Government Code & Cypher School Card Indexes

Vast quantities of information were obtained as a result of decoding Enigma & other enciphered signals. As each message was decoded and translated it was passed to the indexing team who identified the words and phrases to be indexed.

The intelligence was made useful by employing a wide range of different types of index. There were three basic types of Index: Indexes of key contents of messages; Indexes that facilitated translation and context; and Indexes that exploited the technical detail of the messages (transmission stations, time sent etc.).

GCHQ has released some of these Indexes to the Archives at Bletchley Park, and many more remain to be released. Examples currently kept at Bletchley Park include:

ABWEHR (German Military Intelligence) PERSONNEL (BALKANS) A-Z 3 boxes, ABWEHR PERSONNEL A-Z 6 boxes. A card for every personal name mentioned, each card with a reference number, a date and sometimes details of a report, actions, movements or notes.

ABWEHR W/T (Wireless Telegraphy) INDEX 4 boxes. Stations in W. Europe & Balkans, Spain & Portugal, invasion R Net agents in France, Norway & Denmark, Suedring stations. A card for each station lists reference number, date for intercept, a short note of content or type of message.

GERMAN EQUIPMENT & MANUFACTURERS 21 boxes. Classification is mainly by a reference code or manufacturer’s name. Each card contains the name of the piece of equipment, a brief description & a dated source.

JAPANESE INDEXES 6 boxes. Japanese Traffic Analysis Section Histories; Japanese Military Attaché Personal; Japanese alphabet flash cards; Order of Battle, Formation, Codename, Depots, Location; Japanese terms & glossaries; alphabetical index of Japanese fleet; alphabetical card index of Japanese words & phrases offering difficulty in translation & vocabulary.