German Anti-Aircraft Defences
Germany fought bitterly to defend its territory, using fighters, anti-aircraft artillery and a whole range of detection and scrambling devices. Both sides conducted intensive research work to improve radars and counter-measures against enemy technologies; all this made the bomber war a form of sophisticated electronic warfare.
During the Battle of Britain, the British protected themselves against German bombing raids through an early warning system, the Chain Home, and by using fighters-interceptors. Germany used a similar combination, a radar network that warned fighter-interceptor squadrons of the impending arrival of enemy bombers.
As soon as Allied bombers came close to the German shores of the North Sea, the Freya early-warning radar network detected them. A second network, called Würzburg, followed their course as they flew towards their targets. By day, fighters could locate bombers visually and attack them. By night, however, the situation was quite different: a third radar network was used by ground controllers to guide the Nachtjagdgeschwader (“Night Fighter Squadron”) pilots – usually flying twin-engine Messerschmitts Me 110, Junkers JU-88G or Heinkels He 219 – towards Allied bombers until they picked them up on their airborne radar screens (“Lichtenstein”) or actually saw them. Under cover of darkness, the fighters then closed on their targets and, when the moment was right, attacked from behind and from below, the blind spot that bomber gunners cannot reach from their turrets. That approach was so deadly that German engineers equipped night fighters with dorsal turrets with twin 30-mm guns pointing upwards. A fighter aircraft thus provided with that “Schräge Musik” (literally “slanting music”, or “jazz”) could fire at a bomber before being spotted.
- Brereton Greenhous et al., The crucible of war, 1939-1945: History of the Royal Canadian Air Force Volume III, 1994.
Warned by Freya and Würzburg, the Flak (Flugabwehrkanon, i.e., anti-aircraft artillery) was waiting, prepared and resolute. Its 20-, 37- and 88-mm anti-aircraft guns were aimed at the sky and, as soon as the bomber came within reach, hundreds of shells were fired, filling the sky with smoke balls, that hung motionless. An 88-mm shell exploding within 10 metres of a bomber could be fatal. In the dark of the night, some guns were radar-controlled and guided the manually controlled guns. Light and medium Flak could be avoided by flying at higher altitudes but this had an impact on bombing accuracy. Since no one could guess where the next shell would explode, to the right or to the left, in front or behind the plane, bomber pilots were instructed to stay their course and avoid evasive tactics that rendered navigation more difficult and reduced bombing accuracy.
Bombers could also encounter another anti-aircraft system, maybe the most formidable of all. Radar-controlled searchlights swept across the night sky, suddenly lighting up and zeroing in on an enemy aircraft. As soon as a searchlight found a target, others, manually controlled, were turned on, enclosing the incoming bomber in a cone of light that followed it relentlessly. Pilots, blinded by the searchlights, made desperate attempts to escape the light beams. If they were not successful, the trapped bomber became an easy prey for the Flak or for night fighters.Since bombing operations were conducted by night, pilots, navigators and bombers relied on electronic devices to find their way, to identify targets and to detect enemy aircraft in the dark. German and British engineers tried to outdo one another in their attempts to improve navigation systems and foil enemy detection systems.
For instance, during the great air raid against Hamburg in July 1943, Allied bombers dropped thousands of small pieces of metallic foil, called Windows, with a length that matched the wavelength of German radars, causing radar screens to fill up with a myriad of (almost entirely) bogus echoes.
Devices were developed that could detect enemy radar or wireless signals, thus providing data on their location. The Germans invented a system that could spot signals from the airborne Allied H2S radar, used for navigation on night bombing operations. Luftwaffe fighters could then follow that signal and were sure to intercept the target bomber. Other devices were used to scramble enemy radars or wireless signals used for communications.
Until 1945, measures and counter-measures followed one another, but in that rapidly evolving electronic warfare, neither the Allies nor the Axis were able to gain a definite advantage.