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

© Joseph Sramek

The Battle of Britain began in the summer of 1940, right after the collapse of France. It lasted through the end of October when the Blitz began. The battle was fought over whether the Germans would gain air supremacy over England. Had they achieved this, Operation Sea-Lion, the planned invasion of England, would have followed.

What many today fail to realize is that this was a very close-run thing. In the spring of 1940, British cryptologists broke the German Luftwaffe code, otherwise known as Enigma. The impact of this discovery on the ensuing Battle of Britain and the remainder of World War II was immense. In many ways, it helped to tip the scales of victory in the Allies favor.

In 1974, when Ultra was first de-classified by the British Government, F.W. Winterbotham published his The Ultra Secret. In it, he argued that Ultra was the only thing that saved the RAF from defeat at the hands of the Luftwaffe. [1] On the opposite side of the spectrum, F.H. Hinsley wrote in his British Intelligence in the Second World War, the Official History:

That Germany lost the battle and was forced to abandon the attempt to land in England - this outcome, contrasting with her successes so far owed much to the difficulty of the German undertaking and perhaps still more to the tenacity of the British resistance. It owes less to the fact that British intelligence was at last beginning to improve. [2]

The complete contrast between the two positions aptly demonstrates the difficulty of answering the question possed above definitively. It can be reasonably assumed, however, that the answer lies somewhere between these two positions. It is this "grey area" that I will now explore.

The Germans did a significant amount of their bombing during the night, particularly toward the end of the conflict and during the Blitz. For obvious reasons, this posed navigational difficulties when they tried to find targets, especially non-London ones. For this reason, a radio based navigation system known as Knickebein was developed. [3]

The Knickebein system consisted of two intercepting beams, one which used dots and another which used dashes (for use in Morse Coade). These beams were used by German pilots to find their bombing targets. The Knickebein navigation system provided remarkable accuracy, usually within 400 feet of the intended target. [4] The Germans had 12 Knickebein radio beam transmitters located throughout the occupied Low Countries and France. [5]

On June 12, 1940, Bletchey Park intercepted an Enigma message. All it said was: "Cleve's Knickebein is beamed at position 53 degrees 24 minutes north and 1 degree west." [6] But this is what R.V. Jones, the Assistant Director for Scientific Intelligence at the Air Ministry, was searching for. [7] He began working on a plan to thwart the Knickebein system. The plan that was developed entailed jamming the Knicekbein beams, by sending out dashes on the same frequency as the beam. This induced a great loss of confidence and morale in the Luftwaffe ranks, and led to less damage occurring. [8]