central Germany, an industry which was seen as a bottleneck in the German industrial manufacturing system. The raid had led to the German air defences inflicting many losses on the bombers but the city and the industry were severely hit.
The attack on Fortress Koepenick
On 20 October, just a week later, the 8th Air Force sent 119 bombers to attack the town of Düren, near the border city of Aachen. The Americans reached their target and bombed it, after which they turned for home. At this point German observers reported a large formation of aircraft heading south. In 1973, Alfred Price wrote that this was based on the noise of aircraft, though they were not seen; Adolf Galland attributes this to chaff dropped by the bombers drifting on the wind and registering on German radar. When it was reported to Hermann Göring, the Luftwaffe leader, the attack on Düren was seen as a ruse and another devastating attack on central Germany was assumed to be underway. The Reichmarschall took command of the air defence and ordered all available fighter aircraft to intercept. As these fighters became airborne and could be heard from the ground or reported by radar, the impression of a huge force of attackers heading south became more pronounced. As they were on the same course as the force that attacked Schweinfurt less than a week before, Göring inferred that this was the target and ordered the fighters to intercept there. As the phantom bombers passed over Schweinfurt without any ill effect, Göring decided that they were heading for Leuna, the synthetic fuel refinery near Leipzig, another sensitive target. When again there was no bombing, Göring suspected an attack on the Skoda Works at Pilsen and diverted the fighters there. By this time, the fighters were running out of fuel and as the defence system dictated, started to land at the nearest available airfield. As the fighters landed, the attacking force began to melt away. Galland wrote that the sky was clear over Pilsen and ground observers could see there were no bombers, only German fighters. With this, the phantom raid evaporated.
With the disappearance of the threat, Göring freely admitted the laugh was on him, that he had sent the Luftwaffe on a mammoth tour of their own airspace and sent an ironic telegram to all concerned congratulating them and himself on "the successful defence of the fortress of Koepenick", a reference to a notorious hoax of the early 20th century. Price and Galland pointed out the difficulties of discriminating between friend and foe in confused circumstances; both observed that neither side managed to resolve the problem during the air war.