Ultra was the designation adopted by British military intelligence in June 1941 for wartime signals intelligence obtained by breaking high-level encrypted enemy radio and teleprinter communications at the Government Code and Cypher School (GC&CS) at Bletchley Park.Ultra eventually became the standard designation among the western Allies for all such intelligence. The name arose because the intelligence thus obtained was considered more important than that designated by the highest British security classification then used (Most Secret) and so was regarded as being Ultra secret. Several other cryptonyms had been used for such intelligence.
The United Kingdom, officially the United Kingdom of Great Britain and Northern Ireland but more commonly known as the UK or Britain, is a sovereign country lying off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.
Military intelligence is a military discipline that uses information collection and analysis approaches to provide guidance and direction to assist commanders in their decisions. This aim is achieved by providing an assessment of data from a range of sources, directed towards the commanders' mission requirements or responding to questions as part of operational or campaign planning. To provide an analysis, the commander's information requirements are first identified, which are then incorporated into intelligence collection, analysis, and dissemination.
Signals intelligence (SIGINT) is intelligence-gathering by interception of signals, whether communications between people or from electronic signals not directly used in communication. Signals intelligence is a subset of intelligence collection management.
The code name Boniface was used as a cover name for Ultra. In order to ensure that the successful code-breaking did not become apparent to the Germans, British intelligence created a fictional MI6 master spy, Boniface, who controlled a fictional series of agents throughout Germany. Information obtained through code-breaking was often attributed to the human intelligence from the Boniface network.The U.S. used the codename Magic for its decrypts from Japanese sources including the so-called "Purple" cipher.
Magic was an Allied cryptanalysis project during World War II. It involved the United States Army's Signals Intelligence Service (SIS) and the United States Navy's Communication Special Unit.
Much of the German cipher traffic was encrypted on the Enigma machine. Used properly, the German military Enigma would have been virtually unbreakable; in practice, shortcomings in operation allowed it to be broken. The term "Ultra" has often been used almost synonymously with "Enigma decrypts". However, Ultra also encompassed decrypts of the German Lorenz SZ 40/42 machines that were used by the German High Command, and the Hagelin machine.
Nazi Germany is the common English name for Germany between 1933 and 1945, when Adolf Hitler and his Nazi Party (NSDAP) controlled the country through a dictatorship. Under Hitler's rule, Germany was transformed into a totalitarian state that controlled nearly all aspects of life via the Gleichschaltung legal process. The official name of the state was Deutsches Reich until 1943 and Großdeutsches Reich from 1943 to 1945. Nazi Germany is also known as the Third Reich, meaning "Third Realm" or "Third Empire", the first two being the Holy Roman Empire (800–1806) and the German Empire (1871–1918). The Nazi regime ended after the Allies defeated Germany in May 1945, ending World War II in Europe.
The Enigma machines are a series of electro-mechanical rotor cipher machines, mainly developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. Enigma was invented by the German engineer Arthur Scherbius at the end of World War I. Early models were used commercially from the early 1920s, and adopted by military and government services of several countries, most notably Nazi Germany before and during World War II. Several different Enigma models were produced, but the German military models, having a plugboard, were the most complex. Japanese and Italian models were also in use.
Cryptanalysis of the Enigma ciphering system enabled the western Allies in World War II to read substantial amounts of Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio and teleprinter transmissions, was given the codename Ultra. This was considered by western Supreme Allied Commander Dwight D. Eisenhower to have been "decisive" to the Allied victory.
Many observers, at the time and later, regarded Ultra as immensely valuable to the Allies. Winston Churchill was reported to have told King George VI, when presenting to him Stewart Menzies (head of the Secret Intelligence Service and the person who controlled distribution of Ultra decrypts to the government): "It is thanks to the secret weapon of General Menzies, put into use on all the fronts, that we won the war!"F. W. Winterbotham quoted the western Supreme Allied Commander, Dwight D. Eisenhower, at war's end describing Ultra as having been "decisive" to Allied victory. Sir Harry Hinsley, Bletchley Park veteran and official historian of British Intelligence in World War II, made a similar assessment of Ultra, saying that while the Allies would have won the war without it, "the war would have been something like two years longer, perhaps three years longer, possibly four years longer than it was." However, Hinsley and others have emphasized the difficulties of counterfactual history in attempting such conclusions, and some historians have said the shortening might have been as little as the three months it took the United States to deploy the atomic bomb.
