B-Dienst
The B-Dienst, also called xB-Dienst, X-B-Dienst and χB-Dienst, was a Department of the German Naval Intelligence Service of the OKM that dealt with the interception and recording, decoding and analysis of the enemy. In particular, it focused on British radio communications before and during World War II. B-Dienst worked on cryptanalysis and deciphering of enemy and neutral states' message traffic and security control of Kriegsmarine key processes and machinery.
B-Dienst was instrumental in moulding Wehrmacht operations during the Battles of Norway and France in spring 1940, primarily due to the cryptanalysis successes it had achieved against early and less secure British Naval ciphers.
B-Dienst broke British Naval Combined Cypher No. 3 in October 1941, which was used to encrypt all communications between naval personnel, for Allied North Atlantic convoys. This enabled B-Dienst to provide valuable signals intelligence for the German Navy in the Battle of the Atlantic. The intelligence flow largely ended when the Admiralty introduced Naval Cipher No. 5 on 10 June 1943. The new cipher became secure in January 1944 with the introduction of the Stencil Subtractor system which was used to recipher it.
Background
The B-Dienst unit began as the German Radio Monitoring Service, or educational and news analysis service, by the end of World War I in 1918, as part of the navy of the German Empire.A counterpart to the B service on the British side was the Y-service or Y Service. The Y was onomatopoeic for the initial syllable of the word wireless, similar to the B initial for the German service.
Little was known outside about the internal organization and workings of the B-Dienst section. After the armistice of Italy, officers of the Italian naval communications intelligence in conversation with the allies, informed them that even though they had worked in close collaboration with B-Dienst, they had little understanding of the workings or internal structure of B-Dienst, thereby affirming the secretive nature of the organization and its effective security.
B-Dienst personnel numbered around 5000 people by the end of 1944. B-Dienst originally started as the 3rd section of the 3 Naval Operations of the OKM, became part of the 2/SKL, stayed with 2/SKL when it rose to a division, and became in effect 4/SKL. Technically it was the Radio Reconnaissance Branch of the Naval Communications Services Division.
In 1938 before the start of the war, B-Dienst had insufficient personnel to work on the more complex ciphers, so instead concentrated on the Royal Navy Administrative Code, which was a 5-figure code reciphered on a subtractor table. By October 1939, B-Dienst had around 40 men working at the English desk on Naval Cypher, specifically in those areas that interested them, i.e. North Sea and the Atlantic. By the time of the British expeditionary force to Norway, personnel had almost doubled. By the end of 1940, numbers increased again to 150. Service personnel were recruited from all areas of the armed forces, specifically those who had foreign language skills and were given a short six week training course. By December 1942, the English desk had 275 personnel employed, and around 300–360 cryptanalysts by spring 1943, which was the peak. Including clerks and evaluators, the number was around 1100. From 1942 onwards, due to the high demand for men at the front, B-Dienst was forced to employ women cryptographers. By the end of the war, employment was split at 50% women and 50% men.
The B-Dienst organization worked over a 24-hour period from the beginning of the war to the last months. The duty cycle for each person consisted of an eight hour shift, working in the order of three days, three evenings and three nights. The number of military personnel working per watch depended on the code being worked on, but at the end was around 80 men. For Naval Code, which was used by the Royal Navy for administrative purposes, it was slightly less; for Naval Cypher which was used by the Royal Navy for operational purposes, it was slightly more.
During World War II, B-Dienst was located in 72–76 Tirpitzufer in Berlin, which was later renamed Bendlerblock, until it was bombed in December 1943, when they re-located to a bunker outside the city, which was code-named BISMARCK. Its location was communicated to the Kriegsmarine in an Enigma key called FREYA. The bombing of Berlin in 1943 destroyed large parts of B-Dienst records, markedly reducing their operational efficiency and forcing them to move to the town of Sengwarden near Eberswalde, located about 50 km northeast of Berlin. Forced again to move in the spring of 1945, due to the Russian advance, they first moved to Aurich, a town in Lower Saxony, then to the Intercept Station at Neumünster and finally moved to the Signals School at Flensburg. TICOM located them on 17 May 1945.
