The Enigma: The Secret Weapon of World War II

The Enigma—A Polish View by Jan Bury


The Enigma:
The Secret Weapon of World War II
Polish American Journal
October 1990

In the streets of the Chateau des Fouzes near Uzes, France, a two-story structure, code-named Poste de Commande CADIX, three Polish cryptologists were busy cracking the Nazis’ "unbreakable" Enigma code. By that day in September 1941, Marian Rejewski, Henryk Zygalkski and Jerzy Rozycki had successfully deciphered an intercepted top-secret message, after decoding the recently changed three-letter key.

A short-wave operator in the chateau’s basement transmitted the deciphered information to a relay station in the Mediterranean. It was picked up by British Field Marshal Bernard Montgomery’s desert headquarters. British tanks had launched a successful surprise attack on a desert base that Nazi General Erwin Rommel had intended to evacuate.

This tactic was one of thousands of offensive and defensive attacks that the Allies based on cryptogrammic information siphoned to them from the three Polish intellectuals. Knowing beforehand of Nazi plans saved thousands of lives in Normandy and North Africa and turned an immense September 1940 air raid on London from a potential disaster into a Royal Air Force victory.

Alerting Resistance fighters in Albania and Yugoslavia to Nazi troop movements, tracking Gestapo activities throughout France and putting Adolf Hitler’s orders to Rommel in Allied hands even before the Nazi general received them, were also major accomplishments of the perceptive cryptologists.

Rejewski, Zygalski and Rozycki started breaking the Enigma cipher when in Poznan, a rural college town in the Prussian section of pre-War Poland. They responded individually to the Polish government’s invitation to join a military cryptography course. The final exam was an actual German military communication expressed in the so-called "Double Dice" code that National Party (Nazi) foreign affairs expert Alfred Rosenberg had boasted was "insoluble." Rejewski, Zygalski and Rozycki, each acting on their own, broke the code. The Polish government promptly offered each of them a position unraveling intercepted German Navy and Air Force coded messages.

The Enigma itself resembled a tremendous typewriter. The keyboard activated three rotating drums, which contained the 26 letters of the alphabet. An electrical current running from one to the other and back created 100,391,791,500 variations.

In 1932, Rejewski discovered that the Nazi keyboard was wired to the entry drum, not in keyboard order, but in alphabetical order. After this incident, the trio began to construct a decoding machine that could translate Enigma’s messages automatically. From 1933 to 1939, the decoder called La Bomba, "The Bomb," so-named for its cylindrical appearance, traced Nazi naval, air and land movements for the Polish high command. Early in 1939, facing an oncoming invasion, the Polish government decided to share their Enigma translators with the French and British.

Living With Reality
Even with tracing Hitler’s troop operations, Poland still fell to invasion of the Nazis’ on Sept. 1, 1939. From the Cipher Center in Warsaw, the three Polish mathematicians took their machines and fled to Romania. They were then rushed across the border into Yugoslavia and then through Italy to Paris, by the orders of Bertrand. The trio joined a special international intelligence group called Unit Z, and by the end of October, they had broken the newest Enigma code variations and had designed an improved version of La Bomba.

The French high command refused to use the information that the Enigma translators provided, which could have aided them in the invasion of the Nazi troops into France through Belgium on May 10, 1940. However, the British did consider intercepted Enigma communications about Nazi Gen. Brauchitisch’s movements in time to evacuate their army at Dunkirk.

In late 1941, young Rozycki crossed the Mediterranean to Algiers to work with Enigma receptors that Unit Z had set up there. Returning through a driving rainstorm on Jan. 9, 1042, the passenger ship Lamoriciere struck an underwater object near the Balearic Islands and sank almost immediately. Rozycki and 221 other passengers, including two other Polish members of the cryptographic center, died in the accident, which might have been caused by an uncharted mine.

Nazi surveillance of Vichy, France was putting the CADIX center in great danger. A police raid on the farm adjoining the CADIX chateau provoked Unit Z to decide to evacuate. The cryptographers packed their equipment and left Nov. 9, the day after the Allies landed in North Africa. They were in isolation for two years in Vichy. The group had intercepted more than 9,000 secret dispatches, including many that led to defeats of Nazi units in Yugoslavia, Greece and Russia and countlessly aided the Allied commanders who planned the invasion of North Africa.