Sir Winston Leonard Spencer-Churchill, was a British politician, army officer, and writer. He was Prime Minister of the United Kingdom from 1940 to 1945, when he led Britain to victory in the Second World War, and again from 1951 to 1955. Churchill represented five constituencies during his career as a Member of Parliament (MP). Ideologically an economic liberal and imperialist, for most of his career he was a member of the Conservative Party, which he led from 1940 to 1955, but from 1904 to 1924 was instead a member of the Liberal Party.
Major General Sir Stewart Graham Menzies, was Chief of MI6, the British Secret Intelligence Service (SIS), from 1939 to 1952, during and after the Second World War.
The Secret Intelligence Service (SIS), commonly known as MI6, is the foreign intelligence service of the government of the United Kingdom, tasked mainly with the covert overseas collection and analysis of human intelligence (HUMINT) in support of the UK's national security. SIS is a member of the country's intelligence community and its Chief is accountable to the country's Foreign Secretary.
The existence of Ultra was kept secret for many years after the war. After it was revealed in the middle 1970s, historians have altered the historiography of World War II. For example, Andrew Roberts, writing in the 21st century, states, "Because he had the invaluable advantage of being able to read [General Erwin] Rommel's Enigma communications, [Field Marshall Bernard] Montgomery knew how short the Germans were of men, ammunition, food and above all fuel. When he put Rommel's picture up in his caravan he wanted to be seen to be almost reading his opponent's mind. In fact he was reading his mail."Over time, Ultra has become embedded in the public consciousness and Bletchley Park has become a significant visitor attraction. As stated by historian Thomas Haigh, "The British code-breaking effort of the Second World War, formerly secret, is now one of the most celebrated aspects of modern British history, an inspiring story in which a free society mobilized its intellectual resources against a terrible enemy."
Most Ultra intelligence was derived from reading radio messages that had been encrypted with cipher machines, complemented by material from radio communications using traffic analysis and direction finding. In the early phases of the war, particularly during the eight-month Phoney War, the Germans could transmit most of their messages using land lines and so had no need to use radio. This meant that those at Bletchley Park had some time to build up experience of collecting and starting to decrypt messages on the various radio networks. German Enigma messages were the main source, with those of the Luftwaffe predominating, as they used radio more and their operators were particularly ill-disciplined.
Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication, which can be performed even when the messages are encrypted. In general, the greater the number of messages observed, or even intercepted and stored, the more can be inferred from the traffic. Traffic analysis can be performed in the context of military intelligence, counter-intelligence, or pattern-of-life analysis, and is a concern in computer security.
Direction finding (DF), or radio direction finding (RDF), is the measurement of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication, including radar signals detection and monitoring (ELINT/ESM). By combining the direction information from two or more suitably spaced receivers, the source of a transmission may be located via triangulation. Radio direction finding is used in the navigation of ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. RDF was important in combating German threats during both the World War II Battle of Britain and the long running Battle of the Atlantic. In the former, the Air Ministry also used RDF to locate its own fighter groups and vector them to detected German raids.
The Phoney War was an eight-month period at the start of World War II, during which there was only one limited military land operation on the Western Front, when French troops invaded Germany's Saar district. The Phoney period began with the declaration of war by the United Kingdom and France against Nazi Germany on 3 September 1939, and ended with the German attack on France and the Low Countries on 10 May 1940. While there was no large-scale military action by Britain and France, they did begin economic warfare, and shut down German surface raiders. They created elaborate plans for numerous large-scale operations designed to swiftly and decisively cripple the German war effort. These included opening a French-British front in the Balkans; invading Norway to seize control of Germany's main source of iron ore; and a strike against the Soviet Union, to cut off its supply of oil to Germany. Only the Norway plan came to fruition, and it was too little too late in April 1940.
