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Chapter I

Organization and Working of German Naval Communications Intelligence


  1. In relation to German naval organization.
  2. Subdivision of 4 SKL "Marinenachrichtendienst," naval communication service.
  3. 4 SKL/III "Funkaufklärung" (radio intelligence).
  4. The German radio intelligence bulletin and the handling of ULTRA.
  5. Concentration of German communication intelligence on Allied convoy traffic.
  6. Use of non-radio intelligence material.

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  1. In relation to German naval organization.
  2. The German naval intercept service and related intelligence activities formed part of the division of Naval Communications, which in turn formed one of the six numbered "Naval War Staffs." Late in 1944 these war staffs were as follows:

    OKM Naval High Command Grand Admiral Dönitz
    Stabschef SKL Vice Chief of Naval Staff Vice Admiral Meisel
    1 SKL Operations Rear Admiral Hans Mayer
    2 SKL/BdUop U-boat Operations Rear Admiral Godt1
    3 SKL Intelligence Rear Admiral Otto Schulz
    4 SKL Communications Rear Admiral Stummel
    5 SKL Radar Research Commander Meckel
    6 SKL Hydrography & Meteorology Vice Admiral Fein

  3. Subdivision of 4 SKL "Marinenachrichtendienst," naval communication service.
  4. Chef MND: Rear Admiral Stummel

    1. Central Office: Captain Möller.
    2. German Communications: Captain Lucan
    3. Radio communications, stations, frequencies, etc.
      Naval codes and ciphers. Security.
      Recognition signals.

    4. Radio Intelligence: Captain Kupfer
    5. Intercept, traffic analysis, low-grade recoveries.

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    1. Radar: This section was formed in August 1943, in an attempt to combat Allied location of U-boats and included research on Allied non-radar location devices as well as radar. Special effort went into construction of search receiving equipment.
    2. Location: After bombardment of Berlin in November 1943, Section I moved to Koralle with Dönitz and staff. Sections II and III moved to Bismark and later to Eberswaldo. When the Russians reached the Oder in 1945, 4 SKL moved to Wilhelmshaven area. (Ultra/ZIP/ZG/337)

  1. 4 SKL/III "Funkaufklärung" (radio intelligence).
    1. Intercept net.
    2. The intercept net was organized, in part at least, into naval D/F divisions (MPA), naval D/F main stations (MPHS), and naval D/F subsidiary stations (MPNS). Before the loss of Italy the German navy probably maintained about 50 intercept stations covering the Black Sea, Mediterranean, Baltic, Arctic, and Atlantic waters. Emphasis in the case of Atlantic stations was of course on British naval and RAF traffic, including radio traffic. Of particular interest was MPA Flanders, located in the Castle of Saint Andries near Bruges, where the operators captured from U-664 (Graef) were trained.2

      In addition to interception, D/F work and the training of B-Dienst operators, MPA Flanders received and broke low to medium grade British naval traffic, such as Loxo and Foxo. Some of the other principal outlying stations performed similar intelligence duties, and issued routine summaries for their respective areas. B-groups were also maintained on various command staffs in occupied territory, to whom were sent daily recoveries of delivery groups and lettered coordinates for English position reporting system.

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    1. Headquarters of 4 SKL/III.
    2. All high grade naval traffic was forwarded to 4 SKL/III in Germany, together with D/F's, traffic analysis, and low-grade decoding results. The home station was organized into two sections, according to the Japanese Naval Attache: "Auswertung" (Evaluation) and cryptanalysis. The number of workers was said to be 800 in the early part of 1944, but it is not clear whether this figure applied to both sections or cryptanalysis alone.

      1. "Auswertung" (Evaluation).
      2. The full extent of this section's functions is not at present known but its various subdivisions covered the following activities:

        • Intercept of enemy traffic.
        • Reconstruction of letter coordinates (from position reporting systems such as SP 02274).
        • Recovery of delivery groups. (Ultra/ZIP/ZG/3 10)

        The above duties suggest that the evaluation section was responsible for D/F correlation and traffic analysis in general.

      3. Cryptanalysis.
      4. The internal organization and workings of this section are as yet little known. After the armistice with Italy, officers of the Italian naval communications intelligence organization (SIS), informed the Allies that they had worked in close collaboration with the Germans, and yet the Italians had never found out much about the inside of the German organization. Rome and Berlin had exchanged technical information and captured cryptographic documents, Rome, however, in the role of a subordinate. Neither maintained a permanent liaison with the other, although visits were exchanged. (GC&CS Intel Memo #66)

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  1. The German radio intelligence bulletin and the handling of ULTRA.3
  2. A German naval radio intelligence bulletin, dated 23 June 1944, was captured in Italy in September 1944. A weekly publication, this bulletin offered the most complete cross section ever seen here of 4 SKL/III's work. Just what section of 4 SKL/III compiled it is not clear, but it contains a large amount of material that would probably come from the "Auswertung" section. Presumably a correlation room existed, to which were passed the final results of the entire communications intelligence organization. The bulletin is carefully organized and apparently follows a relatively fixed form.

    1. Distribution of the bulletin.
    2. According to the introductory printed pages, 25 copies of the bulletin were made, 22 of which were distributed and 3 held in reserve. This distribution list is considerably longer than is customary in the case of U.S. Navy radio intelligence bulletins.

