Title:                  Enigma

Author:                Gustave Bertrand

Bertrand, Gustave (1975). Enigma; ou, La plus grande énigme de la guerre 1939-1945. Paris: Libaririe Plon

LCCN:    73168841

D810.C88 B47


Date Updated:  March 26, 2015

This book originally appeared in French (Enigma; ou, La plus grande énigme de la guerre 1939-1945). As far as I can tell it has not been translated into English (English title would be b Enigma, or, The Greatest Enigma of the 1939-1945 War.

Maintaining the Secret

Two words describe the German WWII fighting machine successes: organization, and communication. Their lightning “blitzkrieg,” which allowed them to roll over Europe almost unopposed, was a well coordinated operation employing Panzers and Stukas (dive bombers). At sea, their efforts were aimed at cutting England’s supply line from North America by well directed submarine “wolf pack” attacks on convoys. For communications, the Germans relied almost entirely on messages sent by radio. These messages could be heard, of course, by anyone equipped with a receiver.

To ensure that the enemy would not intercept vital information, the Germans used an electro-mechanical device called Enigma to encode the messages. They believed that even if the enemy were to capture a machine, it would be useless unless both sender and receiver were also in possession of the same key which specified how the machine was set for the day to encrypt messages. The Poles proved them wrong. The Germans used different radio frequencies and keys for messages sent to their various units. This ensured that messages meant for the Luftwaffe were not readable by the Kriegsmarine (Navy). By assigning different keys to different units, communication could be directed to the appropriate unit. Not only would there be no point in a submarine decoding a message meant for a panzer unit, but some ultra-secret messages (for example to the SS) were confidential.

What Went Wrong?

Enigma codes could have been unbreakable, at least with the methods available at the time, had the machine been used properly. The biggest mistake the Germans made was their blind belief in the invincibility of Enigma. Procedural errors in using the machine, combined with occasional operator laziness, allowed the Poles and, subsequently the British (much later), to crack the “unbreakable” codes. In addition to the general key, a “message key”, unique to each message, was part of the transmission. Each army unit had two enigma operators, one to work the machine, the other to write down the illuminated letters on the lamp board. Often, these men were not properly trained in the use of the machine. They were allowed to pick their own message keys, at times making some very poor choices.

The navy had better safeguards – only officers were allowed to set up the machines. The message keys were specified and carefully chosen to minimize the possibility that they could be deduced by the code breakers. The code lists were printed with water-soluble inks and kept under lock and key at all times. The Navy’s extra precautions were effective; the Allies were unable to crack the naval codes until two years after they had broken the army’s.


“Hans Thilo-Schmidt, originally of a German aristocratic family, had fallen upon hard times. He persuaded his brother, a Lieutenant Colonel in the German signal corps to give him a job. One of his tasks was to destroy Enigma codes which were no longer valid. His security clearance granted him access to information which he decided to sell to the French. His first contact was made in 1931. He furnished Gustave Bertrand of the French Intelligence service, the author of this current book, a booklet detailing the Enigma machine setup procedures. There was no mention of the rotor wiring or information on the keys.

In fact, what Schmidt handed over was more than a booklet. He provided seven documents with two highly important ones: User Manual for Enigma, and Enciphering Procedure for Enigma with drawings and pictures. The French puzzled over this information, then consulted with the British, who agreed that it was insufficient to be of any practical use. No one knows why this valuable information was rejected. Bertrand then offered it to Lt. Col. Langer, head of the cipher office in Poland, who was overjoyed upon receiving even this small crumb. Rejewski (one of the three Polish mathematics experts) asked Bertrand if he could obtain some outdated Enigma keys. The Frenchman relayed this request to Schmidt who readily obliged, and the keys were passed back to Poland.

With keys given them by the French, and using replica machines they had built, the Polish team of Marian Rejewski, Jerzy Rózycki and Henryk Zygalski were able to decode most German messages. They were particularly interested in radio traffic between German troops training in Russia, a ploy which allowed them to circumvent terms of the Versailles Treaty. However, they never related their results to the French, probably because they feared the Germans would find out that their codes had been compromised and institute new procedures which would nullify their success. The French, puzzled at receiving no intelligence, continued to pass on the keys nevertheless.

The Poles began their efforts when the Germans used only three rotors. Although the keys were out of date, they were able to apply them to a backlog of messages. Having made the first replica of Enigma, they launched an industrial production of this machine by the AVA factory for radio equipment. The first industrial replica came out of the factory in 1934 and by 1939 they had 17 machines, two of which were handed over to French and British in August 1939.


On Dec. 15 1938, the Germans added two new rotors, making five available, although only three were used in the machine at any one time. The Polish resources were severely strained, as now 60 sets of Zygalski sheets and 60 bomby (at a cost of 1.5 million zlotych, about $350,000) would have been required. The method of Zygalski sheets was a cryptologic technique used by the Polish Cipher Bureau before and during World War II, and during the war also by British cryptologists at Bletchley Park, to decrypt messages enciphered on German Enigma machines. The Zygalski-sheet apparatus takes its name from Polish Cipher Bureau mathematician–cryptologist Henryk Zygalski, who invented it about October 1938. The bomby (at Bletchley Park, “bombe”) the Poles used were models of Enigma to solve the ciphers. The Poles did amazing work using no electrical devices. The British bombes were electro-mechanical.

