'C', Chief of the Secret Intelligence Service (SIS): Coordination of Wireless Interception and Cryptography

A file of correspondence and memoranda concerning communications interception and cryptography during the Second World War. The documents discuss the history of the wireless telegraphy board; the need for reorganisation due to the huge expansion of the board’s work during the course of the war; the staff needed after reorganisation, and the appointment of Admiral Somerville to command it; the exchange of information about cryptography with the American intelligence services; the fear that this might compromise sources of intelligence if too much information was disclosed; arrangements for the transportation of a group of American cryptographers over to Britain; the recruitment of Japanese-speaking personnel to help with decrypting Japanese signals; the security of Chinese codes and cyphers; and the decryption of German and Italian documents captured in Beirut.