"Enigma" refers to a family of electro-mechanical rotor cipher machines. These produced a polyalphabetic substitution cipher and were widely thought to be unbreakable in the 1920s, when a variant of the commercial Model D was first used by the Reichswehr. The German Army, Navy, Air Force, Nazi party, Gestapo and German diplomats used Enigma machines in several variants. Abwehr (German military intelligence) used a four-rotor machine without a plugboard and Naval Enigma used different key management from that of the army or air force, making its traffic far more difficult to cryptanalyse; each variant required different cryptanalytic treatment. The commercial versions were not as secure and Dilly Knox of GC&CS, is said to have broken one before the war.
German military Enigma was first broken in December 1932 by the Polish Cipher Bureau, using a combination of brilliant mathematics, the services of a spy in the German office responsible for administering encrypted communications, and good luck.The Poles read Enigma to the outbreak of World War II and beyond, in France. At the turn of 1939, the Germans made the systems ten times more complex, which required a tenfold increase in Polish decryption equipment, which they could not meet. On 25 July 1939, the Polish Cipher Bureau handed reconstructed Enigma machines and their techniques for decrypting ciphers to the French and British. Gordon Welchman wrote,
Ultra would never have got off the ground if we had not learned from the Poles, in the nick of time, the details both of the German military Enigma machine, and of the operating procedures that were in use.
At Bletchley Park, some of the key people responsible for success against Enigma included mathematicians Alan Turing and Hugh Alexander and, at the British Tabulating Machine Company, chief engineer Harold Keen.After the war, interrogation of German cryptographic personnel, led to the conclusion that German cryptanalysts understood that cryptanalytic attacks against Enigma were possible but were thought to require impracticable amounts of effort and investment. The Poles' early start at breaking Enigma and the continuity of their success, gave the Allies an advantage when World War II began.
In June 1941, the Germans started to introduce on-line stream cipher teleprinter systems for strategic point-to-point radio links, to which the British gave the code-name Fish.Several systems were used, principally the Lorenz SZ 40/42 (Tunny) and Geheimfernschreiber (Sturgeon). These cipher systems were cryptanalysed, particularly Tunny, which the British thoroughly penetrated. It was eventually attacked using Colossus, which were the first digital programme-controlled electronic computers. In many respects the Tunny work was more difficult than for the Enigma, since the British codebreakers had no knowledge of the machine producing it and no head-start such as that the Poles had given them against Enigma.
Although the volume of intelligence derived from this system was much smaller than that from Enigma, its importance was often far higher because it produced primarily high-level, strategic intelligence that was sent between Wehrmacht High Command (OKW). The eventual bulk decryption of Lorenz-enciphered messages contributed significantly, and perhaps decisively, to the defeat of Nazi Germany.Nevertheless, the Tunny story has become much less well known among the public than the Enigma one. At Bletchley Park, some of the key people responsible for success in the Tunny effort included mathematicians W. T. "Bill" Tutte and Max Newman and electrical engineer Tommy Flowers.
In June 1940, the Italians were using book codes for most of their military messages, except for the Italian Navy which, in early 1941 had started using a version of the Hagelin rotor-based cipher machine C-38.This was broken from June 1941 onwards by the Italian subsection of GC&CS at Bletchley Park.
In the Pacific theatre, a Japanese cipher machine, called "Purple" by the Americans, was used for highest-level Japanese diplomatic traffic. It produced a polyalphabetic substitution cipher, but unlike Enigma, was not a rotor machine, being built around electrical stepping switches. It was broken by the US Army Signal Intelligence Service and disseminated as Magic . Detailed reports by the Japanese ambassador to Germany were encrypted on the Purple machine. His reports included reviews of German assessments of the military situation, reviews of strategy and intentions, reports on direct inspections by the ambassador (in one case, of Normandy beach defences), and reports of long interviews with Hitler.
The chief fleet communications code system used by the Imperial Japanese Navy was called JN-25 by the Americans and by early 1942, they had made considerable progress in decrypting Japanese naval messages. The Japanese are said to have obtained an Enigma machine in 1937, although it is debated whether they were given it by the Germans or bought a commercial version which apart from the plugboard and internal wirings, was the German Heer/Luftwaffe machine. The Japanese did not use it for their most secret communications, having developed a similar machine.
