The Bombing War: Europe 1939-1945

The bomber arm, which would bear the brunt of the eleven-month campaign, was equipped with three aircraft types: two of them, the Dornier Do17Z and the Heinkel He111H/P, had first been developed in 1934–5 and were now nearing obsolescence. They were relatively slow, poorly armed and could carry over most of the distances required between 2,200 and 4,000 lbs of bombs; the third was the more recently developed medium bomber, the Junkers Ju88A, which first saw service on any scale in August 1940 and soon became the principal bomber model as the Do17 and He111 were gradually phased out. The Ju88 had been welcomed in the late 1930s as a versatile and effective aircraft, also capable of a reconnaissance and night-fighter role, but it was plagued with development problems and only in the autumn of 1940 did it start to appear in quantity.⁶³ But instead of the promised speed and enhanced striking power, the Junkers bomber, like the ones it was designed to replace, carried a modest defensive armament, flew at around 280 miles per hour and could carry little more than the existing aircraft, around 4,000 lbs of bombs, with even smaller weights for longer flights.⁶⁴ Confidence that the Ju88 would fulfil all immediate requirements meant that there was no heavy bomber available in 1940, though they were in the pipeline. The Heinkel He177 multi-engine long-range bomber commissioned in 1938 was still in an early development stage, which left nothing except for the slow Focke-Wulf Fw200 ‘Condor’, a converted airliner that was used to good effect in the early stages of the war against shipping, but was far too vulnerable to risk in overland attacks. The small German bombers also carried relatively small bombs, principally the 50-kg or 250-kg fragmentation bomb, with a high charge-to-weight ratio, the 1,000-kg landmine, and the 1-kg incendiary bomb, packed in cases of 36 bombs each. Loaded with thermite (a mixture of ferrous oxide and powdered aluminium), and with a casing of magnesium alloy, the incendiary core burned for around a minute, the casing for twelve to fifteen minutes.⁶⁵

The bombers enjoyed the benefit of sophisticated methods of electronic navigation developed in Germany in the 1930s. The Knickebein (crooked leg) system, pioneered by the German Telefunken company, used two beams of radio pulses sent from separate transmitters. One sent Morse dashes, one dots. When the two merged, the aircraft was at the point to release the bombs. The beams were based on the Lorenz blind-landing equipment developed in the 1930s to guide aircraft back to an airfield at night or in poor weather. The second system, known as X-Gerät (Equipment X), was more complex. It utilized six Lorenz beams, three pointing at the target, three designed to cross them at intervals, the first 50 kilometres away from the objective, the second 5 kilometres away and the third just before the actual target zone. A timer activated on the aircraft automatically released the bombs at precisely the pre-calculated distance. In November 1940 Y-Gerät was added using just a single beam, which relied on signals sent back from the bomber to calculate its range. When the ground station was satisfied that the aircraft was precisely over the target, it transmitted an automatic bomb release.⁶⁶ The Knickebein method could be used in any bomber with blind-landing equipment, the X- and Y-Gerät only by specially converted aircraft. Experimental training began in 1938, and in late summer 1939, before the invasion of Poland, the new units were established as Kampfgruppe 100, Bomber Group for Special Operations, directly under Göring’s control.⁶⁷ It was found that both systems could achieve a remarkable level of accuracy under the right conditions, in marked contrast to the poor navigational prospects for the RAF. Around 30 to 40 Heinkel 111s fitted with the new equipment were used to undertake pinpoint attacks or to act as a vanguard for a larger force by dropping flares and incendiaries in the target area. In the spring of 1941 a second unit was activated, Kampfgruppe 26, designed to use the Y-Gerät. Transmitter stations were set up from Stavangar in Norway to Cherbourg in western France, a total of seven by the summer of 1941.⁶⁸