Bletchley Park in the context of "Enigma (2001 film)"

Government Communications Headquarters (GCHQ) is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the United Kingdom. Primarily based at The Doughnut in the suburbs of Cheltenham, GCHQ is the responsibility of the country's Secretary of State for Foreign and Commonwealth Affairs (Foreign Secretary), but it is not a part of the Foreign Office and its director ranks as a Permanent Secretary.

GCHQ was originally established after the First World War as the Government Code and Cypher School (GC&CS) and was known under that name until 1946. During the Second World War it was located at Bletchley Park, where it was responsible for breaking the German Enigma codes. There are two main components of GCHQ, the Composite Signals Organisation (CSO), which is responsible for gathering information, and the National Cyber Security Centre (NCSC), which is responsible for securing the UK's own communications. The Joint Technical Language Service (JTLS) is a small department and cross-government resource responsible for mainly technical language support and translation and interpreting services across government departments. It is co-located with GCHQ for administrative purposes.

The Lorenz SZ40, SZ42a and SZ42b were German rotor stream cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. The model name SZ is derived from Schlüssel-Zusatz, meaning cipher attachment. The instruments implemented a Vernam stream cipher.

British cryptanalysts, who referred to encrypted German teleprinter traffic as Fish, dubbed the machine and its traffic Tunny (meaning tunafish) and deduced its logical structure three years before they saw such a machine.

Alan Mathison Turing (/ˈtjʊərɪŋ/; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher and theoretical biologist. He was highly influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer. Turing is widely considered to be the father of theoretical computer science.

Born in London, Turing was raised in southern England. He graduated from King's College, Cambridge, and in 1938, earned a doctorate degree from Princeton University. During World War II, Turing worked for the Government Code and Cypher School at Bletchley Park, Britain's codebreaking centre that produced Ultra intelligence. He led Hut 8, the section responsible for German naval cryptanalysis. Turing devised techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for the Enigma machine. He played a crucial role in cracking intercepted messages that enabled the Allies to defeat the Axis powers in the Battle of the Atlantic and other engagements.

Doreen Edith Dominy Valiente (4 January 1922 – 1 September 1999) was an English Wiccan who was responsible for writing much of the early religious liturgy within the tradition of Gardnerian Wicca. An author and poet, she also published five books dealing with Wicca and related esoteric subjects.

Born to a middle-class family in Surrey, Valiente began practising magic while a teenager. Working as a translator at Bletchley Park during the Second World War, she also married twice in this period. Developing her interest in occultism after the war, she began practising ceremonial magic with a friend while living in Bournemouth. Learning of Wicca, in 1953 she was initiated into the Gardnerian tradition by its founder, Gerald Gardner. Soon becoming the High Priestess of Gardner's Bricket Wood coven, she helped him to produce or adapt many important scriptural texts for Wicca, such as The Witches Rune and the Charge of the Goddess, which were incorporated into the early Gardnerian Book of Shadows. In 1957, a schism resulted in Valiente and her followers leaving Gardner in order to form their own short-lived coven. After investigating the Wiccan tradition of Charles Cardell, she was initiated into Raymond Howard's Coven of Atho in 1963. She went on the following year to work with Robert Cochrane in his coven, the Clan of Tubal Cain, although she later broke from this group.

In 1941 when the Axis invaded Yugoslavia, King Peter II formed a Government in exile in London, and in January 1942 the royalist Draža Mihailović became the Minister of War with British backing. But by June or July 1943, British Prime Minister Winston Churchill had decided to withdraw support from Mihailović and the Chetniks he led, and support the Partisans headed by Josip Broz Tito, even though this would result in "complete communist control of Serbia". The main reason for the change was not the reports by Fitzroy Maclean or William Deakin, or as later alleged the influence of James Klugmann in Special Operations Executive (SOE) headquarters in Cairo or even Randolph Churchill, but the evidence of Ultra decrypts from the Government Code and Cipher School in Bletchley Park that Tito's Partisans were a "much more effective and reliable ally in the war against Germany". Nor was it due to claims that the Chetniks were collaborating with the enemy, though there was some evidence from decrypts of collaboration with Italian and sometimes German forces.

The Battle of Cape Matapan (Greek: Ναυμαχία του Ταινάρου) was a naval battle during the Second World War between the Allies, represented by the navies of the United Kingdom and Australia, and the Royal Italian Navy, from 27 to 29 March 1941. Cape Matapan is on the south-western coast of the Peloponnesian peninsula of Greece.

After the interception and decryption of Italian signals by the Government Code and Cypher School (GC&CS) at Bletchley Park (the decrypted intelligence codenamed Ultra), ships of the Royal Navy and Royal Australian Navy, under the command of Admiral Sir Andrew Cunningham, intercepted and sank or severely damaged several ships of the Italian Regia Marina under Squadron-Vice-Admiral Angelo Iachino. The opening actions of the battle are also known in Italy as the Battle of Gaudo.

Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is regarded as the world's first programmable, electronic, digital computer (the first electromechanical being Konrad Zuse's Z3 completed in Berlin in 1941), although it was programmed by switches and plugs and not by a stored program.

Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers based on plans developed by mathematician Max Newman at the Government Code and Cypher School at Bletchley Park.

The cyclometer was a cryptologic device designed, "probably in 1934 or 1935," by Marian Rejewski of the Polish Cipher Bureau's German section (BS-4), to catalog the cycle structure of Enigma permutations, thereby facilitating the decryption of German Enigma ciphertext.

With Rejewski's later cryptologic bomb, it can be viewed as a predecessor to the Bombe that was to help break Enigma ciphers later in the war at Bletchley Park in England.