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 Krygowski 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.

Select this link to view photos of key Polish code breakers.


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

Jan Bury SP5XZG
Warsaw, Poland
e-mail: (now unknown)

Back To the Enigma Page