In the course of WWII both the Allies and the Axis powers were able to gain information of great value from reading their enemies secret communications. In Britain the codebreakers of Bletchley Park solved several enemy systems with the most important ones being the German Enigma and Tunny cipher machines and the Italian C-38m. Codebreaking played a role in the Battle of the Atlantic, the North Africa Campaign and the Normandy invasion.

In the United States the Army and Navy codebreakers solved many Japanese cryptosystems and used this advantage in battle. The great victory at Midway would probably not have been possible if the Americans had not solved the Japanese Navy’s JN25 code.

On the other side of the hill the codebreakers of Germany, Japan, Italy and Finland also solved many important enemy cryptosystems both military and diplomatic. The German codebreakers could eavesdrop on the radio-telephone conversations of Franklin Roosevelt and Winston Churchill, they could decode the messages of the British and US Navies during their convoy operations in the Atlantic and together with the Japanese and Finns they could solve State Department messages (both low and high level)  from embassies around the world.

Radio intelligence and codebreaking played an important role not only in the military and diplomatic fields but also in the shadow war between the Allied intelligence agencies, the European Resistance movements and the German security services. In the period 1939-41 German troops conquered most of continental Europe and the occupied countries were forced to contribute to the Axis effort by sending raw materials, agricultural products and forced labor to Germany. Thanks to the blockade of German occupied Europe by the Royal Navy and the harsh demands of the German authorities life in the occupied areas was bleak. Discontent over German occupation led many people to join resistance movements and oppose the authorities, either by printing and distributing anti-Axis leaflets and books, by sabotaging war production or by directly attacking the German troops and their collaborators in the government and the civil service.

The British intelligence services SIS - Secret Intelligence Service and SOE - Special Operations Executive helped organize and fund the resistance movements and they even supplied them with weapons through airdrops. Besides sending their own intelligence teams into occupied Europe and working together with the home grown resistance movements they also collaborated with the intelligence services of the European Governments in Exile, most of whom where based in London during the war.

The British agencies SIS and SOE were not the only Allied organizations sending spies into Europe and supporting the growing resistance movements. The American OSS - Office of Strategic Services also conducted its own operations in occupied countries and so did the intelligence department of the Polish General Staff.

The German security services and the Radio Defense Corps

The German agencies tasked with securing the occupied territories and opposing the Allied intelligence agencies and resistance movements were the military intelligence service Abwehr, the political security service Sicherheitsdienst, the secret military police Geheime Feldpolizeiand the Radio Defense departments of the Armed Forces and the Police.

The OKW Funkabwehr

The High Command of the Armed Forces – OKW (Oberkommando der Wehrmacht) had a radio defense department tasked with signals security and the interception of illicit radio transmissions. The department was part of the OKW signals directorate and its designation was OKW/WFSt/WNV/FU III. WNV/FU III was a militarized organization and cooperated closely with the Army’s signal service. Apart from fixed intercept and direction finding stations they also had five mobile units, the 612, 615, 616 Intercept Companies and the 1st and 2nd (GAF) Special Intercept Companies (1).

The OKW Funkabwehr was responsible for the monitoring of illicit radio transmissions in Northern France, Belgium, Southern Holland, Italy, the Balkans and parts of the Eastern Front. Regional branch offices (Aussenstellen) were established at Paris, Lyon, Brussels, Oslo, Vienna, Warsaw, Rome, Prague, Athens, Belgrade, Bratislava, Klagenfurt and Varna.

An undercover Funkabwehr station operated in Madrid, Spain and cooperated with the Spanish intelligence services.

The Order Police Funkabwehr

The civilian police force Ordnungspolizei(Order Police) set up its own radio defense department in the late 1920’s and according to postwar reports there were fixed intercept stations (Beobachtungsstellen) at Berlin-Spandau, Cologne, Constance, Vienna, Nuremberg and Oldenburg plus mobile units called Polizei Funkaufklärungskompanien. During the war the organization was expanded in order to counter the rising numbers of Allied agents and Orpo Funkabwehr units were responsible for the monitoring of illicit radio transmissions in Southern France, Holland, Norway, Germany and parts of the Eastern Front (2).

