The Enigma Code Breach
By Jan Bury
2. Polish Pre-War
Code Breakers in the Early Period (1930s)
3. The Methods of Cipher Breach
4. Beginning of the W.W.II -
Evacuation to France
There have been numerous articles and books about the Enigma code breach. However, the
role that the Polish cryptologists' school had played in it has always been omitted. Such
an approach was spread since 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. It is very little known in the West, that the first to break the
Enigma-enciphered messages were the Poles and this happened in the 1930s.
There in also an absurd version spread by Mr. Winterbotham, who claims that the British
got an Enigma from Poles, who apparently had stolen a set from a German factory, thanks to
their mythical agent who was employed there.
My intention was to make a reliable approach for a reader in the West concerning the
greatest mystery of World War II. I decided to base on the published sources that are
available in Poland and are considered as official and reliable.
Polish 3 Rotor Enigma Machine
Polish Pre-War Code Breakers In The Early Period (1930s)
The first trials in Poland to break the newly introduced cipher by the Wehrmacht and
Kriegsmarine were in 1928. The messages that were encoded with a 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 fruitless. It seemed that the new cipher was a strong
cryptography and cannot be cracked in an easy way. 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 have started
working at the Ciphers Office. Later these students graduated a course of cryptography
prepared by the Office. The best were: Marian Rejewski, Jerzy Rozycki and Henryk Zygalski
who could work both at the University and at the General Staff's Ciphers Office without
any problems at that time.
In the autumn of 1930, a new branch of the Ciphers Office was
opened in utmost secrecy in Poznan. Rejewski, as well as his colleagues were employed
there. In 1932, the group was moved to Warsaw, to start working on the Enigma Cipher.
Their first success was a German Navy 4-letter cipher break. Rejewski was considered a
leading cryptologist within the group. He was looking forward the new way of breaking the
sophisticated German code. Since the Polish intelligence got an Enigma machine, Rejewski
could develop the scheme of encryption from the mathematical point of view. Unfortunately,
that machine was a commercial product, and the German army used the more complicated
Enigma with auxiliary connectors' plate at the front panel.
During 1931, Polish Intelligence co-operated with the French Deuxieme Bureau, which led
a most important agent within the Reichswehr Cipher's Office. Rejewski got a description
of the militarised Enigma, as well as old keys tables. This helped him to eliminate many
unknown figures in the permutation-alike equation he had previously created. Finally, in
December 1932, Rejewski reconstructed the Enigma's internal connections. In January, 1933,
the two other cryptologist became also 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
It is being estimated, that during the 6-year period of Polish reading of the Enigma
messages (between January, 1933 and September, 1939), about 100.000 transmissions were
deciphered. The most important concerned the remilitarization of the Rhine Province,
Anschluss of Austria and seizure of the Sudetenland, the last could be dangerous to
The fact that the Enigma cipher was cracked was kept in the utmost secrecy even within
the Polish General Staff's II Directorate. The officers got the messages signed with a
code-name "Wicher" (that was the Enigma code break) that were 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 have been
working there until the breakout of WW II on 1 September, 1939.
Although the French helped the Poles with the Enigma code break, the fact was in
exclusive hands of Poles until July 1939.
3. The Methods Of Cipher Breach
In February 1933, the Polish Army's General Staff placed an order at the AVA Radio
Workshops in Warsaw to build military Enigma doubles. During that time, the General Staff
possessed only one Enigma that was of a commercial type, without front panel auxiliary
connectors that made the cipher stronger. By mid-1934, about 15 "made in Poland"
Enigma's have been delivered. By the end of August 1939, about 70 such units were
On 15 September, 1938, just two weeks before the conference in Munich, the Germans
changed drastically their methods of using the Enigma cipher. Since the new key scheme
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 a machine
named "bomba kryptologiczna" (a cryptologic bomb), which was soon produced at
the AVA Workshops. Also a "cyclometer" machine helped to assess the pattern of
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). The method
allowed finding convergent places for the entire set.
However, starting with December 1938, the Germans upgraded their Enigma machines with 2
extra ciphering rotors (altogether 5 rotors). Although the Polish cryptographers could
still read the German messages, the mass decryption effort required using 60 instead of
only six cryptologic bombs and 60 paper sheets sets. During mid-July, 1939, Chief-of-Staff
Lt.-Gen. Waclaw Stachiewicz, authorised the Ciphers Office to share all their knowledge on
Enigma with the allied intelligence services. The representatives of France and England
got Polish-made clones of the Enigma encryption machine during the meeting in Warsaw
between 24 and 26 July, 1939. On 16 August 1939, General Stewart Menzies was given a copy
of Enigma at the Victoria Station in London. The British begun to read the Enigma messages
in mid-August, 1939.