With their sheets and bomby, and knowing from intercepts that their country was about to be invaded, the Poles were persuaded to share their information with the French and British. The British had decided to take a crack at Enigma codes, but it was too late; the Germans had added complications that made breaking it impossible. The Poles, having a ten year head start, were able to take advantage of the days when coding methods were simpler, and operators, becoming used to the new system, made some serious mistakes. On July 25, 1939, at a secret meeting in the Kabackie Woods near the town of Pyry, the Poles handed over their complete solution to the German codes, their Enigma replicas and bomby to the dumbfounded British.

Present at that meeting, were Denniston and Knox for the IS and Bertrand and Braquenie for the French. Each party did receive a complete 3 rotor Enigma and all drawings. On September 1, 1939 Hitler invaded Poland. On the 5th, the codebreakers packed up their Enigma replicas, Zygalski sheets and bomby, and made a run for France. After a mad flight in the company of thousands of others trying desperately to flee the Germans, they made it through Austria to France, but had to destroy all their equipment along the way except for two machines. A team of 15 Poles continued their work in France under the leadership of Captain Bertrand at the castle of Gretz located near Paris. They shared their work with the British. In fact, the British furnished them with sixty sets of 26 Zygalski sheets, since theirs had been destroyed in the evacuation.


After the invasion of France, all of Bertrand’s team moved to the “Zone Libre” free zone in south of France where they reorganized in a castle, PC-Cadix near the city of Uzes. Bertrand did return sometime later to Paris to collect the parts of Enigma machines that were manufactured in the suburbs of Paris. They were able to make four more machines. When the Germans occupied the rest of France (beginning 1942), the Polish codebreakers fled to England, but only some of them made it. Most were captured by the Germans while attempting to cross the Pyrenees into Spain. Since it was their brilliant work, turned over to the British, that allowed the Allies to read the German messages, it is hard to understand why the English never allowed them to work as codebreakers on the vital Kriegsmarine (Navy) Schlüssel-M traffic, which was not broken until naval rotors VI and VII were captured. It certainly seems that Rejewski would have been able to employ the same methods in solving the wiring of those rotors that he had so successfully used before. Apparently, the British decided to keep foreigners from working at Bletchley Park, although that changed, too, when the Americans got involved.

Was it British arrogance that denied the Poles their due in so many publications once “Ultra” was no longer under wraps? Perhaps not. The secrecy was so tight that most of the British codebreakers could not have known that their work was based on Polish success. And what of the three men who whose efforts helped to shorten World War II? Jerzy Rózycki was lost at sea Jan. 9, 1942, en route from Algeria to France. Henryk Zygalski decided to remain in England after the War, where he died in 1978. Marian Rejewski returned to Poland, where he died in 1980 at the age of 74. To add injury to insult, at the Yalta Conference in February 1945, the Communist Lublin Party in Poland was recognized, but not the Polish Government in exile in London.

These three men received little monetary compensation for their efforts, not much in the way of promotions, and only a few minor Polish decorations. They merited the highest accolades of all the Allied Nations. Perhaps their satisfaction came from a job well done.

Most of what we know about Enigma comes from British sources. Bertrand’s book gives a different slant on Enigma, and is a valuable resource.

Reviewed by George C. Constantinides[1]

This is one of the most important works yet published on the history of Allied cryptologic successes against Enigma. Despite its value, and perhaps because of certain doubts that existed about the author’s claims and the accuracy of his account, it has never been translated into English. That failure is now inexcusable in light of the latest evidence, which supports the author’s story. Bertrand was chief of the French cryptologic section in 1939-1940; his work in this sphere extended back into the 1930s. After the war, he served in the French service SDECE as deputy chief until 1950.

There are two segments. One is on Enigma and the cryptographic service’s work until 1942, partly under the German occupier’s nose; the other is on Bertrand’s resistance work, capture, and escape. Giving the Poles the main credit for the early successes against the Enigma machine, he also credits the aid provided by French intelligence, whose agent Asche was an employee of the German cryptographic service in the 1930s.

Ronald Lewin in Ultra Goes to War[2] describes Bertrand’s account of his career as overblown and quotes a leading French historian to the effect that Bertrand was boastful in this work. He also points out that all those associated with Bertrand—Poles, British, and French—agree that he made a genuine contribution, but none agree with his own large claims. More recently, Hinsley’s British Intelligence in the Second World War[3] contains an appendix on Enigma that appears to support many of Bertrand’s claims. The testimony of General Henri Navarre, who worked with Bertrand in the 1930s, is called to our attention by Calvocoressi in Top Secret Ultra[4]. Whatever the final verdict, he was still one of those few French officers who knew of the Allied cryptanalytical success and guarded it, no small input to victory in itself. David Kahn, in a review of Francis Winterbotham’ s work, accepts Bertrand’s version of how Enigma was broken.

[1] Constantinides, George C. (1983). Intelligence and Espionage: An Analytical Bibliography. Boulder, CO: Westview Press, pp. 81-82

[2] Lewin, Ronald (1978). Ultra Goes to War: The First Account of World War II’s Greatest Secret Based On Official Documents. London: Hutchinson

[3] Hinsley, F. H. (1990) and C. A. G. Simkins. British intelligence in the Second World War, Vol. 4, Security and Counterintelligence. London: HMSO

[4] Calvocoressi, Peter (1980, 2001). Top Secret Ultra. Kidderminster, England: M. & M. Baldwin


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2 Responses to Enigma

  1. Pingback: Breach of Security | Intelligence Analysis and Reporting

  2. Pingback: The Ultra Secret | Intelligence Analysis and Reporting

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