Codeword Overlord
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The Luftnachrichten Abteilung 350 (OKL/LN Abt 350), previously the Chiffrierstelle, Oberbefehlshaber der Luftwaffe (Chi Stelle, O B d L), became the Luftwaffe’s principal SIGINT agency and consisted of eight regiments, including five autonomous SIGINT battalions staffed by 13,000 personnel. LN Regiment 351, commanded by Major Ristow, was responsible for the study of Allied air forces in England and France.
The Luftwaffe organisation provided a comprehensive and continuous order of battle and deployment details of the USAAF and the RAF, drawn mainly from T/A, radio telephone monitoring, and the interception of airborne radar. The solution of the RAF figure codes between March 1940 and 1 November 1942 had been the foundation for all subsequent work which served to betray imminent Allied bomber missions and give advance warning of tactical operations by British and American ground support aircraft. As TICOM summarised, the Luftwaffe accomplished much:
On the western front the solution of the RAF’s Bomber code, Slidex, Syko, and Rekoh through capture and cryptanalysis, gave an advantage to the Luftwaffe which also benefited from breaking the Soviet Air Force’s ground-to-ground 2-figure, 3-figure, and 4-figure administrative and operational codes, and some 5-figure codes which provided the complete Soviet order-of-battle from 1937 until the end of the war. A large amount of intelligence on the Red Army order-of-battle was also obtained from a study of air networks. Abt. 350 also read some Soviet air-ground traffic, air-to-ground radio, telephone monitoring, and from radio direction-finding of bombers in flight, so as to issue accurate warnings of all Russian long-range strategic bombing raids. It also attacked the Soviet Air Army’s 2-figure, 3-figure, and 4-figure traffic, using traffic analysis, monitoring air-to-air radio telephony and from direction-finding of airborne transmitters, supplying early warning of impending Soviet air operations.
On both the western and Russian fronts Abt. 350 issued daily, weekly, or monthly reports to the OKL and the local Luftflotten, with daily and monthly reports that were also sent to their local Wehrmacht counterparts. Monthly reports were delivered to the Army Commander-in-Chief West, to the OKH/GdWA, to the OKM/4 SKL/III, to the OKW/Chi, and also to the Luftwaffe signal intelligence units in the field (LH), which distributed air raid alerts directly to fighter squadrons, anti-aircraft batteries, and the local civilian gauleiters in charge of civilian air raid warnings.
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TICOM’s information about OKM/4 SKL/III was provided by its chief, Wilhelm Tranow, who had worked in naval signals intelligence since his first posting afloat, in 1914 as a radio operator on the Kaisermarine battleship Pommern. He was questioned by TICOM 6 interrogators at Flensburg in May 1945 and gave a comprehensive account of how the B-Dienst, with a staff of 1,000, had conducted T/A, cryptanalysis, and evaluation of British, American, Soviet, French, and Swedish naval traffic. It was supported by a field organisation with a strength of approximately 2,500 that consisted of four detachments in Flanders, Brittany, Wilhemshaven and Pomerania, all engaged in the cryptanalysis of low-level systems, interception and D/F. Each detachment had a total complement of 200 men, including 100 intercept operators and ten cryptanalysts.
OKM/4 SKL/III also manned eighteen primary D/F stations that were actually engaged in interception rather than direction-finding. Each station had a strength of 100, including sixty intercept operators and five cryptanalysts. A further twenty-five secondary D/F stations, each staffed with twenty-six personnel, conducted D/F and T/A.
When TICOM came to assess OKM/4 SKL/III’s performance it learned that the Royal Navy’s Naval Code No. 3 had been read since 1939, and this breakthrough had divulged the Admiralty’s entire wartime disposition and organisation. In the spring of 1940 the solution of Naval Cypher No. 4 had compromised Operation STRATFORD, the proposed Anglo–French expedition to Norway, an event that served as the catalyst for the subsequent German invasion. During that ill-fated campaign access to Naval Cypher No. 4 betrayed detailed information on Allied countermeasures, such as proposed British landing areas, transport arrival schedules, and the deployment of British and French surface ships.
Other OKM/4 SKL/III successes included the solution in 1943 of the British Inter-Departmental Cypher and the reading in 1943 of an RAF torpedo-bomber transposition cipher used for practice exercises in the English Channel, and the solution of various minor Royal Navy and Merchant Navy codes and ciphers.
