The Allies were primarily successful at code breaking during World War II, although the Germans had some succeses of their own. This may have been because the Allies at the beginning of the War had a greater need for information on Axis intentions and than gave code breaking a greater priority. This may have been a more important factor than actual capabilities. The British had an active prgram to crack foreign codes, including the Italians, Japanese, and Spanish. The primary effort of course was directed at NAZI Germany. Histrorians for many years after the Warv did not know just how much the Allies were able to learn about Germany militaty activities by cracking the Wehrmacht Enigma Machine which the Germans were sure could not be cracked. As far as we know, the Japanese had no success at cracking American and British codes except for some lower level codes. The British were working on codes during the inter-War era, but beginning in 1939 mobilized a greatly expanded effort to crack the Enigma codes. The code name for the British effort to break into the the German military Enigma cipher machines was called Ultra. It was one of the most closely guarded secrets of the War. It was primarily conducted at a country estate known as Blechley Park. Some of the most capable and creative mathematicians in Britain were assigned the enormously difficult task of penetrating German military communications. Cracking Enigma was not a single task. Each of the three German services (Heer, Kriegsmarine, and Luftwaffe) had Enigma machines with different codes to crack. The naval Enigma machines proved a particularly difficult challenge. And the Germans gave the Italians Enigma machines. In addition there were other German codes. British cryptanalysts, led by Alan Turing, not only had an impact on the course of the War but in the process created the first true computer that would so change the modern world.
The Allies were primarily successful at code breaking during World War II, although the Germans had some succeses of their own. This may have been because the Allies at the beginning of the War had a greater need for information on Axis intentions and than gave code breaking a greater priority. This may have been a more important factor than actual capabilities. The British had an active prgram to crack foreign codes, including the Italians, Japanese, and Spanish. The primary effort of course was directed at NAZI Germany. Histrorians for many years after the Warv did not know just how much the Allies were able to learn about Germany militaty activities by cracking the Wehrmacht Enigma Machine which the Germans were sure could not be cracked. As far as we know, the Japanese had no success at cracking American and British codes except for some lower level codes.
The British during World War I did not have a centralized code breaking eeffort. The Army and Royal Navy had their own separate signals intelligence agencies. The Army unit was MI1b. The Royal Navy unit was NID25 (Room 40). The Russians obtained a major intelligence prize early in the War. They found a code book on the the German cruiser Magdeburg which had run aground in the Baltic. The Russians turned it over to the British. This gave the British insights into German secure communications for most of the War. Naval intelligence during the War, however, was primarily assessing the direction and volume of transmissions. One of the most important examples of code breaking was the British decryption of the Zimmerman Telegran, a factor in bringing America into the War. The American public was outraged. When Germany resumed unrestricted submarime warfare, there waslittle opposition to entering the War.
The British Government created the Code and Cypher School (GC&CS) in the aftermath of World War I (November 1919).
The British after the War made many adjustments as the wound down the massive military effort. Officials burdened with a massive War bebt looked at how various war time operations could be cutback to reduce costs. The Cabinet's Secret Service Committee, chaired by Lord Curzon, recommended that a single, centralized peace-time codebreaking agency should replace the separate service cryptology units. The Director of Naval Intelligence, Hugh Sinclair was assigned the task of leading the new GC&CS. Sinclair merged the staff of the war time Naval NID25 and Army MI1b units to create the new organization. It was a relatively small organization, about 25–30 officers and a comparablr number of clerical support staff. Victor Forbes in the Foreign Office chose the name to desguise the agency's purpose. GC&CS was ininitally assigned to the Admiralty in facilities at Watergate House, Adelphi, London. The function for public consumption was to "to advise as to the security of codes and cyphers used by all Government departments and to assist in their provision." Ther was a secret directive to "study the methods of cypher communications used by foreign powers." In the new peacetime enviroment, GC&CS focused primarily on diplomatic traffic. As a result, at the suggestion of Lord Curzon, the agency was transferred tobthe Foreign Office (1922).