Army- and air force-related intelligence derived from signals intelligence (SIGINT) sources—mainly Enigma decrypts in Hut 6—was compiled in summaries at GC&CS (Bletchley Park) Hut 3 and distributed initially under the codeword "BONIFACE",implying that it was acquired from a well placed agent in Berlin. The volume of the intelligence reports going out to commanders in the field built up gradually. Naval Enigma decoded in Hut 8 was forwarded from Hut 4 to the Admiralty Operational Intelligence Centre (OIC), which were distributed initially under the codeword "HYDRO". The codeword "ULTRA" was adopted in June 1941. This codeword was reportedly suggested by Commander Geoffrey Colpoys, RN, who served in the RN OIC.
The distribution of Ultra information to Allied commanders and units in the field involved considerable risk of discovery by the Germans, and great care was taken to control both the information and knowledge of how it was obtained. Liaison officers were appointed for each field command to manage and control dissemination.
Dissemination of Ultra intelligence to field commanders was carried out by MI6, which operated Special Liaison Units (SLU) attached to major army and air force commands. The activity was organized and supervised on behalf of MI6 by Group Captain F. W. Winterbotham. Each SLU included intelligence, communications, and cryptographic elements. It was headed by a British Army or RAF officer, usually a major, known as "Special Liaison Officer". The main function of the liaison officer or his deputy was to pass Ultra intelligence bulletins to the commander of the command he was attached to, or to other indoctrinated staff officers. In order to safeguard Ultra, special precautions were taken. The standard procedure was for the liaison officer to present the intelligence summary to the recipient, stay with him while he studied it, then take it back and destroy it.
By the end of the war, there were about 40 SLUs serving commands around the world.Fixed SLUs existed at the Admiralty, the War Office, the Air Ministry, RAF Fighter Command, the US Strategic Air Forces in Europe (Wycombe Abbey) and other fixed headquarters in the UK. An SLU was operating at the War HQ in Valletta, Malta. These units had permanent teleprinter links to Bletchley Park.
Mobile SLUs were attached to field army and air force headquarters, and depended on radio communications to receive intelligence summaries. The first mobile SLUs appeared during the French campaign of 1940. A SLU supported the British Expeditionary Force (BEF) headed by General Lord Gort. The first liaison officers were Robert Gore-Browne and Humphrey Plowden.A second SLU of the 1940 period was attached to the RAF Advanced Air Striking Force at Meaux commanded by Air Vice-Marshal P H Lyon Playfair. This SLU was commanded by Squadron Leader F.W. "Tubby" Long.
In 1940, special arrangements were made within the British intelligence services for handling BONIFACE and later Ultra intelligence. The Security Service started "Special Research Unit B1(b)" under Herbert Hart. In the SIS this intelligence was handled by "Section V" based at St Albans.
The communications system was founded by Brigadier Sir Richard Gambier-Parry, who from 1938 to 1946 was head of MI6 Section VIII, based at Whaddon Hall in Buckinghamshire, UK.Ultra summaries from Bletchley Park were sent over landline to the Section VIII radio transmitter at Windy Ridge. From there they were transmitted to the destination SLUs.
The communications element of each SLU was called a "Special Communications Unit" or SCU. Radio transmitters were constructed at Whaddon Hall workshops, while receivers were the National HRO, made in the USA. The SCUs were highly mobile and the first such units used civilian Packard cars. The following SCUs are listed:SCU1 (Whaddon Hall), SCU2 (France before 1940, India), SCU3 (RSS Hanslope Park), SCU5, SCU6 (possibly Algiers and Italy), SCU7 (training unit in the UK), SCU8 (Europe after D-day), SCU9 (Europe after D-day), SCU11 (Palestine and India), SCU12 (India), SCU13 and SCU14.
The cryptographic element of each SLU was supplied by the RAF and was based on the TYPEX cryptographic machine and one-time pad systems.
RN Ultra messages from the OIC to ships at sea were necessarily transmitted over normal naval radio circuits and were protected by one-time pad encryption.
