*** war and social upheaval: World War II -- country code

World War II: Country Code Breaking Efforts

World War II code breaking
Figure 1.--Operation Barbarossa launched the War in the East where World War II would be won or lost. Here a German supply train rumbeles east. Amazingly, Stalin had ample warnings of the NAZI invasion. His very effective intelligence servives informed him even though he orderd them to stop submitting such reports. (Some agents out of patriotism continued to so and would disappear into the Gulag.) Both the British and Americans with Ultra and Magic decrypts also infornmed him. Stalin rejected all of this, believing it was a neferious capitalist plot to drive a wedge between him and Hitler. Given the staggering importance of Barbarossa, the Ultra and Magic reports were potenially the most important intelligence coup of the War. And Stalin threw it all away. The result was that the Germans nearly destroyed the Red Army and occupied much of the western Soviet Union with vital industries along with the richest agricultural land in Europe--very nearly winning the War.

For years after World War II, the details of Allied cryptographic work was kept secret. It was the Allies that were primarily successful at code breaking, 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. Histrorians 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. The cracking of the Enigma Machine is perhaps the greatest feat of cryptology and began in Poland a decade before the outbreak of the war. [Bury] The British beginning in 1939 mobilized a substantial effort to crack the Enima codes. Some of the most capable and creative mathematicians in Britain were assigned the enormously difficult task of penetrating German military communications. British cryptanalysts, led by Alan Turing, not only had an impact on the course of the War but in the pricess created the first true computer that would so change the modern world. The naval Enigma machines proved a particularly difficult challenge. Nor did we know just why American carriers showed up at just the right time and place in the Coral Sea or at Midway. Now the complete story of World War II code breaking is known. One area of World war II cryptology that remains a dark hole is Soviet code breaking efforts. The Soviets must have obtained Enima machines as a result of the Red Army offensive before Moscow (December 1941). And the Ruusians are renowned mathemiticians. They did not, however, unlike thre Americans and British did not have 'bombs' early computers. As far as I know, the Russians have never released information on their code breaking efforts.


Historians both during and after the War did not know just why American carriers showed up at just the right time and place in the Coral Sea or at Midway. Neither did the Japanese. The answer of course was Magic. This was the code name for the top-secret code breaking operation which alerted the Ameicans to the Japanese plans. The same American code breaking operation that had learned of the Port Moresby operation, also warned Admiral Nimitz that the next target was Midway. American codebreakers broke into the Japanese Foreign Office's top secret system for sending messages (September 1940). The American cryotolgists named it Purple. The information gained from Purple decryptions came to be called Magic within the U.S. government because the Foreign Office used it for only their most important messages. The location of the Magic operation in Washington meant that information from the decrypts were not sent to Pearl Harbor unless the War Department decided to send some of the intelligence obtained. The Purple machine was a successor to earlier machines used to read Japanese diplomatic mesages. The Navy at Pearl Harbor had its own code breaking operation working on the Japanese naval code--JN-25. Station HYPO at Pearl finally cracked JN-25, leading to the Battle of the Coral Sea and Midway. Midway was the most decisive naval battlr of the War. After Pearl Harbor, American code breakers in cooperation with the British began to focus on German communications.


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 cides. British cryptanalysts, led by Alan Turing, not only had an impact on the course of the War but in the pricess created the first true computer that would so change the modern world.


Canada had its own version of Bletchley Park called the Examination Unit in Ottawa. They hired American crytologists Herbert Osborne Yardley who ran what he called the Black Chamber before and after World War I for the U.S. Army. Yardley after his unit was closed had a following out with the U.S. Government and published a book detailing his work. [Yardley] This caused an international incident because the Japanese learned for the first time tht their codes had been penetrated. There was also information about British code breaking in the book. As a result, Yardley could not get a job with American inelligence even after Japan and Germany began to move toward war and the need increased for signals intelligence. The Canadians, however, hired him for their cryptographic work in the 1930s. After America entered the War (December 1941), both the American and British Government put pressure on the Canadians to dismiss Yaedley which they did. He was replaced by a Oliver Strachey who had been working at Bletchley Park (January 1942). Strachey had refused to go to Ottawa until Yardley had departed the city. He arrived with with keys to high-level French Vichy and Japanese diplomatic codes. We are not entirely sure about why Strachey did this, but suspect that Bletchley Park was so focused on the German Enigma Machine that they were farming out work on lesser priority codes to the Canadians. American and British code breakers had been cooperaring before Pearl Harbor, but Strachey in Ottawa initiated much close cooperation brwtweeen American and British cryptologists. He played a role in breaking the Japanese codes despite the fact that he did not speak Japanese. He finished his work at the Examiination Unit (July 1942).