These Kriegsmarine field units relied largely on D/F to plot the positions of Allied warships and merchantmen, and then inform local commanders. Detachment Flanders, based at Bruges, assisted in February 1942 in the surprise voyage of the battlecruiser Scharnhorst, accompanied by the Gneisenau and Prinz Eugen, when they made their famous dash up the Channel from Brest to Kiel. Six months later, in August 1942, the same detachment read British naval traffic to great advantage during Operation JUBILEE, the disastrous commando raid on Dieppe.
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With a staff of 800, the Oberkommando der Wehrmacht, Chiffrierabteilung (OKH/Chi) intercepted, studied, and evaluated diplomatic, military attaché, and agent traffic, and monitored commercial radio traffic and news broadcasts, while simultaneously maintaining surveillance on all German traffic to ensure security and detect breaches. Operating at least thirteen intercept sites, it received additional radio traffic from other sources, such as the FA, and some landline intercepts. Apart from some military attaché channels, the OKH/Chi left enemy army, navy or air force traffic to its military counterparts, and concentrated on civilian communications. TICOM noted great success between 1939 and 1944 on French systems, and the Hagelin B-211 cipher machine was solved, as were some messages on the French Hagelin BC-58. The important French military attaché code designated FVD was solved early in the war and, as was to be expected, all Vichy systems were compromised from the 1940 surrender when it was filed with the German Armistice Commission in Wiesbaden as part of the terms of the armistice.
The OKH/Chi solved at least four Japanese diplomatic codes, including those designated JAE, JAH and JBA, and in 1938 and 1939 it collaborated with the Foreign Ministry’s Pers Z S to achieve a current solution of daily keys for the Japanese RED cipher machine, and read the US State Department Grey, Brown and A-l Codes. It solved the American Diplomatic Strip Ciphers 0-1 and 0-2, the former in partial fashion based upon a compromise.
Croatian Enigma traffic was solved through compromised machine wiring, and various Polish, Turkish, Greek and Latin American systems were broken extensively. Prior to 1943 appreciable success was achieved in the solution of Italian diplomatic codes.
During the first half of 1944 the OKW/Chi’s most important decrypts, designated Verlaessliche Nachrichten, totalling some 3,000 per month, were distributed to Field Marshal Keitel, to Hitler; and by Keitel to General Jodl. Copies were also sent to the OKW, OKM and OKL, and to their subordinate SIGINT units. Additionally, about forty-five special reports were sent each day to selected recipients, such as the Field Economic Office, the Department of Armed Forces Propaganda, and Eins Heer West.
After 1944 the OKW/Chi, headed by Colonel Mettig, acquired responsibility for issuing cryptographic systems to the Wehrmacht and for inter-service communications. It also took over the task of evaluating the cryptographic systems of other services, and a file belonging to Dr Erich Huettenhain, its chief cryptanalyst, indicated that various studies were made on encrypted teleprinters, Enigma, specially designed Hagelin machines, small cipher devices and hand systems.
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TICOM learned that the most secretive German SIGINT organisation was the Foreign Ministry’s unit, which was divided into two cryptologic sections, the cryptanalytic section, Personal Z Sonderdienst des Auswaertigen Amtes (Pers Z S), and the Cryptographic Section, Personal Z Chiffrierdienst des Auswaertlgen Amtes (Pers Z Chi). Pers Z S had been created in around 1919 and employed a staff of 200 engaged in the study of foreign diplomatic codes and ciphers. According to General Praun, it consisted of thirty-seven desks, each assigned to a particular country:
They were responsible for intercepting and solving messages to and from virtually every country in the world. The Russian diplomatic codes were the most impregnable, and the Russian desk was therefore the most unproductive. Nothing could be learned from Moscow except by intercepting radio dispatches from diplomats accredited to the Russian government. Especially careless were the Turks, whose messages were regularly decoded without effort, even after they had been warned by the Germans.
It operated one small intercept station at Dahlem but collected its raw material from the OKW/Chi, the FA and the Post Office. Pers Z S was also credited with reading almost all the Italian diplomatic ciphers between 1935 and 1942. Additionally, Pers Z S solved two British Foreign Office R Codes, the British Government Telegraph Codes, and read an estimated 75 per cent of the French diplomatic codes. Several major Japanese diplomatic codes were broken, and at least one important Chinese system was solved.
When tackling machine ciphers, Pers Z S solved the Japanese RED machine in 1933 with OKW/Chi assistance. In 1941, following a partial solution by the FA, the Swiss diplomatic Enigma was also solved.