On Jan. 29, 1943, a French smuggler led the duo across the Pyrenees to escape from France. The next day the two were arrested by Spanish security police and confined in a series of prison camps until May. The two men concealed their true identities, even from other Polish refugees. After their release, they worked their way to Portugal and then to Gibraltar. From there the men were flown to England, where they were commissioned lieutenants in the Polish Army in Britain, set to work cracking SS codes.

Rejewski returned to Poland after the war. He was partially crippled by rheumatism that he had contracted in the prison camps in Spain. He held minor administrative posts at the university in Poznan until his retirement in 1967. He died in 1980 at the age of 75. Henryk Zygalski remained in England, where he taught at Battersea Technical College. He died in Plymouth in 1978.

Thanks to the Enigma codebreakers’ calculations and construction of La Bomba, which they developed and delivered to the Allies, the British were able to intercept reports from Rommel in North Africa, locate and sink the battleship Bismarck, find and destroy the V-1 and V-2 production center at Peenemunde and select the least-defended beaches for the Normandy invasion.

Digested from The Retired Officer

Top of page

The Enigma: A Polish View
The Greatest Secret of World War II—The Enigma Code Breach
by Jan Bury

1. Foreword
2. Polish pre-war code breakers (1930's).
3. The methods of breaching the cipher.
4. Beginning of WWII - Evacuation to France.
5. Enigma in WW II - speculation.
6. Conclusions.
7. Bibliography.

There have been numerous articles and books written about the Enigma code breach. However, the role that the Polish cryptologist's school had played in it has always been omitted. An example of this was seen in 1974, when F. W. Winterbotham published a book titled "The Ultra Secret", where he claimed that the British were the first to break this cipher. There has been very little published about the people who were truly the first to break the Enigma enciphered messages. This distinction belongs to the Poles who accomplished that feat in the late 1930s.

There in also another example in Mr. Winterbotham book, which claims that the British got an Enigma from the Poles, who apparently had stolen a machine from a German factory, thanks a mythical agent who was employed there. My intention is to set the facts straight for a subject which was one of the greatest secrets of World War II. I decided to base this account on published sources that are available in Poland and are considered to be official and reliable.

In Poland, the first attempts to break the newly introduced Wehrmacht and Kriegsmarine cipher were made in 1928. The messages that were encoded with the new cipher were being picked up by four Polish ELINT stations: in Warsaw, Starogard near Gdansk (or then Danzig), in Poznan and in Krzeslawice near Cracow. Unfortunately, the methods involved in breaking the cipher code were ineffective and fruitless. Quickly, it was realized that the new cipher would not be broken easily. Therefore, the Ciphers Office (BS) of the Polish Army's General Staff decided to ask mathematicians for help. In January 1929, the Dean of the Department of Mathematics, Professor Zdzislaw Kryglowski from the University of Poznan, made a list of his best graduating students who could begin working at the Ciphers Office. Later, these students graduated from a cryptography course prepared by that Office. The best graduates were: Marian Rejewski, Jerzy Rozycki and Henryk Zygalski who could work simultaneously at the University and at the General Staff's Ciphers Office without any problems.

In the autumn of 1930, a new branch of the Ciphers Office opened in utmost secrecy in Poznan. Rejewski, as well as his colleagues were immediately employed there. In 1932, the group was moved to Warsaw, to start working on the Enigma Cipher. Their first success was decoding a German Navy four letter cipher. Rejewski was considered a leading cryptologist within the group. He was looking forward to a new way of breaking the sophisticated German code. Since Polish intelligence had an Enigma machine, Rejewski could develop a scheme of decryption from a mathematical viewpoint. Unfortunately, that machine was a commercial product, and the German army used the more complicated Enigma with an auxiliary connectors plate at the front panel which greatly multiplied the possible number of permutations.

During 1931, Polish Intelligence co-operated with the French Deuxieme Bureau. This co-operation eventually led to an important agent within the Reichswehr Cipher's Office. Rejewski was able to obtain a description of the militarized version of the Enigma, as well as old key tables. This helped him to eliminate many unknown variables in the "permutation-like" equation he had previously created. Finally, in December 1932, Rejewski reconstructed the Enigma's internal connections. In January, 1933, two other cryptologists also became involved in Rejewski's work. In the same month, the first German messages were decrypted. Since then, the General Staff had access to the most secret data transmitted by the German Army, Navy, Air Force, as well as the Ministry of Foreign Affairs.

