Yugoslavia and The Allies - British Intelligence Sources

British Intelligence Sources

Most of the Signals intelligence obtained by Bletchley Park on the Balkans was initially from Luftwaffe morse code traffic encoded by Enigma; initially the general Luftwaffe Red key, then various German Army keys. They also decrypted various teleprinter links for high-level traffic: Fish (Vienna-Athens) then Codfish (Straussberg-Salonika), plus medium and low grade hand cyphers. For German policy on Yugoslavia, communications to Tokyo from the Japanese Ambassador, General Oshima Hiroshi, were also useful. With the primitive communications infrastructure and the disruption of land communications, the German forces in Yugoslavia relied heavily on radio communications which, unknown to themselves was insecure, so that a 1945 comment was that "never in the field of Signals intelligence has so much been decrypted about so little."

While the volume of messages was not great, Bletchley Park also intercepted messages from Tito and from the separate Slovene Communist Party to Georgi Dimitrov, the Secretary-General of the Comintern in Moscow. These messages to Dimitrov continued even after the Comintern was officially dissolved in June 1943.

The volume of Enigma decrypts from the Soviet Fronts and the Balkans declined substantially from the summer of 1944, but this was more than offset for the Soviet Fronts by success with Fish links.