Admiralty: Operational Intelligence Centre: Intelligence from Intercepted German, Italian and Japanese Radio Communications, WWII

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Details of DEFE 3
Reference:DEFE 3
Admiralty: Operational Intelligence Centre: Intelligence from Intercepted German, Italian and Japanese Radio Communications, WWII

File copies of teleprinter messages. The various series of messages are of two distinct types: intercepted signals, decrypted, translated, and sent from the German Naval Section of the Admiralty's Naval Intelligence Division at Bletchley Park to the division's Operational Intelligence Centre in the Admiralty; and summaries of intelligence derived from such signals sent to the War Office, Air Ministry and overseas commands. These signals became known as ULTRA.

PLEASE NOTE: Records within this series are available to download free of charge as part of the Digital Microfilm project.

Date: 1941-1945

The files were bound in order of the German time of origin (in some cases upwards from the bottom of the file), irrespective of the time and date of decrypting, the cipher employed (which is rarely indicated), or the area, type of vessel, or significance of the signal. The copies that compose this series follow the same arrangement.

Related Material: Records about the administrative arrangements for Hut 3 at Bletchley Park can be found in the Hut 3 directives (pieces 126-127 include appreciations of work on ULTRA by senior military commanders, including Eisenhower) in::
Records relating to signals intelligence passed to the Prime Minister from the Government Code and Cypher School during the Second World War are in HW 1
Summaries of tactical signals intelligence forwarded to allied commands by the Government Code and Cypher School are in HW 20
Reports are in PRO 31/20
HW 3/124
HW 3/125
HW 3/126
HW 3/127
The station and allied forces codes for transmission of material decoded are contained in HW 3/165
Another file of ULTRA material, relating to the sinking of the SCHARNHORST along with reports of the ULTRA Representatives with US Army Groups is in ADM 223/36
Held by: The National Archives, Kew
Legal status: Public Record(s)
Language: English
Creator: Admiralty Naval Intelligence Division, 1945-1964
Physical description: 1021 files, microform and volumes
Access conditions: Available in digital format unless otherwise stated
Immediate source of acquisition: from 1977 Ministry of Defence
Accruals: Series is accruing.
Publication note: For further information read Code Breakers: the Inside Story of Bletchley Park ed FH Hinsley and Alan Stripp, Oxford University Press, 1993. Patrick Beesley Very Special Intelligence:The Story of the Admiralty's Operational Intelligence Centre 1939-1945 (London, 1977)
Administrative / biographical background:

During the war of 1939-1945, radio messages transmitted by the German, Italian and Japanese armed forces were, whenever possible ciphered, intercepted by allied radio operators. Ciphered messages intercepted by British radio stations were decrypted at the Government Code and Cipher School at Bletchley Park in Buckinghamshire ('B.P' or 'Station X'), and then sent to the intelligence staffs of operational forces at home and overseas.

The German armed forces made extensive use of an electrical keyboard (the Enigma machine) which produced an extremely complex and easily varied means of enciphering and deciphering signals; the system was thought to be secure for all practical purposes, and was in constant use for important communications throughout the war. Bletchley Park, however had an Enigma machine acquired just before the war, and further machines with current settings were captured from time to time. With the aid of these and of computers which they were developing independently, the British cryptanalysts were able to read a high proportion of enemy signals enciphered in this way. In order to preserve the secret that the cipher could be broken, intelligence derived from Enigma signals was given a special security classification, MSS (Most Secret Source) or Ultra, and disguised as having come from agents in enemy territory, or from prisoners of war.

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