Both the OKW and the Ordnungspolizei Funkabwehr departments cooperated with the security services (3) and although there were rivalries and duplication of effort it seems that there was regular exchange of information, at the top level, on agents’ details and cipher systems (4). On the other hand cooperation between WNV/FU III and Orpo field stations depended on the local conditions (5).

Breaking Allied agents codes

The Radio Defense departments of the OKW and Ordnungspolizei monitored the airwaves for unidentified radio traffic and used direction finding equipment in order to locate the sites of agents transmissions. The technology of that era could not pinpoint the exact location so the fixed intercept stations were used to identify the general area and then mobile units were dispatched to find the exact building housing the agent. In some cases it was necessary to use even more advanced means such as the gürtel snifter, which was worn by German personnel over a coat (6).

Allied agents kept in contact with their controlling stations abroad through the use of undercover radio stations. The information they gathered as well as their orders from HQ were transmitted over the airwaves. Messages were enciphered with a variety of systems in order to protect the contents from the Germans. According to information available from British and German reports the main system used by Allied agents in Western Europe was the double transposition, using a poem as a ‘key’ generator (7).

The German security services tried to arrest enemy radio operators and capture their cipher material. Then it was possible to decipher past and current traffic and even attempt a ‘radiogame’. By having access to the agents radio procedures and cipher systems it was possible, at times, to continue their transmissions and thus learn of the plans and operations of the enemy intelligence services. The ‘radiogame’ could be conducted either by the captured agent (provided he/she was willing to cooperate with the Germans) or by experienced German radio operators who could mimic the agent’s radio ‘fingerprint’ (8).

Apart from physical compromise agents systems could also be solved cryptanalytically, however analysis of agents ciphers was in some ways more difficult than with Allied military and diplomatic systems. Large organizations used specific cipher systems and followed certain rules. This made the work of enemy codebreakers easier in the sense that they already knew what they were up against (an enciphered codebook, or a transposition cipher or a strip cipher etc). Large organizations also generated lots of traffic that could be used to find errors, repetitions and ‘depths’. When it came to agents codes however these rules did not apply. There were few messages to analyze, the cipher systems were not fixed but underwent changes and each Allied agent used his cipher systems with slight modifications that made solution very difficult.

Despite these conditions it was still possible for the Germans to solve a substantial amount of Allied agents traffic through cryptanalysis. Originally the OKW Funkabwehr relied on OKW/Chi - (Oberkommando der Wehrmacht/Chiffrier Abteilung) Signal Intelligence Agency of the Supreme Command of the Armed Forces for the analysis of agents ciphers but it seems that since OKW/Chi was primarily engaged with the solution of diplomatic and military attaché ciphers the agents messages received only scant attention (9).

The Ordnungspolizei Funkabwehr cooperated with Goering’s Forschungsamt on Russian agents codes but this also seems to have been a limited effort on behalf of the FA (10).

Things changed in early 1942 when the analysis and solution of agents traffic was taken over by a new department of the German Army’s codebreaking agency Inspectorate 7/VI. Department 12 (Referat 12) was created to work on agents systems and pass the results to the security services and the radio defense departments.

Inspectorate 7/VI - Referat 12 (Agents Section)

During WWII the German Army made extensive use of signals intelligence and codebreaking in its operations against the Allied powers. German commanders relied on signals intelligence in order to ascertain the Allied order of battle and track the movements of enemy units.

The German Army’s signal intelligence agency operated a number of fixed intercept stations and also had mobile units assigned to Army Groups. These units were called KONA (Kommandeur der Nachrichtenaufklärung) - Signals Intelligence Regiment and each had an evaluation centre, a stationary intercept company, two long range signal intelligence companies and two close range signal intelligence companies (11).

