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Guide reference: Military Records Information 26
Last updated: 7 October 2008

1. Why use this guide?

This guide will help you to find records relating to intelligence and security services held at The National Archives. It will give you

  • a general overview of the main sources
  • advice on how to find records using our catalogue
  • suggested record series to help you get started

The National Archives has records from the various military security and intelligence services as well as GCHQ, MI5 and (to a far lesser extent) MI6. This guide does not cover records from police agencies such as the Special Branch which are held in record series MEPO 38.

2. Essential information

Historically, intelligence has been gathered by individual branches of the military as well as centrally by the government security and intelligence agencies.  

Because of the sensitive nature of intelligence work, many files have been destroyed and others are retained in order to protect the identities of those involved in gathering intelligence.  

This is particularly true of files relating to the Special Operations Executive (during the Second World War) and MI5 and MI6.

3. War Office

3.1 Background

The War Office sections responsible for security and intelligence were the Directorate of Military Operations (DMO) and the Directorate of Military Intelligence (DMI).

DMO was responsible for outline operational planning up to the time when an operation Commander was appointed. It also collected information about British forces and the armed forces of close allies.

DMI was concerned with the armed forces of enemy countries, distant allies and neutral countries. It was in close touch with military attaches and missions abroad and was interested not only in military details but also in more general historical, topographical and economic information.

3.2 How to search for records

Records from the War Office have the departmental reference WO.

Use the Advanced search option in our catalogue with keywords such as 'Directorate Military Operations'.

3.3 Useful record series

The following record series are a good starting point for research in this area:

WO 208 - intelligence material including reports for the Second World War
WO 106 - military intelligence material to 1939
WO 78 - maps created as part of intelligence gathering operations
WO 157 - daily summaries of information and reports on military, economic and political affairs

4. Admiralty

4.1 Background

The Naval Intelligence Department (NID) provided much of the pre-First World War code-breaking expertise. The deciphering section formed in October 1914 was known as 'Room 40'.  

NID was concerned with all aspects of enemy and allied shipping including:

  • plotting shipping movements, particularly of enemy surface cruisers and submarines
  • collecting information on the topography of foreign countries, particularly coasts, and on coastal defences
  • signals intelligence work in both world wars

4.2 How to search for records

Records from the Admiralty have the departmental reference ADM.  

Use the Advanced search option in our catalogue with keywords such as 'naval intelligence'.   

4.3 Useful record series

The following record series are a good starting point for research in this area:

ADM 137 papers of NID in 'Room 40', many of them on signals intelligence
ADM 233 summaries of decrypted signals circulated by NID and the Government Code and Cypher School (GCCS); see also Signals Intelligence below
ADM 116 Cases Coding and Cyphering Committee. Use Advanced Search with keyword 'cypher' and under 'search within' enter ADM 116. Try other keywords in this series too
DEFE 3 translations of mainly German, Italian and Japanese decrypted signals and summaries of intelligence from signals
ADM 231 NID printed reports

5. Signals intelligence

5.1 Background

Air Intelligence gathered information on:

  • allied and enemy aircraft, their fuel systems and weaponry
  • enemy airfields
  • enemy bombing targets
  • effectiveness of allied bombing raids (using aerial reconnaissance)
  • enemy and allied air activity

Much intelligence was also gained from prisoners of war in enemy hands, either by coded letters or by interrogation after escapes.

5.2 How to search for records

Records from the Air Ministry have the departmental reference AIR.

Use the Advanced search option in our catalogue with relevant keywords. 

5.3 Useful record series

The following record series are a good starting point for research in this area:

AIR 1 contains scattered intelligence papers of the First World War
AIR 40 contains intelligence material including much on US Air Force operations and prisoners of war

6. Government Code and Cypher School and Government Communication Headquarters

6.1 Background

You will find a wealth of information about the formation and history of GCHQ and its predecessors as well as advice on related material in our catalogue (you will need to scroll down the page to see all sections).

6.2 How to find records

Records from the Government Code and Cypher School (GCCS) and Government Communication Headquarters (GCHQ) have the departmental reference HW.

Browse the records in HW or use the advanced search option in our catalogue with keywords such as:

  • code-breaking
  • cypher
  • Enigma
  • Bletchley Park
  • Bombe

7. Special Operations Executive (SOE)

7.1 Background

You will find useful information about the arrangement of the records and the history of the SOE in our catalogue (you will need to scroll down the page to see all sections).

Any personnel records that have survived are closed to the public until 2030 to protect the individuals concerned.

If you are interested in such a file and can demonstrate that the person it relates to is deceased, then you can submit a Freedom of Information request. If it relates to you personally you can make a request under Data Protection legislation using the leaflet on our website (scroll down the page to find it).

7.2 How to find records

Surviving records from the Special Operations Executive (SOE) have the departmental reference HS.

Records relating to SOE operations can also be found in the files of the Air Ministry (AIR), War Office (WO), Foreign Office (FO) and Prime Minister's Office (PREM).