It is estimated that during a six year period between January 1933 and September 1939, the Poles were able to decipher about 100,000 transmissions . The most important concerned the remilitarization of the Rhein Province, Anschluss of Austria and seizure of the Sudetenland. The last could be dangerous to Poland's interests. The fact that the Enigma cipher was cracked was kept in the utmost secrecy even within the Polish General Staff's II Directorate. Officers received decoded messages signed with a code-name "Wicher" (that was the Enigma code break) that was considered fully reliable, but the source was classified.

In 1934, the General Staff's Cipher Office established a new site for their German branch (BS-4) in the Kabaty Forest near Warsaw. Rejewski and his colleagues worked there until the breakout of WW II on 1 September, 1939. Although the French helped the Poles with the Enigma code break, all material was in the exclusive hands of Poles until July 1939.


In February 1933, the Polish Army's General Staff placed an order at the AVA Radio Workshops in Warsaw to build copies of the military Enigma. During that time, the General Staff possessed only one Enigma which was a commercial type and lacked the front panel auxiliary connectors that made the cipher stronger. By mid-1934, about fifteen "made in Poland" Enigma's had been delivered. By the end of August 1939, about seventy such units were produced.

On 15 September, 1938, just two weeks before the conference in Munich, the Germans drastically changed their methods of using the Enigma cipher. Since the new key seemed to be more complicated, the Polish cryptologists invented the first mechanical pseudo-computers to help them in their work. In October 1938, Rejewski designed the machine named "bomba kryptologiczna" (cryptologic bomb), which was soon produced at the AVA Workshops. Also a "cyclometer" machine helped to assess the pattern of the key. Simultaneously, the new method of a double-key crack was invented, which consisted of using sheets of paper with 51 by 51 holes (each set consisted of 26 sheets). This method allowed the finding of convergent places for the entire set.

However, starting in December 1938, the Germans upgraded their Enigma
machines with two extra ciphering rotors (5 rotors altogether). Although the Polish cryptographers could still read the German messages, the mass decryption effort now required sixty 60 instead of only six cryptologic bombs and sixty paper sheet sets. During mid-July 1939, Chief-of-Staff Lt.-Gen. Waclaw Stachiewicz, authorized the Ciphers Office to share all their knowledge on Enigma with the Allied intelligence services. The Allied representatives in France and England received Polish-made clones of the Enigma encryption machine during the a meeting in Warsaw between 24 and 26 July, 1939. On 16 August 1939, General Stewart Menzies was given a copy of an Enigma at the Victoria Station in London. The British began to read Enigma messages in mid-August, 1939.

On 1 September 1939, Nazi Germany invaded Poland. The Ciphers Office, as well as ELINT surveillance stations were evacuated to Romania. While the situation on the front deteriorated, and the Soviet Union invaded Poland on 17 September 1939, the Ciphers Office received an order to destroy all documentation and equipment. Rejewski, Zygalski and Rozycki esacaped to France during the last days of September 1939. In October 1939, a joint Polish-French radiointelligence center in Gretz-Armainvillers near Paris was created. It was given the code name "Bruno". Furthermore, the Bruno center had a Teletype link to the Gov't Code and Ciphers School in England. There were also Spanish codebreakers employed at Bruno to crack the Spanish and Italian ciphers.

The main problem the cryptologists were facing was the exchange of the key system, which took place in the German Army on 1 July 1939. The first decrypted message at the Bruno center on 17 January 1940 was from a message sent on 28 October 1939. The most helpful messages to assess the routine of the German Army Signals Corps were those sent every day just prior to 2400 hours. Important information such as call signs, wavelengths, and hours of operation were obtained. Germans also sent false messages to deceive the enemy ELINT/SIGINT efforts. However, the most characteristic messages were: situation reports sent in the morning, noon, afternoons, evenings; intelligence reports; orders; logistic reports and others.