The British were working on codes during the inter-War era. They easily brole the American an French diplomatic codes because they were so simplistic. With the Germans largely disarmed, there was not a lot of military traffic to work on. They broke the Italian naval codes. The Italians made it easy, encoding long political editorials from daily newspapers (1920s). The British broke simple Soviet codes and used them to publicize the fact tht the Soviets controlled and funded a number of left-wing domestic groups. As a result, the Soviets adopted a single use system that proved difficult to break. Japanese naval messages were beyond the reach of British reception stations. The British broke fairly simple diplomatic and attche codes. This access ended after American codebreaket H.O. Yardley sold the secrets as to how their codes were broken. As a result the Japanese adopted a more sophisticated machine cypher system. An intercept system was estblished in Hong Kong (1930s) and work began on the Japanese codes. Their real interested was, however, the Germans who also a few years earlier also adopted a cypher machine--Enigma. British code breakers began releasing information about their world war I successes. The Germans undertandably saw the need for a much more sophisticated code system. Enigma was much more complicated than the Japanese machines. They worked on Enigma and made some basic conclusions. They did not launch a major effort, even after Hitler began to rearm the country.
The British made some preliminary assessments avout Enigma, but were baffled by it. And thus did not launch a major effort. As a result of this and inconsulation with the French, GC&CS began to think as dod the Whermacht that cipher machines like Enigma were unbreakable. The British also broke Spanish codes an d read them during the Civil War. .
Britain and France almost went to War to defend Czechoslovakia (1938). Ware was prevented at the Munich Conferemce (September 1938). Primeminister Chamberlian thought he had achieved 'peace in our time". It soon becane evident that he had not. And with the German invasion of Czechoslovakia in total violation of the Munich Agreements, it soon became evident that war was inevitable (March 1939). The British thus mobilized a greatly expanded code breaking effort.
While the British made no real effort to crack the German Enigma Machine, the Poles working on their own, with very limited resources, not only worked on it, but actually cracked it. The Poles began their effort just vbefore the NAZIs seized power in Germany with a commercial Enigma (1932). They were aided by French intelligence which was able to get material from a German traitor. And as a neighboring country, they had aealth of intercepted messages on which to work. The Poles amazingly broke Enigma in just a few weeks built an Enigma machine and for several years were able gto read many German military communications. In the months leading up to the War, however, the Germans introduced further complications which left the Poles in the dark. The Poles did not share their achievement with the French or British. As a result of the Munich Crisis (September 1938), the Germans began introducing new complications to improve security. The Poles made some progress in getting back in, but futher German steps effectrively froze them out. The Poles did not have the resources to attack the complications posed by the German security measures. The German seizure of Czechoslovakia (March 1939) changed everything. The British began actively searching for allies for what was now an inevitable war with the Germans. They hoped to sign an agreement with the Soviet Union, but this proved elusive. They did sign an greenent with the Poles who realized that they were the next NAZI target. The British pledged with the support of France to guarantee Polish independence (March 31, 1939). Two days after the NAZI-Soviet Non-Agression Pact was signed, the Anglo-Polish Military Alliance was signed (August 25, 1939). As a result, a few days before the Germans struck, the Poles turned over to the British and French copies of their research material and the military Enigma they had built. These materials proved invaluable. Without them the British would have had to begun their efforts to crack Enigma virtually from scratch.
The British effort was primarily conducted at a country estate named known as Blechley Park located in the Buckinghamshire countryside. The Code and Cipher School did not have room for a greatly expanded operation. Thus the Government purchased the Bletchely Park estate for a greatly expanded effort. And the location in the countryside provided for a greater degree of security. The Polish acoomplishments were crucial in the cracking of Enigma. It gave the British the way into Enigma and the start they needed. The Polish system would, however, never worked over the long run. It was too time consuming and German upgrades made it more difficult to use. Many people made important contributions t Blethely Park. It was, howver, Alan Turing a young mathemetician that made the difference. British cryptanalysts, led by Turing, used innovative mathematical analysis. His unconventionl, brilliant insights cracked Enigma wide open. They had nothing to with the traditional methods of code breaking. Perhaps no other single individual played a more important role in the Allied war effort. Turing not only devloped important mathematical insights, but he turned features of Enigma against the Germans. As the operations at Bletchely Park expanded, the various sections began to establish themselves in pre-fabricated wooden huts set built on the expansive lawns of the Park. Each section was known by the hut numbers. Some of the most capable and creative mathematicians in Britain were assigned the enormously difficult task of penetrating German military communications. Some 12,000 men and women would work tirelessly at this facility throughout the War to break into Geman military communications. They created computing machines that were in effect the first computers. Gordon Welchman developed the electro-mechanical Bombe.
Tommy Flowers developed the electronic Colossus.
