2497

File Title Government Code and Cypher School: Signals Intelligence Passed to the Prime Minister, Messages and Correspondence
Reference HW 1/2497
Date 25 February 1944
Government Department Government Code and Cypher School
File Accession Date 1993

Description

A file of signals intelligence reports, messages, and correspondence issued by the Government Code and Cypher School and sent by the head ('C') of the Secret Intelligence Service (MI6) to the Prime Minister, Winston Churchill. This file includes the following messages: that intelligence based on the analysis of patterns of Japanese naval communications (traffic analysis), not decodes, is to bear the codename THUMB; and extracts from signals sent by Washington to Colombo concerning Japanese naval forces in the Singapore area, based on traffic analysis, for the period of February 20-23.

Document Title Date
i Front Cover 25 February 1944 Download PDF (315 KB)
1st Government Code and Cypher School: Signals Intelligence Passed to the Prime Minister, Messages and Correspondence 25 February 1944 Download PDF (1.04 MB)
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