The Army’s KONA units were primarily engaged with the interception and analysis of Allied military traffic but in some areas they also covered agents/partisans traffic.

In the Soviet Union KONA 6 monitored partisan traffic and from mid 1943 was able to read their enciphered communications with Moscow. In the Balkans KONA 4 intercepted and decoded (with the assistance  of Inspectorate 7/VI’s Referat 6) a large volume of Tito, Mihailović and British agents traffic.

The KONA units did not have the ability to solve complicated Allied cryptosystems. Instead they focused on exploiting low/mid level ciphers and even in this capacity they were assisted by material sent to them by the central cryptanalytic department. This was the German Army High Command’s Inspectorate 7/VI.

Inspectorate 7/VI had separate departments for the main Allied countries, for cipher security, cipher research and for mechanical cryptanalysis (using punch card machines and more specialized equipment).

The War Diary of Inspectorate 7/VI shows that in the first half of 1942 the solution of agents traffic was officially taken up by the department, with a summary of work on Agents systems filed under the progress report of Referat 1 (12). In August the new Department 12 was created to deal exclusively with agents systems.

Head of the department was 1st Lieutenant Dr Wilhelm Vauck, a mathematician of Dresden University (13). According to postwar TICOM reports dr Vauck was a talented cryptanalyst who got along well with his subordinates (14).  The strength of the unit rose from 26 people in August 1942 to 40 in December 1943. From late 1942 the unit also started sending two-man teams to regional Aussenstellen in Paris, Marseilles, Lyons, Prague, Oslo, Vienna, Brussels so that captured material could be exploited without delay. In November 1943 the entire department was moved close to the OKW Funkabwehr HQ at Dorf Zinna, Jüterbog and became subordinate to OKW/Chi as Referat X (15).

Available sources on the work of Referat 12

Information on the work of Referat 12 is available from its monthly reports, included in the War Diary of Inspectorate 7/VI and from postwar interrogations of German personnel that either worked at Referat 12 or were acquainted with their operations.

The reports of the period April 1942-February 1944 are available from the War Diary of Inspectorate 7/VI but unfortunately the rest are missing (or are included in the files of OKW/Chi). Obviously the most reliable sources are the reports from the War Diary, however these are not always easy to interpret since they use codenames for the intercepted agents radio links.

Regarding the postwar interrogations of German personnel, the most useful are:

1). TICOM report I-115 by Major Mettig (head of the army’s signal intelligence service in the period 1941-43).

2). CSDIC (UK) SIR 1106 by Miersemann (a member of Referat 12).

3). CSDIC/CMF/SD 80 by Lentz and Kurfess (members of Referat 12 detached to Aussenstelle Paris).

4). TICOM report I-180 by Keller (a member of Referat 12).

5). Chapter ‘Radio Counterintelligence’ of Foreign Military Studies P-038 'German Radio Intelligence', written by Lieutenant Colonel de Bary, head of the OKW Funkabwehr in the period 1942-45.

6). Part 3 of ‘War Secrets in the Ether’ by Wilhelm Flicke (member of the OKW/Chi intercept department).

Unfortunately the postwar interrogations of dr Vauck have not been released by either GCHQ or the NSA.

Overview of important cases

Using the monthly reports of Referat 12 it is possible to give an overview of its successes:

Eastern networks

Red Orchestra – Rote Kapelle

From the 1920’s the Soviet Union financed and organized the creation of spy networks throughout Europe. These penetrated military, economic, political and diplomatic circles. Many of the agents were devoted communists who thought they were working for the creation of a better world. Germany was a major target of the Soviet spies, especially after power was seized by the NSDAP party. The Germans called these networks the ‘Red Orchestra’.

Inside Germany there were three main spy networks in Berlin. The ‘SENIOR’ network under Luftwaffe officer Harro Schulze-Boysen, the ‘CORSICAN’ network under economist Arvid Harnack and the ‘OLD MAN’ network under writer Adam Kuckhoff. These groups were well placed to provide important intelligence to Moscow. Harnack had a high ranking position in the economics ministry and Schulze-Boysen was assigned to the liaison staff of the Luftwaffe Chiefs of Staff.