Pers Z S liaised closely with the Pers Z Chi, which devised and distributed the Foreign Ministry’s codes and ciphers, among them several familiar to their Allied adversaries, such as the Deutsches Satzbuch, the Deutsches Seizbuch enciphered by FLORAORA (designated GEC), and the one-time pad known as GEE, all of which were broken.
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The Reichsluftfahrtministerium Forschungsamt (FA), which had been formed in 1935 and headed by Hermann Göring, had been intended as a Nazi organisation to conduct non-military cryptanalysis and exercise a censorship role by tapping telephones in all large German cities, and then in Austria, Denmark, and ‘German Poland’. The FA routinely accessed all German commercial teletype and telegraph lines and after the outbreak of war liaised closely with the censorship authorities, the Abwehr and then the RHSA. According to TICOM’s research, the FA also became the lead investigator of Soviet agent traffic.
As well as studying clandestine signals, the FA monitored the BBC and worldwide radio news broadcasts, and ran six wireless intercept stations of its own, targeted on foreign diplomatic and commercial traffic, and exchanged intercepts with the OKW/Chi, the OKM/4 SKL/III, and probably with the Luftwaffe’s Chi Stelle OBdL. TICOM concluded that the FA, with a staff of 2,000, had solved the Swiss Enigma and broken the Finnish (or Swedish) Hagelin traffic.
Pre-war, the FA had established its reputation by reading French diplomatic messages, which had indicated that, in the absence of British support, Paris did not intend to oppose the Austrian Anschluss with force. During the 1938 Munich crisis, the FA had read Neville Chamberlain’s messages to the Foreign Office in London, and Hitler apparently had once delayed a conference with the prime minister for several hours so he could see the relevant decrypts.
The FA was also credited with breaking into a Russian internal communications network, which had revealed bottlenecks in the Soviet military supply system. FA summaries were circulated through special liaison personnel to Hitler, Göring, Keitel and Jodl, Foreign Minister Ribbentrop, and to Admiral Dönitz. Deliveries were also made to selected recipients in the Foreign Ministry, the OKW, the RHSA, the Economic Ministry, Ministry for War Production, and the Propaganda Ministry.
The FA co-operated with the Pers Z S on the exchange of code group identifications, additives and enciphering keys, and frequently exchanged technical information on English, Italian and Vatican systems, and cross-posted selected personnel.
During its investigation of the FA, TICOM could only trace about twenty former employees with whom to conduct interviews, so not everything was learned about the organisation. In comparison, there was much greater success in researching the armed forces, where field collaboration had been considerable. Eastern front reports showed a detailed operational co-operation between the Luftwaffe’s LN Regt 353, the Wehrmacht’s KONA 1 and the Kriegsmarine units dealing with Soviet Black Sea Fleet traffic. The Wehrmacht’s KONA 5 worked closely with the Luftwaffe’s counterparts in the west, at Paris and Noisy. Between 1940 and 1942 the OKM/4 SKL III and the Luftwaffe’s Chl-Stelle OBdL, and the OKW/Chi, and FA, all collaborated on the solution of the English Inter-departmental Cipher. There was also FA–OKM/4 SKL/III co-operation on the solution of the British Government Telegraph Code (South Africa) and Bentley’s Code. The Wehrmacht’s In 7/ VI actually worked on Turkish diplomatic traffic, by agreement with the FA, and had KONA 4 intercept this traffic for them.
In 1942 Professor Peschenny of the OKW/Chi and a group of his cryptanalysts were transferred to Intercept Control Station East (HL-3), one of the predecessors of the OKH/OdNA, for work on the main Red Army five-figure code. In another striking example of inter-service co-operation, the Kriegsmarine commander in the Aegean placed his radar intercept personnel and equipment under the command of LN Rgt 352. On another occasion LN Rgt 353 personnel went aboard the cruiser Prinz Eugen to monitor traffic from the Soviet Baltic Fleet’s air arm. In 1939 Dr Hüttenhain of the OKW/Chi had been transferred temporarily to the Wehrmacht to work on the solution of French military systems, and in the spring of 1942 OKM/4 SKL III exchanged personnel with the Wehrmacht and Luftwaffe in order to acquire trained Hollerith operators.5
The Wehrmacht’s Inspektion 7/lV pioneered the use of IBM (Hollerith) equipment, and its facilities had been set up in the winter of 1939/40 by the OKH/GdHA’s predecessors. The OKH/Chi never owned its own Hollerith hardware and instead used the Wehrmacht’s. In 1944 the OKW/Chi developed a number of decoding devices, some of which were handed over to the other agencies, including the Digraph Weight Recorder (Bigrammsuchgeraet), which was made available to the Wetternachrichten Überwachung (German Weather Service, WENUEB).
