Fish was the UK's GC&CS Bletchley Park codename for any of several German teleprinter stream ciphers used during World War II. Enciphered teleprinter traffic was used between German High Command and Army Group commanders in the field, so its intelligence value (Ultra) was of the highest strategic value to the Allies. This traffic normally passed over landlines, but as German forces extended their geographic reach beyond western Europe, they had to resort to wireless transmission.
German prisoners prepare the "Russian Fish" for loading and shipment to England.
The Lorenz SZ42 machine with its covers removed. Bletchley Park museum
Bletchley Park is an English country house and estate in Bletchley, Milton Keynes (Buckinghamshire), that became the principal centre of Allied code-breaking during the Second World War. The mansion was constructed during the years following 1883 for the financier and politician Herbert Leon in the Victorian Gothic, Tudor and Dutch Baroque styles, on the site of older buildings of the same name.
The mansion in 2017
Stephen Kettle's 2007 Alan Turing statue
Hut 1
Hut 4, adjacent to the mansion, is now a bar and restaurant for the museum.