From Harnack came information on the German economy such as investments abroad, foreign debt, secret trade agreements with other countries, currency deals etc. His network also controlled an Abwehr officer assigned at OKW headquarters and a lieutenant in German naval intelligence. Boysen’s position gave him access to classified reports prepared for the Luftwaffe high command.

After the German attack on the Soviet Union, in summer 1941, the closure of the Soviet embassies meant that the intelligence networks could not communicate with Moscow through the embassy personnel but instead had to use their undercover radio facilities. Their overreliance on radio communications means that too many messages were sent from the same stations and thus they attracted the attention of the Radio Defense Corps.

One such radio center was raided on 12 December 1941 in Brussels. With the aid of captured cipher material messages were decoded and names were identified. This was the beginning of the end for the Soviet spy networks in Western Europe. In June and July 1942 more cipher documents were retrieved by the Germans and the names of members of the Berlin Rote Kapelle decoded. Overall in 1942 130 members of the Berlin Rote Kapelle networks were arrested and 49 of them executed. The leaders of the organization Leopold Trepper and Anatoly Gurevich were arrested in December 1942 and November 1942 respectively. Henri Robinson, head of the French and UK networks, was also arrested in 1942.

The reports of Referat 12 for May - September ‘42 show the investigation of messages of the ‘Kapelle Etterbeck’/’Kominternsender Brussels’ (Brussels radio station), their solution, the identification of individual agents and cooperation with Sicherheitsdienst officials on a ‘radiogame’.

May 1942

July 1942

September 1942

The solution of these messages showed that the Rote Kapelle even had two agents inside Referat 12!

Operations Eiffel and Mars

After dismantling the Rote Kapelle networks the Germans initiated a ‘radiogame’ whereby their own personnel would prepare reports and send them using the Russian cipher systems. Anatoly Gurevich, who was second in command of the Rote Kapelle network, cooperated with the Germans and thus messages and orders were exchanged between the Germans and Moscow.

These operations were called ‘Eiffel’ (for the radio station in Paris) and ‘Mars’ (for the radio station in Marseilles) (16).

Report of March 1943

Red Three – Rote Drei

In the period 1941-42 not all Rote Kapelle networks were dismantled by the Germans. In neutral Switzerland a spy group headed by Alexander Rado was able to gather intelligence on political, economic and military developments and transmit reports to Moscow via three radio stations. Two of the transmitters were in Geneva and one in Lausanne. The Germans called this network the Red Three (Rote Drei) and made attempts to penetrate the organization with their agents, since they couldn’t attack them directly due to Swiss neutrality.

In the second half of 1943 the Germans were finally able to convince the Swiss authorities to take action against these unauthorized transmitters and the Swiss radio security service located two of them and captured members of Rado’s organization. Then they initiated a ‘radiogame’ using the captured radio stations and cipher material (17).

The Red Three group had access to valuable information and it is possible that they had sources inside the German High Command. It seems that from 1941 till late 1943-early 1944 around 4.000 -5.000 messages were sent to Moscow (18). The Germans investigated this traffic but solution came relatively late in April 1943.

The reports of Referat 12 and the files of Erich Hüttenhain, chief cryptanalyst of OKW/Chi, show that in February 1943 both departments started investigating this traffic (Swiss WNA net with transmitters 3112, 3106 and 3116) and both were able to solve messages in April ’43 (19).


Referat 12- February 1943

Referat 12- April 1943

Messages continued to be solved in the following months with the report of February 1944 saying:

‘65 messages of the Rote Drei were decrypted, so that now 382 broken messages are available. The order for a cipher change — transition to fixed mixed Caesars — was detected in mid-December. The change of the cipher key book happened already at the beginning of August 42. The key for the Sissy-messages resulted in the solution of a message from December 42.’

