These were messages decoded in WWII by the Germans. Specifically the codebreaking department of the Supreme Command of the Armed Forces – OKW/Chi (Oberkommando der Wehrmacht/Chiffrier Abteilung).The codebreakers of OKW/Chi could solve most State Department cryptosystems, not only the low level ‘Gray’, ‘Brown’ but also the high level ‘A1’, ‘C1’ and the M-138-A strip cipher.
Unfortunately we don’t know the full story of their success with State Department systems.
Their main targets were the US embassies in European countries like Spain, Portugal, Sweden, Switzerland and the Soviet Union. However it seems they did not neglect to intercept and decode messages from around the globe.
Here are some interesting samples.Mrs Morgenthau’s trip to Moscow
Kabul government recognizes Syria and Lebanon as independent republics
Information on South African gold mines