      Distribution outside of Naval High Command (8 copies):

      • Naval Group Command West, Staff (located at Paris and in charge of naval surface units based on Biscay and Channel ports as well as coastal defense and Channel convoys).
      • Battle Group (Task group Tirpitz and 4th Destroyer Flotilla in northern Norway)
      • Comsubs Norway/Admiral Northern Waters at Narvik
      • Naval Liaison with Werhmacht Field Headquarters
      • German Naval Command Italy

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      • 10th Flieger Corps via Air Fleet 3 (West Europe)
      • GAF Lofoten (the part of the Luftwaffe responsible for reconnaissance on Arctic convoys for Russia)
      • Small Battle Units Command (set up early in 1944, in charge of midget submarines, explosive motor boats, special commandos for mining and sabotage)

      Distribution within Naval High Command:

      • 6 copies to various sections of COMINCH and CNO including U-boat operational command (i.e. Chief of SKL, 1 SKL section, 2 SKL/BdU op)
      • 4 copies to ONI (3 SKL)
      • 1 copy to radar and electronics research (5 SKL)
      • 3 copies within 4 SKL itself including one to the DNC

    1. Grades of radio intelligence information and its dissemination by dispatch.
    2. Two kinds of radio intelligence information are distinguished according to their source:

      • "B-Reports" or "B-Information": based on traffic analysis and reading of open or encoded messages.
      • "X-B-Reports" or "X-B-Information": based on the decryption of high grade traffic.

      The captured bulletin contained both "B" and "X-B", the latter being distinguished from the former by framing or boxing in heavy black lines. To avoid any uncertainty which might arise in the interpretation of the information presented in the bulletin a standard form is indicated for degrees of reliability. Any unqualified statement could be taken as certain on the part of the reader. It should be noted, however, that this highest degree of reliability could apply to a good D/F fix as

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      well as to a decrypted statement. "Probably" or "approximately" and "presume" or "presumably" qualified the lesser degrees of reliability in that order. In addition to the bulletin, "X-B situation reports" were issued daily by radio. No examples of these have been seen here. GC&CS describes them as daily summaries, sent out over the signature of the radio intelligence organization, which contain information from all intelligence sources, but mainly from the B-service itself. (ZIP/ZG/233, p. 1)

      In addition to the above standard dissemination, radio intelligence material of an urgent operational nature might be sent by dispatch provided it was properly paraphrased and made no reference to source. This practice was to be limited to the most exceptional circumstances, particularly in the case of "X-B" information, for, as pointed out by the bulletin's printed introduction: "Should the enemy learn that X-B reports are obtained by the deciphering of his radio messages," he would destroy the work of months - even years - by changing his cipher data, and thus one of the most important sources of information for the execution of the naval war would be destroyed. Had the German navy observed these instructions more carefully, it might have been impossible for the Atlantic Section to demonstrate the existence and source of "X-B" information.

    1. Captured bulletin's information, its organization and scope.
    2. If the captured copy of the 23 June 1944 issue is a fair sample, the German naval radio intelligence bulletin shows the advantage which comes from centralizing the correlation of all interception results. (The captured bulletin covers the period from 12-18 June) It includes studies on topics of current operational interest such as the reconstruction of Atlantic convoy cycles as well as charts showing locations of contacts and attacks reported by Allied units.

      At the request of OP-20-G, U.S. Navy Communications Security section (OP-20-X) examined the document but found "no evidence that U.S. cryptographic systems have been successfully attacked." Other than the monitoring of BAMS circuits, German attention was concentrated on British naval circuits, most of which had been subjected to close analysis. Although the information on US-Gibraltar convoys was as

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      accurate as far as it went, it was not classified by the Germans as "X-B." Information on US-UK convoys, however, was in part classified as "X-B." No report has been received from the British on the sources of the German information given in the bulletin but these sources would presumably be described as "low-grade."

  1. Concentration of German communication intelligence on Allied convoy traffic.
  2. The captured bulletin tends to confirm the natural supposition that the German navy's communication intelligence organization would concentrate its energies on serving the most important operational part of the navy, the U-boat, and thus would specialize in Allied convoy traffic. That the enemy was adept at exploiting all sources in arriving at a clear and current picture of the convoy situation was shown many times in U-boat traffic. There were exceptions, but on the whole German radio intelligence did furnish the U-boat navy with that essential requisite for the successful prosecution of the U-boat war: good convoy intelligence.

    The stereotyped nature of convoy traffic may have simplified the German problem so that analysis and delivery group recoveries would suffice to keep the convoy chart well posted and up to date. Against this background, however, they were able at times to read actual convoy messages in combined cipher and thus clarify and correct their plots as well as accumulate invaluable knowledge of convoy habits and procedures.

  3. Use of non-radio intelligence material.
  4. It will be noted that four copies were routed to 3 SKL (German Naval Intelligence) and that the daily "X-B" situation report drew on non-communication sources. The captured bulletin of 23 June, however, contains little that can be traced directly to outside sources except for the use of agents' reports in connection with Gibraltar convoys. The extent to which German radio intelligence organization was itself responsible for the correlation of its own material with that from non-radio intelligence sources is not known. The fact remains that it undoubtedly furnished the most important intelligence for U-boat Command. Before discussing German convoy intelligence,

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    it is necessary to review the kinds of information sent to U-boats at sea, with particular reference to the various sources, both radio intelligence and non-radio intelligence, which were acknowledged in U-boat traffic.

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Table of Contents
Next Chapter - Chapter II


1. Dönitz retained high command of the submarine force. Godt was the U-boat Command's staff officer for operations.

2. U-664 was sunk by a U.S. Navy aircraft on 9 August 1943. Eight crew members were lost and 44 captured.

3. These bulletins are on file at the National Archives, Washington, D.C. Records of the National Security Agency, "German Navy Reports on Intercepted Radio Messages (B./X.B. Berichte), 8 September 1939-23 March 1945," SRS-548, SRS-1166 and SRS-1870. Record Group 457, National Archives, Washington, D.C.

Transcribed and formatted for HTML by Rick Pitz, HyperWar Foundation