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: a German naval report covering all areas, for May 13; that the 4th Air Fleet's battle headquarters are at Kharkov, from May 1; and that the 8th Air Corps is bringing up rear units to support the threatened front at Kharkov, on May 14.