Estonian Military Intelligence Service worked with the Finnish Intelligence Service before and during the Second World War even though they were invaded and occupied by the Soviets (June 1940) and NAZIS (July 1941).


The Finnish Intelligence Service succeded in compromising Soviet military communications. They also had some success in compromising the classified transmissions of some non-Axis countries. The Finns worked with Japanese cryptologists on Soviet codes.


French code breakers were unable to penetrate the Germn enigma machines. The French effort ws led by Cpt. Gustave Bertrand , head of the French radio intelligence sevice. The French secret service assisted the Poles by getting some code books from a German trsitor. This enabled the Poles to break into enigma until the Germans upgraded the system judt before the War. The Poles did not tell the British and French about what they had accomplished until it became obvious that Hitler was determined to invade Poland. The Poles finally showed Bertrand and Commander Humphrey Sandwith, the Admiralty's chief official dealing with radio interception and direction finding (July 25, 1939). They were stunned when they saw the enigmas the Poles had contructed , but by this time the Pole were againn in the dark. Some of the Polish code breakers managed to escape to France just before Polish resistance to the Germans and Soviets collapsed (late-September 1939). The French set up a joint French-Polish radio intelligence center at Gretz-Armainvillers near Paris making use of the Polish expertise (October 1939). The operation was code named 'Bruno'--Poste de Commandement Bruno. The Bruno center set up a Teletype link to the British Code and Ciphers School (BC&CS) the fore-runner of Bletchly Park. The Bruno operation also included an operation to crack the Spanish and Italian ciphers. [Bury] P.C. Bruno as the Germans advanced was evacuated in stages. The Poles were on the run again. The British were concerned about both the Pole and Bertrand falling into German hands because by this time Bletchly Park had begun to break into some enigma transmissions. GC&CS chief Denniston cabeled Bertrand offering to assist in evacuations. Bertrand had, already got the Poles and some of his staff to Algiers (June 24). He cabeled back and shocked Denniston by telling him that he planned to continue working on enigma. The Franco-German armistace prohibited French military intelligence from working on German codes. Bertrand managed to get permission to continue his work in secret, He set up shop at the Château des Fouzes near Uzès near to the Meditetteranean coast, a site chosen to facilitate a rapid escape if the Germans moved to occupy Vichy. The Poles were surepticiously returned from Algiers (October 1940). Poste de Commandement Cadix was in business. [Budiansky, pp. 145-46.] They continued working until after the Torch landings, the Germans occupoied Vichy (November 1942).