The FA occasionally provided the Chi Stelle OBdL with traffic, although TICOM was unable to establish the quantities involved, and passed some intercepted commercial traffic of naval interest to OKM/4 SKL/III. The Kriegsmarine passed its weather intercepts to the Luftwaffe, which would acquire some inter-service responsibility for the solution of weather traffic. On operational fronts, when Wehrmacht search receivers encountered air force frequencies, the relevant information was shared. It also appeared that the OKW/Chi controlled a clandestine naval D/F station in Spain.
TICOM discovered that there had been an extensive German effort directed against agent and partisan systems that was shared by the OKW/Chi, Inspektorate 7/VI and perhaps the FA, and a small organisation that did little or no cryptanalysis, the OKW/NV/FU III, headed by Major von Bary.6 The comparatively dysfunctional relationship between these agencies demonstrated to TICOM that inter-departmental collaboration in interception and cryptanalysis was very uneven, and was handled individually, on a case-by-case basis, rather than by some centrally imposed authority. This approach, in stark contrast to the centralised discipline adopted by the Allies, served to exacerbate liaison problems.
Initially, at the outbreak of war, responsibility for the monitoring of clandestine transmissions within Germany and the occupied territories was borne by the Funkabwehr (OKW/NV/FU III, or FU III). However, in spring 1942 the Funkabwehr, headed by Hans Kopp, had pressed for its own cryptanalytic section, but none of the existing service agencies had supported the proposal and instead a section dedicated to the cryptanalysis of agent traffic was established within Inspectorate 7/VI that became known as the Referat Vauck, after its chief, Richard Vauck. Originally located in Berlin, it was moved in the autumn of 1943 with FU III to Dorf-Zinna, near Juterborg, and was transferred again a year later from Inspectorate 7/VI to the newly formed OKH/GdNA.
The Referat Vauck did not exercise a complete monopoly on agent cryptanalysis and most of its efforts, and those of FU III, were concentrated on agent networks in France and Belgium. Further east, in the Balkans, the task was shared between the Referat Vauck, handling Soviet partisan traffic between mid 1942 and mid 1943, and a separate specialist section headed by KONA 6’s Lieutnant Schubert, who would ultimately transfe
r to the OKW/GdHA where he took over eastern front cryptanalysis, studying NKVD partisan communications. However, Yugoslav circuits were intercepted and read by a KONA 4 detachment in Belgrade, and the more difficult Balkan systems were studied in Berlin by a dedicated Balkan section known as Referat Ballovic of Inspektorate 7/Vl.
Referat Vauck’s work on the principal cipher system used by the Polish government-in-exile in London to communicate with Warsaw achieved success in 1943, and in the autumn of that year eight members of the section were transferred to the OKK/Chi’s Polish Section. FU III’s interception role was enhanced by the OKW/Chi site at Lauf, and the cryptanalytic attack was supported with IBM equipment provided by Inspektorate 7/Vl.
When interviewed by TICOM, Leutnant Schubert mentioned only one example of the FA’s participation in his work, recalling that in January 1945, the FA’s Senior Specialist Wenzel had been sent by the FU 111 to the OKH/GdNA to concentrate on resistance circuits.
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TICOM’s study of the enemy’s SIGINT organisations extended to Germany’s Axis partners, of which the Italians were the most advanced, but the least trusted. Prior to the September 1943 armistice there were four Italian cryptologic agencies, the two most important being the Cryptanalytic Section of the Servizio Informazioni Militar (SIM) and the Cryptanalytic Section of the Navy’s Servizio Informazioni Speciali (SIS). The Foreign Ministry maintained a small cryptographic office, the Ufficio Crittografico, to compile Italian diplomatic codes and ciphers. The Inspector-General of Political Police in the Ministry of the Interior (Publica Sicurezza) also maintained a cryptanalytic section to deal with ‘Communist’ and ‘foreign agent’ codes and ciphers. The Italian Air Force Intelligence, the Servizio Informazioni Aeronautica (SIA), maintained its own intercept organisations but no cryptanalytic capability, relying on the Air Force for assistance. As TICOM’s analysts observed: