Decoding Nazi Secrets

Decoding Nazi Secrets (Nova/WGBH & Channel 4, 1999) This is an extraordinary, meticulously-detailed , two-hour documentary on how the British developed an ongoing capability to decipher the German ENIGMA code. Apart from the cipher setbacks and triumphs, for the historian the most significant insights are how ENIGMA breakthroughs affected key military operations in the European and North African theaters of World War II. Comments from former employees of Bletchley Park, Britain’s codebreaking center, enhance the authenticity of this seminal historical account.

    In 1938 the British Code and Cipher School was relocated to Bletchley Park. What was needed was a new approach to codebreaking. Swiftly an unusual assortment of mathematicians, anthropologists, paleontologists, and others who had a knack with crossword puzzles was assembled. Their overriding task was to crack the ENIGMA code, which the Germans considered unbreakable. This was a formidable task, given the three-rotor system and the astronomical possibilities posed by any single message.

    Initially these codebreakers came up with nothing. Between 1931 and 1938 a disgruntled German clerk had collected hundreds of ENIGMA-related documents which he had sought to peddle, to no avail, to the French, then the Britain. Poland, fearful of German intentions, bought the packet and established a first-class codebreaking operation. Then, in 1939, they were stymied, when the Germans attached an additional rotor.

    Just before Germany invaded Poland, the Poles invited French and British cryptographers to their facility and arranged to have their ENIGMA machines smuggled out to England. The Poles provided an essential clue as to how to decipher the latest German messages.

    The first major British ENIGMA success permitted the British fleet in the Mediterranean to deal a near-mortal blow to the Italian fleet. Shortly thereafter a change in the German system totally stymied British cryptographers.  The next British ENIGMA breakthrough related to Luftwaffe traffic. Thanks to operator error, Bletchley House was able to read Luftwaffe for the remainder of the war.

    The importance of the Battle of the Atlantic gave highest priority to breaking of the German naval code. Thanks to Alan Turing, a mathematic genius, significant progress was achieved. The capture of the U-110’s code material swiftly permitted the reading of U-boat messages. The first military success was the diversion of a June 23, 1941 convoy that would have been a sitting duck for a 10 U-boat wolf pack.

    In February, 1942 a change in German naval codes rendered their messages indecipherable. Massive North Atlantic shipping losses resulted. Ten months later,
Once  Bletchley Park was able to crack this new four-rotor code, the vital Atlantic logistical life line became far more secure. [The impact of Bletchley Park’s ability and inability to read U-boat codes is reflected in quarterly totals of tonnage sunk by U-boats in the North Atlantic:  October-December, 1942 1,679, 393; October-December, 1943: 250,959; October-December, 1944: 95,286.]
    Another dramatic Bletchley Park success occurred in North Africa. German General Erwin Rommel had been threatening to capture Egypt and the vital Suez Canal. By reading German ENIGMA messages as well as Italian communications, the British had timely and precise knowledge of Rommel’s forces and logistical requirements. While preserving the absolute secrecy of ENIGMA intercepts, the British still were able to destroy nearly two-thirds of the shipments sent to Rommel’s forces. Having Rommel’s order of battle provided General Montgomery an extraordinary advantage in the critical El Alemain battle. For a while, Rommel also received the daily British order of battle, from codes that were stolen from the American embassy in Rome. A comprehensive historical analysis of this campaign would require knowledge of the communications intelligence available to both adversaries. [Brigadier Desmond Young’s highly acclaimed Rommel: The Desert Fox (1950) lacked such knowledge; as of January 3, 2008, the Wikipedia account of Rommel’s North African campaign  fails to mention communications intelligence.]

    For over a year the British were unable to decipher  a new German code they named Lorenz. It was a diabolically complex code ordered by Hitler for his communications with the German military. Thanks to a German operator error on August 30, 1941, a cipher breakthrough was accomplished. Since it still took up-to-a-month to decipher a single message, the tactical advantage of such messages was minimal. Thomas Powers, at the Post Office Research Station, envisaged a massive machine that became the first programmable computer.

    The Colossus, as his monster was named, was able to decipher Lorenz messages in minutes. Starting from five months before D-Day, this provided the Allies remarkable insight into Hitler’s communications with his German generals. [For security reasons, the British never permitted publication on any aspect of Mr. Flowers’ invention. In 1960 he was ordered to destroy all documentation on the development of Colossus and the final two machines were destroyed. He seems to have a valid claim that his invention, rather than ENIAC, was the first programmable computer.]

    Bletchley Park was of vital importance in the planning and deception related t o D-Day. The Allies conducted a massive disinformation campaign to persuade Hitler that Calais rather than Normandy was the primary D-Day landing sight. Through reading of German messages, the Allies had continuing assurance that the Germans were deceived. Also, just before parachutists were dispatched,  Bletchley Park deciphered a German message that placed a major German force at the landing spot for Allied parachutists. They were redeployed. That the codebreakers were able accurately to identify the location of 60 of the Germans 62 divisions greatly facilitated a successful landing.

    The Bletchley Park accomplishments of Alan Turing, who is described as a brilliant and original thinker who discovered fundamental elements vital to computers and the Internet,  are not dwelt on in this documentary. A fuller account can be found in Breaking the Code (Mobil Masterpiece Theatre, 1997).

    The documentary concludes that:

    Curiously, one aspect about Bletchley Park that is noted elsewhere is ignored in this documentary. It appears that by the summer or early fall of 1940 the British, through communications intelligence, had credible information that Hitler had called off a prospective invasion of England and was turning eastward towards Russia. My understanding is that this information was not forwarded to the Americans, then at peace, for at least three or four months.

    There is also a useful Decoding Nazi Secrets  web site at

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