Germany had considerable successes in breaking into the secure traffic of several countries, although World Wr II historians focus primarily on British efforts to crack the German Enigma Machines. Shortly after World War II, the German military launched a new, expanded crypto-analysis capability. The Reichswehr code unit was especially interested in the British Government's telegraph code. This code was used to advise the British Admiralty about the location and movement of non-British naval shipping. As a result of this effort, the Germans before the NAZIs seized power had broken into British, French and Italian naval communications. Even after the NAZI seizure of power and the formation of the Pact of Steel with Italy, the Germans did not advised the Italian Navy that their secure transmissions had been cracked. The German began working informally with the Finnish Intelligence Service to break into Soviet secure communications (at least by 1934). After the Spanish Civil War, Generalissimo Francisco Franco permitted Germany which had supported the Nationalists during the War, to set up wireless surveillance posts in Spain. Their primary purpose was to intercept Royal Navy communications in the Atlantic and Mediterranean. Beginning before the War, the Germans exchanged information with the Italian Servizio Informazione Militare on French secure naval communications. Germany, Hungary and Romania exchanged information on Soviet secure communications efforts. The NAZIs had perhaps the most disorganized war effort of all the major combatant countries. There was a great deal of duplication and ioverlapping jurisdiction in security, research and development, industrial manufacturing, and other areas. Code breaking was another example. One study identified nine different NAZI units involved in cryptology and there may have been more. These units not only wasted scarce resources, but they rarely cooperated fully with each other. Germany's Naval B-Dienst (Beobachtungsdienst - Surveillance Service) was primarily interested in the British Royal Navy. The Germans had some success in reading coded American naval messages through early 1942. This was a factor in the considerabkle success achieved by the German U-boats off the coast of America in the first few months of the War. This ended abruptly with the American military intoduced the SIGABA system (April 1942). SIGANA was similar to Enigma in many ways, but infinitely more complex. The Deutsche Reichspost broke the scrambled voice transmission of the American-British transatlantic telephone system. German technicians built a de-scrambling device and after the Western Offensive (May-June 1940), operated an intercept faciliy at Noordwijk in the occupied Netherlands (1940-41). As a result the Germans were able to regularly listen to classified telephone conversations between U.S. President Roosevelt and Prime Minister Churchill. After D-Day and the Allied push into Belgium and the Netherlands (September 1944), the Germans located the telephone intercept facility from the Netherlands to Bavaria. This severely compromised the intercept capability. B-Dienst was also successful in breaking into Royal Navy's secure communications for much of the War. They cracked the 5-digit Royal Navy code. The British 4 digit naval code proved more difficult to crack, but the Germans did break into it. OKM B-Dienst also sucessfully broke intto five French naval codes and three Danish codes before the outbreak of the the War. Of course a major German target was the Soviet Union. OKM B-Dienst broke four Soviet codes, but the Germans never broke the Soviet diplomatic code. Despite the successes, the Germans never were able to learn about the major Red Army offenses that battered the Wehrmacht on the Eastern Front.


Italy faced several countries in its largely Mediterranean operations, all countries it attacked. They included France, Greece, and Yugoslavia. These countries were all defeated and occupied by the Germans, leaving Britain as Italy's major adversary. The Italians also joined the Germans in their Barbarossa invasion of the Soviet Union. The United States which was aiding Britain was also a target even before Pearl Harbor and Italy's declaration of war aginst America--at Hitler's prompting. As a result America and Britain became Italy primary intelligence targets. Italy was also fighting in the Soviet Union, but the Italian intelligence agencies did not significantlt target the Soviets. Italy made no major codebreaking achievements, but did score some sucesss, primary through traditional spy scraft. Namely the work a special undercover squad that broke into foreign embassies and copied their code books. The Servizio Informazioni Militari (SIM--Italian Military Intelligence) placed its agent working as servants in Rome embasies--all except the Soviet Embassy which had their own servants. Thus the SIM had virtually unrestricted access to the foreign embassies. Thus the Italian General Cesare Ame, in charge of breakins recalled after the War, 'The operation wasn't so difficult. All I had to do was reach for the American Embassy key from my office wall.' There was also cooperation with other country inteligence agenncies (Finland, Hungary, and Germany). There were two Italian crytology agencies. The Italian Army and Navy both had separate units. And they managed to read some foreign crypto-systems. The Army's codebreakers could read the codes of several foreign countries, including the communications of U.S. military attaches. This resulted in Italy's most important World War II code coup. SIM bag men stole the State Bepartment's Black code book. And the U.S. miliary attché in Cairo, Col. Bonner Fellers, used the code to send detailed repors on British operations. Thanks to the SIM, dcrypts were quickly in Rommel's hands-at least some of them. He called them 'die gute Quelle' (the Good Source). The Italians did not share the Black code with the Germans, although they did provide some decoded Black messages. The Germans, from a listening post at Lauf, near Nuremburg in southern Germany, also monitored transmissions from Cairo and were soon cracked the Black code themselves. [Christos T.] The Italian Navy's cryptogists also achieved sone success with Royal Navy codes and cyphers.