The unit's most important effort was the warning about the German preparation to attack France. On 10 June 1940, the Bruno unit received an evacuation order. On 24 June 1940, the cryptologists were evacuated by three French Air Force airplanes to Algeria and in mid-July 1940, the unit started to work clandestinely in Algiers. The Poles were enrolled into the Polish Armed Forces Branch "300" of the II Directorate. The Polish cryptologists were however to come back soon to occupied France under a secret agreement between the Polish and Free French governments and continue their work underground in the City of Fouzes near Nimes. In the beginning of October 1940, the new secret unit was formed in Fouzes and code-named "Cadix". Cadix succeeded the Bruno center and decrypted the following types of German messages:

- German military orders to the units in Europe and Libya.
- SS and Police (Polizei) messages from Europe.
- Spy radio communications between field agents in Europe or in
 Libya and Abwehr HQ in Stuttgart.
- Diplomatic communications and German Armistice
 Commission communications in Wiesbaden and their branches
 in France and in North Africa.

Furthermore, the Fouzes Cadix unit opened a branch in Algiers and was led by Polish II Directorate's officer, Maj. (later Maj.-Gen.) M. Z. Rygor-Slowikowski. The unit was located in the Kouba Villa, an Algiers suburb. Most of the intelligence gathered by his unit were used in preparation of the "Torch" Allied operation (North Africa Landing). Note that the Kouba (a.k.a. PO-1 branch) unit encrypted their messages using a Polish-made LCD (a.k.a. "Lacida") enciphering machine, which consisted
of a modified Remington typewriter combined with enciphering rotors.

Unfortunately, on 9 January 1942, Jerzy Rozycki died when the M/S "Lamoriciere" he was traveling in, sunk near the Balearic Isles. Because of German ELINT threat, the unit's members were evacuated on 6 November 1942. Rejewski and Zygalski managed to escape to neutral Spain. Later, via Gibraltar, they were transferred to England, where they started working in the Polish Army Signals Corps in Boxmoor near London (Polish Armed Forces Branch "300" of the II Directorate). They later cracked the German SS formations cipher.

It has been suspected that since 1939, British intelligence was able to decrypt Enigma messages. There was a Soviet GRU intelligence network in Switzerland during WW II, led by a Hungarian geographer, Professor Sandor Rado. The group was pinpointed by the German ELINT and was given the code name "Die Rote Drei" (The Red Three). Rado's most important agent was Rudolf Roessler (code name "Lucy"). The information he provided was always very reliable, true and exact, however he has never told anyone who his agents were. He only mentioned, that he got the reports from: "Werther" from OKWehrmacht (German Army HQ), "Teddy" from OKHeer (Land Forces HQ), "Stefan" and "Ferdinand" from OKLuftwaffe (Air Force HQ) and "Olga" from the Reich's Ministry of Foreign Affairs. One hypothesis claims that these personalities had never existed and that R. Roessler gathered intelligence from Enigma code breaking or he was supported by the British via another agent within Rado's network, Allan Alexander Foote ("Jim"). Perhaps the British acted as Stalin's supporters to encourage him to finish the war with the lesser effort from the Western side, especially considering the Eastern Europe liberation.

The ability by the Allies to read the enemy's communications was a very important factor in the war effort and undoubtedly contributed to the victory over Nazi Germany. Perhaps, the Soviets were also given some of the intelligence gathered from Enigma message decipherment. The Enigma code was considered so strong that it's algorithm was incorporated into the Unix Operating System developed in the late 1960's.

1. Krzysztof Gaj: Szyfr Enigmy. Metody Zlamania [Enigma Cipher. The methods of Breaking], WKL, Warsaw 1989.
2. Wladyslaw Kozaczuk: W kregu Enigmy [In the Enigma Circle], KiW, Warsaw 1986.
3. Andrzej Peplonski: Wywiad Polskich Sil Zbrojnych na Zachodzie 1939-1945 [Polish Armed Forces' Intelligence in the West 1939-1945], AWM, Warsaw 1995.
4. Marian Rejewski: 'An Application of the Theory of Permutations in Breaking the Enigma Cipher'; in: Applicaciones Mathematicae. 16, No. 4, Warsaw 1980.
5. Marian Rejewski: 'How Polish Mathematicians Deciphered the Enigma'. From Annals of the History of Computing. Arlington, Vol. 3, No. 3, July 1981.

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