When the Germans invaded Russia, during World War II, the Germans began to use a new type of enciphered transmission between central headquarters and headquarters in the field. The transmissions were known as Fish at Bletchley Park. (See Lorenz cipher, Cryptanalysis of the Lorenz cipher.) The German army used Fish for communications between the highest authorities in Berlin and the high-ranking officials of the German Army in the field. The Fish traffic which the personnel at Bletchley Park intercepted, contained discussions, orders, situation reports and many more details about the intentions of the German Army. However, these transmissions were so challenging to decrypt that even with the assistance of the high speed Colossus computer, the messages could not be read until several days later. “Vital intelligence was obtained about Hitler’s intentions in the run up to D-Day 1944.”