The code name for the British effort to break into the the foreign codes was Ultra. It is most often associated with the cracking of the Wehrmacht Enigma Machine. Cracking Enigma was not a single task. Each of the three German services (Heer, Kriegsmarine, and Luftwaffe) had Enigma machines with different codes to crack. The naval Enigma machines proved a particularly difficult challenge. And the Germans gave the Italians Enigma machines. In addition there were other German codes. Ultra is commonly associated with the Enima machine because the Germans were the greatest military threart. Ultra involved, however, not only Enigma, but other German codes as well as the codes of German allies. The British Ultra operated was primarily conducted at Bletchly Park where Alan Turing played a key role in achieving wht some of the v=best minds in Germny an Britain beliec=ved could not be dine. There was more to Ultra, howwever, than Bletchley Park no matter how critical the operatiin there was. The Bletchley code breakers wre aided y were aided by the bravery of both agents and ordinary seamen who risked all to capture needed codebooks and manuals. [Sebag-Montefiore]
Ultra was one of the most closely guarded secrets of the War. One effort to hide the fact that Enigma had been broken was to give the reports the the appearance of information developed through espionage by an M16 spy, code named Boniface who operated a network within the Reich. This was of course a total fabrication. Only the highest level commanders were told of the Ultra secret. As a result, in the early phase of the War, many commanders did not trust the Ultra inteligence reports. The British when acting on Ultra intercepts attempted to provide other plauasable reasons for the actiion. Thus when obtaining details on Italian convoys to supply the Afrika Korps they would not attack the convoy until first spotting it with air or naval reconsisance craft. Thus the Germans were not led to the conclusion that their Enigma mschines had been compromised. Thus major commanders like Rommel were convinced even late in the War that Enigma transmissions were secure. The most skeptical German coimmnder was Admiral Dönitz. There were just to many conincides of Allied units showing up at just the rightvtime and place in the vast Atlantic. He ordered intelligence assessments, but they all assured him that Enigma transmissions were secure. Even so, he orderd a fourth rotor for the naval Enigma. One factor operating for the Allies was that so mny U-bots were lost leaving lu\ittle information for OKM to assess. In this regard, the British Admiralty were concerned about how aggrssively the U.S. Navy after entering the war used the Ultra inteligence, concerned that it would compromose the secret.
Several norable individuals worked at Blechy Park. Oliver Strachey who had worked on codes during World War I was a early team leader. Strachley headed the section deciphering various messages on the Abwehr network which used turned German agents--the Double Cross system. Interestingly while mathematics was important, nost of the code breakers were not mathematicians. One of the mathematicans, was the brilliant theorist, Alan Turing. His prep school teacher wasn't impressed with his math skills and his ink-blotched copy book drove him to distraction. Alan as a schoolboy was often as ink blothed as his copy book.
To crack Enigma and other German messages, the British first needed mesages to work with. These wre provided by the 'Y' Service. This was a chain of wireless intercept stations located throughout Britain. There were also sites in countries overseas. Royal Navy ships at sea also intercepted messages. The Y Service consisted of thousands of wireless operators, consisting of many civilians, including Wrens, WAAF personnel and members of the ATS. They tracked German and other enemy transmissions all over the frequency dial. They carefully logged every letter or figure. These messages were then forwarded to Station X--Bletchely Park. Here they were not only decoded, but fitted together like a gigantic jigsaw puzzle to create a composite view of enemy operations and intentions.
The British broke the German Enigma and Lorenz ciphers. The code name for the British effort to crack the German military Enigma cipher machines was called Ultra. It was one of the most closely guarded secrets of the War. It was conducted at a country estate called Blechley Park. With the help of the Poles the British began working on the Enigma code machines that the German military used for radio communications. Effctive German communications were part of the reason for the victories in Poland and France. The French General Staff for example was using messengers to communications. While effective, the use of messages sent by radio meant that German military communications were vulnerable. The German relying on their preceived notions of supperiority were convinced that their Enigma cipher machine could not be ceacked. The Germans did not know of the Allied success until well after the War. British code breakers at Bletchley Park faced different problems with the Wehrmacht, Luftwaffe, and Kriegsmarina code. The Luftwaffe code proved the easiest to crack, primarily because flushed with sucess, the Luftwaffe was careless about following established security procedures. Many messages were read because operators did not follow procedures. The British suceeded in dechipering some Luftwaffe messages (May 1940), although regular and timely decoding was not possible until the end of the year. (We have noted different assessments as to how useful Ultra was during the Battle of Britain.) Working with uncoded German radio messages also provided valuable information. This provided valuable intercepts with infornmation on force strength and targetting was available to the RAF. Dechipering Naval messages proved more challenging. The Kriegsmarina Enigma msachines were also cracked, but was more difficult because their operators were more careful to follow procedures and a fourth rotar was eventually added. The Royal Navy managed to obtain an intact Enigma machine and associated material needed to set the machines. Cracking the Kriegsmarina Enigma msachines played a major role in the defeat of the U-boat campaign in the North Atlantic.
