Catalogue description Government Code and Cypher School: Naval Section: Reports, Working Aids and Correspondence

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Details of HW 8
Reference: HW 8
Title: Government Code and Cypher School: Naval Section: Reports, Working Aids and Correspondence

This series consists of correspondence, minutes, memoranda, instructions, information bulletins and other papers relating to the organisation of Naval Section, its operations and functions, relations with the Admiralty and with stations responsible for the interception of enemy communications, and with its American counter-part, OP-20-G, Washington. The main intelligence feed from Naval Section to the Admiralty was immediate reporting by teleprinter, and these records, and related Admiralty teleprinter messages have been destroyed.

Also included in this series are histories of some aspects of the work carried out by Naval Section, as well as histories of the main interception stations and of other specialist interception efforts ashore and afloat.

Other related records in this division include the Section's intelligence reports in HW 18 and HW 23. The official histories of the naval war, as reported by signals intelligence, are in HW 11, and Naval Section historical memoranda and other items can be found in HW 3.

Date: 1914-1946
Related material:

Papers of the Far East Combined Bureau are in HW 4

Held by: The National Archives, Kew
Legal status: Public Record(s)
Language: English

Government Code and Cypher School, Naval Section, 1924-1946

Physical description: 158 bundles, files and volumes
Access conditions: Open
Immediate source of acquisition:

In 1995-2009 Government Communications Headquarters

Accruals: No further accruals expected
Administrative / biographical background:

The origins of the Naval Section of the Government Code and Cypher School lie in the 1920s, when the Admiralty took an interest in the development of the Japanese navy. The work of the Section remained low-key until 1934, when intensive effort on European targets began with the breaking of the Italian Naval code at a time when the belligerence of Italian foreign policy was a cause for concern. No interest was taken in German naval traffic until 1936, when numerous German naval transmissions using the ENIGMA machine cypher were intercepted. These messages remained unbroken at the time. Unable to break into the code, the Section had recourse instead to external analysis of wireless communications to derive intelligence from them (known as 'W/T I'). In August 1939 the German W/T I sub-section was transferred from GC&CS to the Naval Intelligence Division of the Admiralty.

As a result of this action, when Frank Birch, veteran of naval code breaking in Room 40 during the First World War was recalled to Bletchley Park in September 1939, he found that the German naval sub-section consisted himself and two other members of staff. The section soon expanded dramatically, taking over again the W/T I work previously transferred to the Admiralty, breaking the German naval ENIGMA code, and employing huge numbers of cryptographers, analysts and reporters to process the intercepted communications and supply intelligence to the British and Allied Commands.

Birch, who along with Nobby Clarke (head of the Naval Section from 1939 until mid-1941) had written the war history of the operations of Room 40 after the First World War (see HW 7) assiduously collected written material relating to the work of the Naval Section to provide a war record, and this is included among the Naval Section headquarters correspondence in this series.

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