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 correspondence: an amplified copy of a report sent on September 10 noting that the Soviet armed forces were putting up fierce resistance, but had lost some 8,000 aircraft; that the German army marching on Kharkov would probably reach the Caucasus within a few days; and that the Volga area was anticipated as the last line of Soviet resistance in Europe, but was weak because of previous heavy losses.