The British had also broke the Italian codes and ciphers before the War. When the Italians entered the war and began fighting with the Germans in North Africa and the Soviet Union, the Germans supplied them Enigma machines. The British had already to varying degrees cracked Enigma. The Italiam traffic proved relatively easy to crack because the Italians wee not very careful about security measures. And the information revealed proved vital in intercepting Italian convoys carying supplies to the Afrika Korps.
General John de Chastelain's American mother, Marion de Chastelain, helped run a spy ring targetting Vichy France. De Chastelain is best remembered for his role in IRA arms decommissioning. She worked for Sir William Stephenson, the Canadian running a spy ring for Britain in New York before and to a lesser extent after America entered the War. Stephenson over saw the British Security Co-ordination operation in Rockefeller Center. Elizbeth Thorpe was an American debutant who married a British diplomat. She was active in Warsaw before the War. She was very inteligent and bored. She found getting information out of diplomts a diverting activity. MI-5 incouraed her to do more. Accounts suggest she got information on Enigma. [Stevenson] There is little evidence of this. When she returned to Washington with her husbnd. De Chastelain became Thorpe's (code named Cynthia) handler. Thorpe developed a relationship with the press attaché in
Vichy France's Washington Embassy--Charles Brousse. Once a week, often more, de Chastelain would fly to Washington, take a taxi to the city center, and walk the last two blocks to the hotel where they met, entering through a side door. Cynthia, a shapely socialite, was caught un in the excitement. She would produce a package which Marion brought back to New York. It included the press attaché's notes of briefings, conversations and telegrams. She translated them and and returned the same day before they were missed by the attsché from the embassy safe. The intentions of the French fleet with powerful surfce units as wellnas submarines was of critical importance. Finally Cynthia went for the Vichy naval code books kept in a safe in the Vichy Washington Embassy. The material meant that the Briitish were able to read almost all French naval traffic. [Stevenson] Code books change, but possession of the material from the Vichy Embassy, helped Bletchely Park lay Vichy codes wide open. The Allies were able to monitor traffic between a French admiral on Martinique and French navy ships. Thus the Allies were rading French naval codes in the critical periid before the Torch landings (November 1942). The Torch landings werre opposed by Vichy firces and thus familiarity with naval planning saved British and American lives,
The British had cracked Spanish codes in the 1930s and because the Germans did not supply Enigmas to the Spanish, the British read Spanish messages througout the War.
The Brutish also broke the Japanese codes and ciphers. Bletchely Park like the Americans monitored the Japanese preparations for war. They did not pick up information on the Pearl Harbor attack, but they leaned a great deal about the Japanese. And even before Pearl Harbor there was copperation between American and British code breakers. [Smith, The Emperor's.] Code breakers on Ceylon cooperated. The Hong Kong unit moved to Singapore which was seen as more secure. Another unit was added in Australia. The British focus was on the German Enigma, but the British effort assisted in the Amerivan success.
Cryptology especially the breaking of enemy codes are the most closely guarded secrets of any country. The United States and Britain began to cooperate on code breaking even before America entered the War. Early cooperation was primarily on Japanese codes as American forces were not deployed in Europe. While the copperation began at an early stage, the sensitivity of the effort ensured that these early efforts were not easy. The cryptology units in both countries were suspicions of each other, especially their ability to keep secrets. [Budiansky] the British were still deeply distrustful because of the Y.O. Yardley affair. Yardley published a book about American code breaking which included information about British code breaking. The iniative, however, toi cooperate was made by the British. The pressing need for American assistabnce was the motivating factor. Primeminister Chamberlain had been dismissive of the Americans before the War, convinced that he could prevent a War. Even after the War began, he was not inclined to embrace the Americans and did not have a good relationship with President Roosevelt. This changed with the appointment of Winston Churchill as primeminister (May 10, 1940). He had since his appointment to the Admiralty (September 1939) been corresponding secretly with the President.