The Japanese had an active active cryptographic program. The Army and the Navy had separate programs. They did not manage to crack any major Allied codes. The chief of Imperial Japanese Army intelligence, Lieutenant General Seizo Arisue, told American interrogators after the War, "We couldn't break your codes at all." The did, however break some low-level codes. And with the help of the Finns, they had some success with Soviet codes. Of course until the final week of the War, the Soviets and Japanese were not at war although the border was heavily miitarized. The two countries fought a major battle along the Mongolian/Manchurian bordr just before the outbreak of World War II (July 1939). A faction of the Japanese Army (the Strike North Faction) wanted to attack the Soviet Union, but were undermined by Hitler's decesion to sign the NAZI-Soviet Non-Agression Oacvt (August 1939). After Barbarossa (June 1941), a faction in the Army wanted to join the the Germans in the war with the Soviet Union, but the commitment to the Pacific War persuaded the Gocernment to avoid attacking the Soviets. We have very limited information on Japanese code breaking efforts. As far as we know, their signals intelligence during the Pacific War was limited to traffic analysis, meaning interpreting the volume and direction of signals without understanding the actual messages. The Japanese in debriefings after the War told the mericabns they were unable to cack their codes.


Lithuania and Germany after World War I worked closely together on Polish codes and ciphers and achieved some succes. Both countries had territorial differences with Poland. Cooperation with the Germans ceased after the NAZIs seized power in Germany. The NAZIs wanted the return of Memel. Most of Lithuania hd been part of the Tsarist Empire, but Memel had bee part of East Prussia and transferred to Lithuania as a result of a League of Nations plebecite.


Poles declared their independence in the gfinal days of World War I (October 1918). The borders of the new nation were, however contested by its neigbors, especially Germany and the new Soviet Union. In the West, the League of Nations surpervised referendums, but there were also engagements fought with German militias. In the east there was a full-scale war--the Polish-Soviet War (1919-21). The Polish Cipher Bureau achieved considerable successes cracking Soviet secure communications which ensured the independence of the recently created Polish nation and considerable eastern terrotories. The cracking of the Enigma Machine is perhaps the greatest feat of cryptology and began in Poland nearly two decades before the outbreak of World War II. [Bury] Polish cryptanalysts during the early-1920s had begun intercepting and analyzing German military radio transmissions. Those transmissions suddently became impossible to read, going dark as the cryptologists would pputv it (February 1926). The Poles had no inside information, but they suspected that the Germans had begun to use encrypted (machine generated) codes. [ Budiansky] At the time the new code seemed impossible to crack. We now know that the Germans had begun using their Enigma machines based on machines developed by the German railways. The Germans had considerable confidence in the security of the transmissions made with the codes generarted by Enigma, lsrgely because of the mathematical complexity. One estimate suggests that the internal rotors of Enigma could be wired to generate a complexity of 10 to the 80th power, meaning 1 followed by an astonishing 80 zeroes. This meant a complexity exponetially greater than ever before faced by code breakers in history. The Polish Cipher Bureau thus began the effort to crack the vaunted German Enigma machines. The Poles set out to crack the code amd managed to do so after Allied intelligence managed to provide them an actual Enigma machine. Right before the outbreak of the War the Germans upgraded their Enigma machine, putting the Poles in the dark. After the German invasion (September 1939), the staff of the Polish Cipher Bureau had to split up and try to make their ways to the West. This became very difficult when the Soviets invaded from the east. Some were killed before reaching safety. Others were captured. None revealed the work of the Cipher Bureau to the Germans. Some managed to reach France where the work on Enigma continued. The Germans remained totally unaware that the Poles had suceeded in penetrating Enigma or even had an important codebreaking effort.