According to the Center for the Study of Intelligence article: ‘The Rote Drei: Getting Behind the 'Lucy' Myth’, there are 437 decrypted messages available from German sources.

Czech mbm network

The Czech resistance movement and the Czech intelligence service caused serious problems for the German authorities with their most audacious operation being the assassination of Reinhard Heydrich, protector of Bohemia and Moravia and former head of the Reich Main Security Office. However after this episode the Germans took many security measures and were generally able to keep the resistance activities under control. Keeping the Czech areas pacified was particularly important since Czechoslovakia had a developed heavy industry sector which produced weapons for the German armed forces.

In their counterintelligence operations the Germans benefitted from having the ability to read a substantial amount of the traffic exchanged between the Czech IS in Britain and the Czech resistance in the occupied territories. This case has been covered in detail in Svetova Revoluce and the codes of the Czech resistance.

Polish PS networks

In WWII Poland fought on the side of the Allies and suffered for it since it was the first country occupied by Nazi Germany. In the period 1940-45 the Polish Government in Exile and its military forces contributed to the Allied cause by taking part in multiple campaigns of war. Polish pilots fought for the RAF during the Battle of Britain, Polish troops fought in N.Africa, Italy and Western Europe and the Polish intelligence service operated in occupied Europe and even had agents inside the German High Command.

Although it is not widely known the Polish intelligence service had spy networks operating throughout Europe and the Middle East. The Poles established their own spy networks and also cooperated with foreign agencies such as Britain’s Secret Intelligence Service and Special Operations Executive, the American Office of Strategic Services and even the Japanese intelligence service. During the war the Poles supplied roughly 80.000 reports to the British intelligence services (20), including information on the German V-weapons (V-1 cruise missile and V-2 rocket) and reports from the German High Command (though the agent ‘Knopf’) (21).

The communications of the Polish IS became a major target for the German codebreakers and messages of their military attaché service, intelligence department and resistance movement were read throughout WWII. The reports of Referat 12 show that the Polish networks were called PS nets by the Germans and  after investigation of their cipher procedures in July and August 1942 the first messages of line 22 (polnischer Agentenfunk) were solved in September ’42.

In November ’42 the solved cipher material was sent to the Vienna ABP office (Ausland Brief Prüfstelle – Postal censor office) so that that spy case ‘olczyk’ could be solved and members of Referat 12 visited the Warsaw Abwehr office in order to teach their personnel how to decode messages of the line 22. According to the next report the Abwehr was only supposed to decode messages using the material provided by Referat 12, they did not have permission to do cryptanalysis on their own. In December changes in the additive procedure made solution difficult and there was cooperation with OKW/Chi. In 1943 the traffic continued to be solved despite changes in the cipher procedure. Messages of the line 22 network ‘Martha’ operating from Lyon, France were solved in February and in June the line 21 was also solved. In the second half of 1943 the reports show the solution of messages from the lines 6521, 6508 (Bucharest-Istanbul), 6003, 6008, 6509. In November the team processing the Polish material remained in Berlin and came under the control of OKW/Chi.

According to Major Mettig, the solution of Polish systems (especially on the link London-Warsaw) was the outstanding achievement of Referat 12 (22).

The Western LCA networks

The efforts of Referat 12 were split between Eastern and Western spy networks. In the Western areas of Europe the traffic of the LCA networks (radio links from the UK to France, Belgium, Holland, Denmark, Norway) was intercepted, processed and decoded. These groups were controlled by the British intelligence services SIS and SOE or by the intelligence services of the European governments in Exile.

The main cipher system used by Allied agents was the double transposition, using a poem or a book as a ‘key’ generator. This system offered adequate security, provided it was used properly but was vulnerable to mistakes in encipherment and transmission errors. According to Leo Marks, head of the SOE’s cipher department, in July 1942 a quarter of all incoming messages were indecipherable due to ‘careless coding or acute Morse mutilation’ (23). The German codebreakers also faced the same problems against these messages with the report of May 1942 mentioning transmission and encryption errors:

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