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 reports on Germany: of Hitler's orders on aiming anti-aircraft guns, on May 20; of heavy German U-boat losses due to superior Allied equipment, with caution to be exercised, on May 23; that U-boats are to use anti-aircraft guns rather than submerge, on May 23; and that U-boat commanders are to stiffen their resolve, on May 21; on the Russian Front: of German Air Force (GAF) fighter pilots being asked to volunteer for service in the West, on May 25; and ZTPGM/19368 was sent to the Director of Naval Intelligence (DNI) (see 3456).