Soviet Union

One area of World War II cryptology that remains a dark hole is Soviet code breaking efforts. We have only limited information on Soviet cryptographic efforts during the War. The Soviets must have had a substantial effort. And they must have obtained Enigma machines as early as the Red Army offensive before Moscow (December 1941). The Russians are renowned mathematicians, a critical skill for code breakers. They did not, however, unlike the Americans and British did not have 'bombs' (early computers). As far as we know, the Russians have never released information on their code breaking efforts. There are tantalizing clues that the Soviets may have cracked the Enigma codes. Admiral Golokov, the Soviet CinC in the Arctic, wrote in his 1960 memoirs that he knew that Admiral Fraser was planning to send the Scharnhorst to sea (December 1943). One author who has written extensively about Enigma tells us, "No direct evidence but I don't think the Soviets broke Enigma in any quantity." [Sale] We know that the Soviets knew that the Western Allies had cracked both German Enigma and Japanese codes. They knew about Magic in 1941 and passed the information on to the Germans who informed the Japanese. The Japanese apparently dismissed the reports. The British and Americans passed Magic/Ultra information to the Soviets in 1941 both before and after Barbarossa (without an indication of the source). The specificity and accuracy of these communications must have alerted Soviet intelligence that Enigma was penetrated. Cairncross may have provided the first confirmation of this. Cairncross was assigned to work in Bletchley Park. Every week he relayed summaries of British intelligence intercepts which were of the greatest interest to the Soviet Union. Soviets authors have addressed World War II in great detail, primarily the titanic struggle on the Eastern Front. As far as we know, in the vast Soviet literature, the subject of code breaking is not addressed. Hopefully our Russian readers can confirm this or tell us what has been published on the subject. A Russian correspondent has provided us a review of a Russian book on Soviet cryptology. We are attempting to translate it. It discusses Soviet cryptology in some detail, but not code breaking efforts.


The Germans invaded and occupied Norway (April 1949). And even after defeating the Norwegians and Allies, the Germans maintained a substantial force of some 0.5 million men was eventually maintained there even aftr the Whermacht began to experince manpower shortages on critical front. Hitler was convinced the Allies were planning to invade Norway. The Germans for the first time began using a teleprinter code machine in occupied areas. The Germans used the T52 developed by the German Siemens & Halske electrical engineering compamy. T52 was the Geheimschreiber (secret teleprinter) or Shlüsselfernschreibmaschine (SFM). It used cable circuit (land lines) which for geographic reasons ran through Sweden. While it basically used land lines, those land lines had undersea connectiins connecting Sweden with German occupied Denmark. Unlike Enigma which broadcast messages which could be intercepted, using land lines which more secure as they could not be easily intercepted. The Swedes from the beginning secretly tapped the line (May 1940). The Germans for whatever reason discounted the ability or interest of the Sedens in these messages. They were, however, very itersted and capable. The mathematician and cryptographer Arne Beurling very easily in only 2 weeks cracked the two earliest models. And all he needed was pen and paper. The Swedish telephone company, Ericsson, manufactured comptable machines. They could decode messages once the key settings had been computed by hand. The Swedes were thus able to read traffic in the system for 3 years. And this was not just messages the Germans sent fromm Oslo. They could read Germans messages sent from Finand and the messages the Germans sent from their Stockholm Embassy. The German messages to and from Finland were particularly important. They would have involved messages dealing with the German Barbarossa Plan to invade the Soviet Union. The Swedes manage to intercept some 0.5 million German messages and sucessfully decrypted 350,000 of them before the Germans learned of the Swedish operation. The Germans intoduced a new T52 machine (1942) was the Swedes again defeated. The Germans made more refinements (mid-1943). The Swedes were unable to break the new machine. [Gannon, pp. 157–58.]


Budiansky, Stephen. Battle of Wits: The Complete Story of Codebreaking in World War II

Bury. Jan. "The Greatest Secret of World War II - The Enigma Code Breach".

Gannon, Paul. Colossus: Bletchley Park's Greatest Secret (Atlantic Books: 2006).

Sale, Tony. E-mail message, February 24, 2011.

T., Christos. "Italian codebreakers of WWII," Christos military and intelligence corner (August 29, 2012).

Yardley, Herbert Osborne. The American Black Chamber (1931).


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Created: 5:30 AM 2/23/2011
Last updated: 8:34 AM 2/8/2020