Browse the records in HS or use the Advanced search option in our catalogue with keywords.

7.3 Useful record series

The following record series are a good starting point for research in this area:

KV 1 and KV 5 - MI5 investigations of several suspected renegade SOE agents
HS 11-20 SOE general file index cards which can list personal and biographical details of agents as well as references to the status of contacts known to be in enemy hands, safe houses, enemy intelligence officers, collaborators and traitors

8. Joint Intelligence Committee records

8.1 Background

The Joint Intelligence Committee (JIC), which still operates today, provides the Chiefs of Staff, Ministers and senior officials with intelligence assessments on security, defence and foreign affairs. The JIC also sets the priorities and co-ordinates the work of the separate intelligence services.

The JIC comprises of senior officials drawn from the Foreign Office, Ministry of Defence, Home Office, Department of Trade and Industry, Treasury and Cabinet Office, as well as the heads of the MI5, MI6 and GCHQ.

More information on the administrative history of the JIC is in our catalogue.

8.2 How to find records

Use the Advanced search option in our catalogue with keywords such as 'joint intelligence committee' or 'central intelligence'.

8.3 Useful record series

The following record series are a good starting point for research in this area:

CAB 158 JIC memoranda
CAB 159 JIC minutes

9. The Security Service (MI5) and the Secret Intelligence Service (MI6) records

9.1 Background

MI5 comes under the authority of the Home Secretary and is responsible for protecting the country against threats to national security, which include terrorism, espionage and the proliferation of weapons of mass destruction.

MI6 is an agency of the Foreign and Commonwealth Office and is responsible for gathering intelligence overseas.

Records from MI5 and MI6 are not made available to the public as freely as those from other departments - this is especially true for MI6 (or Secret Intelligence Service) files. 

The records are retained under section 3 (4) of the Public Records Act (1958) and Freedom of Information legislation does not apply to them.

The National Archives policy on selecting records from the security services gives more information.

You will find useful information about the arrangement of the records and the history of MI5 and the formation and history of MI6 in our catalogue (you will need to scroll down the page to see all sections).

9.2 How to search for records

MI5 records have the departmental reference KV. Records inherited by MI6 when it was created in 1909 have the departmental reference HD.

MI6 records are not open to the public, but reference is sometimes made to MI6 in files from other departments.

Browse the records in KV or HD or use the Advanced search option in our catalogue with keywords such as 'Secret Intelligence Service' or 'MI6'.

9.3 Useful record series

The following record series are a good starting point for research in this area

KV 4/185-196 - Second World War diaries of Captain Guy Liddell, head of MI5's B Division (counter-subversion)
HW1 - signals intelligence from GCHQ during the Second World War
FO 1093  - provides an illuminating source on the activities and funding of MI6
 

10. Defence Intelligence Staff records

10.1 Background

The Defence Intelligence Staff (DIS) records were created by the Ministry of Defence and have the departmental reference DEFE.  Prior to the establishment of the DIS, each branch of the military had its own intelligence service (see sections 3,4 and 5 of this guide).

MI5, MI6 and the GCHQ work alongside each other and come under the direction of the Joint Intelligence Committee (JIC). They also work alongside the Defence Intelligence Staff (DIS).

10.2 How to find records

Browse the records in DEFE by using the 'Browse catalogue' option on the search page or by entering DEFE in the search box on the same page.

Search our catalogue using keywords such as 'defence intelligence staff'. Refine your results using the options on the left of the search results page.

10.3 Useful record series

The following record series are a good starting point for research in this area

DEFE 21 and DEFE 44 - Scientific and technical intelligence
DEFE 31 - Defence Intelligence Staff, Secretariat
DEFE 62-64 - Intelligence Assessments, Reports and Studies
DEFE 65 - Intelligence Conferences, Committees and Working Parties
DEFE 27 - Defence Intelligence Staff Sub-Committee
DEFE 40 - papers of the Director of Scientific Intelligence, R V Jones
 

11. Records in other archives

British Library

The British Library has a collection of intelligence material such as maps, plans and gazetteers on India and SE Asia.
 

12. Further reading

12.1 Book list

Use our library catalogue to find a recommended book list.

The books are all available in The National Archives' reference library. You may also be able to find them in a local library. You can buy from a wide range of history titles in our bookshop.

12.2 Periodicals

 Intelligence and National Security

  • '100 Years of British Intelligence', Special Issue, Vol 27, Issue 1, 2012
  • 'Whitehall's Black Chamber: British Cryptology and the Government Code and Cypher School, 1919-1929', John Ferris, Vol 2 January 1987, pp.54-92
  • 'Declassification and Release Policies of the UK's Intelligence Agencies' and Sir Stephen Lander 'British Intelligence in the Twentieth Century', Vol. 17 No. 2, 2002, pp.7-32
     
Guide reference: Military Records Information 26

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