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Adlerstag, Knickebeins, and Bletchey Park: Britain, Ultra, and the Battle of Britain, 1940

© Joseph Sramek

One further thing should be said about the Knickebein beams. Luftwaffe Command regularly sent out Knickebein information via the Enigma machine. By the summer and fall of 1940, the Luftwaffe cipher was being promptly deciphered by Bletchey Park. Through the Knickebein beams, the British knew where the German targets were. Thus it was possible to take measures to prevent the bombing of these targets, or to minimize damage caused to them. In one historian's eyes, this fact alone was the decisive reason for Germany's loss of the Battle of Britain. [9]

One of the more important engagements during the Battle of Britain was "Adlerstag," or "Eagle Day." On August 8, 1940, Hermann Göring, the head of the Luftwaffe, sent battle instructions to his three Air Fleets which were promptly picked up on Ultra. The Battle instructions were as follows: "Operation Adler. Within a short period of time you will wipe the British Air Force from the Sky. Heil Hitler." [10 Because of bad weather, the massive raids were postponed. When the raids finally happened a week later, the British were ready.

The air battle that took place on August 13 and 14, 1940, was, in many ways, the turning point of the Battle of Britain. As the Luftwaffe Air Fleets proceeded to follow Göring's order, RAF planes went up in significant numbers and in the right places. They were guided by radar and by Ultra, as Göring and the Air Fleets planned strategy and signaled through Enigma during the battle. [11] By using Ultra, Sir Hugh Dowding (the Commander of the RAF) was able to carefully apportion his resources and defeat the German onslaught. As a result, the Luftwaffe suffered three times as many losses as the RAF during the course of the battle. [12]

The information that Dowding received through Ultra clearly enabled him to achieve victory. As far as its immediate contribution to victory in the Battle of Britain, Ronald Lewin asserts that this information was the daytime equivalent to that received about the Knickebein beams. It was instrumental in bringing British victory in the Battle of Britain. [13]

By the end of September the Germans began to believe that victory in the Battle of Britain was not likely, at least not in 1940. The Germans shifted their targets to population centers, and postponed Operation Sea-Lion. By mid-October, the English knew that Hitler had canceled the invasion through an important Enigma signal that announced the disbanding of the invasion staff. [14]