Churchill was anxious to secure American assistance hoping eventually for American entry into the War. He did not have a great deal to offer the Americans, especially as Britain was rapidly going bankrupt. One thing he could offer the Americans was advanced military and scientific technology that could assist America in its rearming effort. And a colalary concern was security. British Abassador Lord Lothian wrote President Roosevelt suggesting an exchange of information (July). "Should you approve the exchange of information, it has been suggested by my Government that, in order to avoid any risk of the information reaching our enemy, a small secret British mission consisting of two or three Service officers and civilian scientists should be dispatched immediately to this country to enter into discussions with Army and Navy experts ... His Majesty's Government would greatly appreciate it if the United States Government, having been given the full details of any British equipment or devices, would reciprocate by discussing certain secret information of a technical nature, which our technical experts are anxious to have, urgently." President Roosevelt and Primeminister Churchill shared a fascination with secret operations. Mrs. Roosevelt saw it when they later got together in the White House as a kind of Boys' Qwn mentaility. The President was immediately attracted to the idea. He even dismissed the objections of General Marshall and other senior commanders. This showed the level of his commitment to cooperation because General Marshall was probably the individual among all otghers that he relied on for militaey advise. A British team led by Sir Henry Tizard, a British senior scientific adviser, arrived in America (late-August 1940). He met with American officials and brought with him a range of advanced military technology--radar technology was among the items. The 'Tizard Mission' was the beginning of the two-way exchanges that would play a vital role in the Allied victory. This should be compared to the reluctant Axis cooperation. What Tizzard did not bring was the Ultra secret. Churchill did not think the Americans including the President had a "need to know" and was very concerned about maintaining the Ultra secret. Soon after, Churchill learned that the U.S. Army SIS had cracked the Japanese Purple cipher machine. With the Americans produced a Purple analoge machines able to read diplomatic transmissions in real time(October 1940). He probably also learned that the Americans were also working on the JN-25 naval codes. This made the prospect of cooperating with the Americans much more enticing because of the increasing Japanse agreesivenes and the signing of the Axis alliance. British cryptologists were also working on Japanese codes. Top secret discussions followed quickly leading to an agreement (November 1940). The two countries agreed to provide for "a full exchange of cryptographic systems, cryptoanalytical techniques, direction finding, radio interception, and other technical communication matters pertaining to the diplomatic, military, naval, and air services of Germany, Japan, and Italy."
The information designed by the Bletchley Park teams not only had an impact on the course of the War but in the process created the first true computer that would so change the modern world. The Allies surely would have won the War without Ultra. Although victory in the North Atlantic over the U-boats would have been much more difficult without Ultra. Ultra as a result helped shortened the war, thereby saving countless lives. It is not possible to assess the impact of the British codebreaking in isolation. The secret November 1940 agreement with the Americans meant that it was a joint Anglo-American effort. The Americans led with the Japanese codes, it is difficult to see, however, just how the Americans would have cracked into the Enigma traffic without the ground breaking work by the Poles and British. They may have managed, but it is not altogether certain and if they could have it would have been much later in the war. The Americans and Arlington Hall did, however, play a major role in breaking the Herman Lorenzode. As a result, the impact has to be seen as a combined Allied effort and it is difficult to assess the impact of the British American efforts separately. Most of the major benefits flowing from Ultra and Magic occurred sfter America entered the War.
A British reader writes, "HBC has provided a useful conmcise account Well done. The Queen is today dedicating a memorial at Bletchley Park to the memory of the staff that worked there. They now undertake to receive Guided Tours there. I went a few years back. I was amazed at the primirtive conditions that the staff had to work, and were told that what when on in their Hut was not to be revealed to other members of staff, such was the secrecy of the operation. I had a friend who I met through Rotary who had worked there , and he gave us a fascinating lecture about how the staff were recruited. He was a Professor of Mathemetics at Glasgow. After the War he taught Radio-Astronomy at Penn State,
returned to Canterbury in his retirement years to set up a Radio-Astronomy Department at the new (1964) University of Kent at Canterbury. A sad side to the story is that of Alan Turing, one of the most brilliant cryptographers. He committed suicide because he was a homosexual, which wa a criminal offence in those days." [July 15, 2011]
Budiansky, Stephen. "The Difficult Beginnings of US-British Codebreaking Cooperation." Intelligence and National Security Vo;. 15, no. 2 (Summer 2000), pp. 49-73.
Bury. Jan. "The Greatest Secret of World War II - The Enigma Code Breach".
Sebag-Montefiore, Hugh. Enigma: The Nattle for Code.
Smith, Michael. Station X: The Code Breakers of Bletchley Park.
Smith, Michael. The Emperor"s Codes: Bletchley Park and the Breaking of Japan's Secret Cyphers.
Stevenson, William. A Man Called Intrepid: The Secret War (New York, Harcourt Brace Jovanovich, 1976).
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