0309

File Title 'C', Chief of the Secret Intelligence Service (SIS): Reports and Information; Blue Jackets (BJs)
Reference FO 1093/309
Date 26 December 1939 - 8 December 1942
Government Department Foreign Office
File Accession Date 23 May 2013

Description

A file of correspondence, memoranda, and intercepted signals concerning cyphers, signal interception, and leakage of information during the Second World War. Subjects discussed in this file include measures to preserve the secrecy and security of intelligence from intercepted communications, including limiting circulation and adding further levels of security clearance; the sharing of signals intelligence with relevant government departments, and the types of intelligence in which these departments were interested; leakages of Allied information detected in intercepted Japanese diplomatic telegrams, including rumoured Allied war plans in the Pacific; the obtainment by the Japanese of the text of a secret Foreign Office telegram; intercepted Japanese reports of Royal Navy forces in Bombay; Japanese reports of a rumoured German-Soviet peace, resulting from a breach of security by a British diplomatic official; false intelligence fed to Japanese embassies to sow confusion; and a report of the breaking of a German diplomatic code.

Document Title Date
i Front Cover Download PDF (445 KB)
1st 'C', Chief of the Secret Intelligence Service (SIS): Reports and Information; Blue Jackets (BJs) Download PDF (110.80 MB)
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