Poles were instrumental in breaking the famous German Enigma code. Not too many people worldwide - even these interested in the history of World War II realize this. Solving Enigma codes was extremely important for the fate of the war, especially the Battle of Britain. But British mathematicians would probably not be able to know so much about German war machine and plans so quickly if not the work of Polish mathematicians in thirties. Poles were able to crack the initial code and the later more complicated versions, they even built the machines which allowed to search for all possible combinations in a couple of hours. Just before Poland was attacked starting War World II, some of these machines were given to French code breakers and some to British.
Polish intelligence was working on decoding German coded messages since the establishment of the Polish state after World War I, for some time Poles were able to read German naval signals. Germans code was significantly improved in 1930 after constructing military version of Enigma machines. For the first two years Poles were unable to crack the code. The real boost in understanding the code was made in 1932 when the group of cryptologists was enriched by three Polish mathematicians who graduated from Poznan (Posen) university after completing the cryptology course and knew German language very well - Marian Rejewski, Jerzy Rozycki and Henryk Zygalski.
Since military versions of Enigma machine were not available on the market, Poles had to build its own version relying on commercial versions. French (Bertrand) also helped Poles with a general idea of Enigma structure and principles. But even after knowing the principles of the Enigma and having the copy of the machine - the task of understanding the code seems to be impossible since there were hundreds of thousands ways to change the possible settings.
The situation was vastly improved after Rejewski invented so called "cyclometer" and Rozycki added "clock" to it. It enabled to set a catalogue of the possible settings and by comparison find out what were initial settings. Since June 1934 Poles were able to read German coded messages like these about a murder of hundreds of SA functionaries from SS and Gestapo in the Night of the Long Knives . Poles were able to read about 75% of the intercepted coded messages without too much trouble until 1938. During this time Germans were introduced some changes to their coding systems but Poles were able to crack it each time.
The real challenge came in 1938 when Germans introduced a new version of Enigma - on 15 September 1938, two weeks before the Munich conference. These changes created need for further automation of decryptment. Poles constructed another device, much more supreme to the cyclometer. They called it bomba in Polish meaning "splendid", "sensational" and also a name of delicious ice-cream dessert which was a very popular in Warsaw in this time. The electric system of revolving rotors generated over two hours 17,576 different combinations of codes. When the rotors aligned in the sought-for position the motor was stopping automatically and the proper indication could be read. This helped to read German coded messages again.
Since the war in Poland seems to be inevitable the tripartite meeting with the French and British cryptologists took place in Warsaw at the end of July 1939. Both, French and British were astounded by Polish "bombe". French and British were given Polish-made military model of Enigma and also technical drawings of 'bombe" and other devices invented by Poles. In the same time, after annexation of Austria also British showed more interest in intelligence contacts with their allies.
During the war Polish operations were suspended, with the help of Bertrand Polish decoders were able to pass through Romania to Algeria and later work in a full secrecy in a French castle, Chateau de Fouzes in South France - part of unoccupied France as a part of Cadix group. After Germans invaded the free zone all Poles (fifteen persons) had to escape. Some of them were caught by Nazis and dies in concentration or labor camps. Rejewski and Zygalski (Rozycki died in a ship accident returning from Algiers to France) were able to pass through Pyrenees to Spain were they were arrested and imprisoned in Merida.
Eventually Poles ended up in Great Britain but because of the mistrust they were not given any important tasks in British "Ultra" decoding operations. Unfortunately, Polish contribution to the solving Enigma secrets is not properly acknowledged in British and world documentary literature of Enigma, Poles were almost forgotten . This situation is improving recently when Prince Andrew presented a copy of the Enigma machine to Polish prime minister as a symbol of importance of the role played by Poles in the war.
This story as well as a history of British decoding of Enigma are described in a book written by Wladyslaw Kozaczuk and Jerzy Straszak called "Enigma, how the Poles broke the Nazi Code". Dr. Kozaczuk was able to work with Marian Rejewski who was one of the biggest contributors in solving Enigma code. Jerzy Straszak, as a former Polish naval intelligence officer in England, tells a story of Enigma in England.
It is written in an interesting way even for people who do not have any special interests in decoding operations since it refers to so many events which happened before and during the war. The information about some of these events was decipher by cryptologists. The book contains many illustrations, photographs of the enigma and other decoding devices and also a brief description of how deciphering and decoding really works.
It has some humor, not easy considering the seriousness of the situation. For instance it describes how Poles who were imprisoned in Spain were taking advantage of a complete ignorance of Polish language by Spanish guards - sending the information "decoded" in alleged names of the Polish prisoners.
The book is divided into two parts, the first devoted to Enigma's decoding history in Poland and the second describing the history of Enigma in Great Britain. The appendix contains biographical articles about some Enigma people as well as a history of French contribution and British literature about Polish contribution to solving Enigma. I truly recommend it!
Enigma: How the Poles Broke the Nazi Code (Polish Histories) by Wladyslaw Kozaczuk, Jerzy Straszak