Key personnel
Kurt Fricke
Admiral Kurt Fricke was Chief of Operations of Naval War Command. Kurt Fricke ran the major enquiry which investigated the sinking of the German auxiliary cruiser, colloquially known as an armed raider, the Atlantis in the context of Enigma security. Fricke exculpated both Naval Enigma security and treason of senior staff of the Atlantis, at a time when Naval Enigma was undergoing extensive cryptanalysis by the British Government Code and Cypher School at Bletchley Park. Fricke also investigated the sinking of the German battleship Tirpitz and a number of other sinkings. Fricke was killed on 2 May 1945 during the Battle of Berlin.Ludwig Stummel
had succeeded Theodor Arps as Group Director of Naval Warfare department: Communications from 1 January 1940 to 15 June 1941. Ludwig Stummel was a career signals officer who had joined the Navy during World War I. A fervent Nazi and Catholic during the run-up to the war, he increasingly became disaffected with the regime as the excesses of the regime offended his religion. As well as running the B-Dienst cipher bureau, one of the responsibilities of group heads was to investigate situations in which the Naval Enigma and keying procedures could be compromised and take appropriate action. Between 16 June 1941 and May 1943, Vice Admiral Erhard Maertens took responsibility for the position becoming Stummel's immediate superior. Ludwig Stummel, now promoted to rear admiral, took over the position when Erhard Maertens was sacked. Stummel was Group Director from May 1943 to 16 August 1944 and Rear Admiral Fritz Krauss was in charge from 16 August 1944 to 22 July 1945.Heinz Bonatz
was Chief of German Naval Radio Intelligence, head of Group III of 4/SKL of OKM, which was responsible for cryptanalysis of enemy signals. An energetic man, he joined B-Dienst in February 1934.Wilhelm Tranow
The most important individual at B-Dienst was former radio man and energetic cryptologist Oberregierungsrat Captain Wilhelm Tranow, head of the English language cryptanalysts. The American military historian of cryptography David Kahn stated:Wilhelm Tranow was in charge of section IIIF of group III of 4/SKL of OKM, which was the English desk, and was responsible for the interception of enemy radio communications, the evaluation of those enemy crypts, and the deciphering of enemy crypts. The organization of the German radio security processes was another important responsibility.
Other notable personnel
Two other important individuals at B-Dienst, who were successful cryptologists, were Lothar Franke, who was responsible for the French desk, and Paul August for the Italian desk.Organization
By August 1944, B-Dienst as an organization with OKM had enough personnel to qualify as a division, and the Order of battle within 4/SKL of OKM was as follows:All high-grade traffic was forwarded to 4/SKL in Berlin, together with direction finding results, traffic analysis and low-grade decoding results.
The Office of Naval Communications was commanded by Konteradmiral Krauss between 16 August 1944 and 22 July 1945. 4/SKL was subdivided as follows:
General Section 4/SKL I
Central Office. Commanded by Korvettenkapitän z. V. Jensen, Central Office has three subsections. The central sections function was one of administration.- Section Ia: This section answered general questions relating to the organization, managed the training and utilization of officers of the service, and managed the registration and classification of documents.
- Section Ib: This section dealt with the training and utilization of petty officers, men and women auxiliaries of the service, with the exception of the line telegraphy unit personnel. It was also responsible for the defence of the Marine Military Radio.
- Section Ic: Training and utilization of all other personnel in 4/SKL not covered by sections Ia and Ib. Setting up and organizing line telegraphy units.
- Section Iz: This section was responsible for the personal matters of officials and employees of the Office and of officials of the radio intelligence service at subordinate stations.
General Section 4/SKL II
- Section IIa: Its responsibility was also one of liaison, specifically with 1/Skl and with any other departments which needed operational, tactical or general questions answered. It managed the cooperation between 4/SKL and allied navies. Responsible for operation secrecy of the service.
- Section IIb: This section answered all questions related to the radio service. It was responsible for the application of radio communication technologies for naval warfare, which included camouflage, deception and radio jamming. It also managed the execution of the radio teleprinter service.
- Section IIc: Its areas of concern were development, production and distribution of cipher material, cipher systems, cipher keys and all necessary operational aids.
- Section IId: It was responsible for monitoring German cryptographic material from the standpoint of enemy radio intelligence, development of new machine methods for encipherment; development of new inventions in the field of cryptography.
- Section IIe: This section managed the Optical Communications Service, the Recognition Signals system, which was used to ensure that friendly units could recognize each other at sea, and they managed the update and publishing of the Signal Book of the Navy.
- Section IIf: This section ran the communications service for the German Merchant Marine in wartime; the international and public radio service for B-Dienst, and the official B-Dienst radio service. It also managed the Relay message service, the Nautical Naval Communications Service and the sea distress reporting service.
- Section IIW: This section worked on all operational aspects and problems of transmission in the meteorological service i.e. the distribution of instruments, preparation of weather transmitters, allocation of frequencies for weather circuits, management of encryption of weather reports and unit management for line telegraphy of the weather service.