4. Beginning Of The
W.W.II - Evacuation To France
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 got to France during the last days of September 1939.
In October 1939, a joint Polish-French radio intelligence centre in Gretz-Armainvillers
near Paris was created. It was given a code name "Bruno." Furthermore, the
"Bruno" centre had a Teletype link to Gov't Code and Ciphers School in England.
There were also Spanish code breakers employed at "Bruno" to crack the Spanish
and Italian ciphers.
3 Rotor Enigma Machine
Enigma Machine, Closed
Enigma Machine Plug Panel
Enigma Machine Rotors
Military Grade Enigma
Military Grade Enigma
Military Grade Enigma
An Early Enigma Model B
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" centre on 17 January 1940 was from 28 October 1939.
The most helpful messages to assess the routine of the German Army Signals Corps were
those sent every day just before 2400 hours. There was important information on call
signs, wavelengths, and hours of operation, etc.
Pre-war French Enigma clone
made thanks to the Polish Intelligence
Lacida – A Polish-made crypto machine
used in diplo communications.
Photo from 'Szyfr Enigmy - Metody Zlamania' book
An Enigma Machine
‘Cryptologic bomb’ machine (Bomba kryptologiczna) -
drawing from M.Rejewski’s papers
|There were also false messages to deceive the enemy ELINT/SIGINT efforts, sent by the
Germans. 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
On 10 June 1940, the "Bruno" unit got an order to evacuation. On 24 June 1940
the cryptologists were evacuated by three French Air Force aeroplanes to Algeria. 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, General Staff.
Enigma’s Ciphering Rotors
Enigma’s Ciphering Rotors
Drawing from M.Rejewski’s papers
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 in
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." The "Bruno"
centre successor decrypted the following types of German messages:
- German military orders to the units in Europe and in Libya,
- SS and Police (Polizei) messages from Europe,
- Spy radio communications between the field agents in Europe or in Libya and Abwehr HQ in
- Diplomatic communications and German Armistice Commission's
- Communications in Wiesbaden and their branches in France and in North Africa.
Italian Naval crypto officers operating an Enigma machine.
They do not know the cipher has been broken by Allied forces
Photocopy of M.Rejewski’s
Master of Philosophy diploma from
Poznan University dated 1 March 1929
Furthermore, the Fouzes "Cadix" unit got a branch in Algiers, led by a Polish
II Directorate's officer, Maj. (later Maj.-Gen.) M. Z. Rygor-Slowikowski. The unit was
located in the Kouba villa in Algiers' Kouba suburbs. 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 M/S "Lamoriciere"
he was travelling by, sunk near Balearic Isles.
Because of German ELINT threat, the unit's members were evacuated on 6 November 1942.
Rejewski and Zygalski managed to get to neutral Spain. Later, via Gibraltar, they were
transferred to England, where they started working at the Polish Army Signals Corps in
Boxmoor near London, in fact for the Polish Armed Forces Branch "300" of the II
Directorate. They later cracked the German SS formations cipher.
The ability to read the enemy's communications by the allied forces was very important
factor, which undoubtedly has contributed to the victory over the Nazi Germany. It was the
most important source on the Nazi Germany that the West had. Perhaps, the Soviets were
also given intelligence gathered in such a way.
Unfortunately, there is no evidence that the Poles made any worth use of the
intelligence they gathered from Enigma coded messages before 1939. Furthermore, the fact
that they possessed such a ability was known by the British. There is also an interesting
event, that the Enigma cipher's algorithm was considered strong, and was used in the Unix
OS encryption in the 1970s.
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
in: Applicaciones Mathematicae. 16, No. 4, Warsaw 1980.
5. Marian Rejewski: 'How Polish Mathematicians Deciphered the Enigma'; in: Annals of
the History of Computing. Arlington, Vol. 3, No. 3, July 1981.
Marian Rejewski – one of the brilliant
Polish code breakers
H. Zygalski enroute to Algeria
Maj. M.Z. Rygor-Slowikowski
being decorated by Gen. Jacob Devers
At Cadix. Mrs. Mary Bertrand
is in the foreground
Polish code breakers at Cadix
(L to R): Jan Gralinski,
and Piotr Smolenski.
They all died during the M/S
Lamoriciere’s accident in
Polish and Spanish code breakers at “Cadix”.
M.Rejewski (first from the left),
H.Zygalski (fourth from the left),
J.Rozycki (sixth from the left),
Eng. A.Palluth (eighth from the left)
Rejewski’s documents issued
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