An intriguing question concerns the alleged use of Ultra information by the "Lucy" spy ring,headquartered in Switzerland and apparently operated by one man, Rudolf Roessler. This was an extremely well informed, responsive ring that was able to get information "directly from German General Staff Headquarters" – often on specific request. It has been alleged that "Lucy" was in major part a conduit for the British to feed Ultra intelligence to the Soviets in a way that made it appear to have come from highly placed espionage rather than from cryptanalysis of German radio traffic. The Soviets, however, through an agent at Bletchley, John Cairncross, knew that Britain had broken Enigma. The "Lucy" ring was initially treated with suspicion by the Soviets. The information it provided was accurate and timely, however, and Soviet agents in Switzerland (including their chief, Alexander Radó) eventually learned to take it seriously.
Most deciphered messages, often about relative trivia, were insufficient as intelligence reports for military strategists or field commanders. The organisation, interpretation and distribution of decrypted Enigma message traffic and other sources into usable intelligence was a subtle task.
At Bletchley Park, extensive indices were kept of the information in the messages decrypted.For each message the traffic analysis recorded the radio frequency, the date and time of intercept, and the preamble—which contained the network-identifying discriminant, the time of origin of the message, the callsign of the originating and receiving stations, and the indicator setting. This allowed cross referencing of a new message with a previous one. The indices included message preambles, every person, every ship, every unit, every weapon, every technical term and of repeated phrases such as forms of address and other German military jargon that might be usable as cribs .
The first decryption of a wartime Enigma message was achieved by the Poles at PC Bruno on 17 January 1940, albeit one that had been transmitted three months earlier. Little had been achieved by the start of the Allied campaign in Norway in April. At the start of the Battle of France on 10 May 1940, the Germans made a very significant change in the indicator procedures for Enigma messages. However, the Bletchley Park cryptanalysts had anticipated this, and were able—jointly with PC Bruno—to resume breaking messages from 22 May, although often with some delay. The intelligence that these messages yielded was of little operational use in the fast-moving situation of the German advance.
Decryption of Enigma traffic built up gradually during 1940, with the first two prototype bombes being delivered in March and August. The traffic was almost entirely limited to Luftwaffe messages. By the peak of the Battle of the Mediterranean in 1941, however, Bletchley Park was deciphering daily 2,000 Italian Hagelin messages. By the second half of 1941 30,000 Enigma messages a month were being deciphered, rising to 90,000 a month of Enigma and Fish decrypts combined later in the war.
Some of the contributions that Ultra intelligence made to the Allied successes are given below.
Rommel was appointed Inspector General of the West, and he inspected all the defences along the Normandy beaches and send a very detailed message that I think was 70,000 characters and we decrypted it as a small pamphlet. It was a report of the whole Western defences. How wide the V shaped trenches were to stop tanks, and how much barbed wire. Oh, it was everything and we decrypted it before D-Day.
The Allies were seriously concerned with the prospect of the Axis command finding out that they had broken into the Enigma traffic. The British were more disciplined about such measures than the Americans, and this difference was a source of friction between them.It was a little bit of a joke that in Delhi, the British Ultra unit was based in a large wooden hut in the grounds of Government House. Security consisted of a wooden table flat across the door with a bell on it and a sergeant sitting there. This hut was ignored by all. The American unit was in a large brick building, surrounded by barbed wire and armed patrols. People may not have known what was in there, but they surely knew it was something important and secret.
To disguise the source of the intelligence for the Allied attacks on Axis supply ships bound for North Africa, "spotter" submarines and aircraft were sent to search for Axis ships. These searchers or their radio transmissions were observed by the Axis forces, who concluded their ships were being found by conventional reconnaissance. They suspected that there were some 400 Allied submarines in the Mediterranean and a huge fleet of reconnaissance aircraft on Malta. In fact, there were only 25 submarines and at times as few as three aircraft.
This procedure also helped conceal the intelligence source from Allied personnel, who might give away the secret by careless talk, or under interrogation if captured. Along with the search mission that would find the Axis ships, two or three additional search missions would be sent out to other areas, so that crews would not begin to wonder why a single mission found the Axis ships every time.
Other deceptive means were used. On one occasion, a convoy of five ships sailed from Naples to North Africa with essential supplies at a critical moment in the North African fighting. There was no time to have the ships properly spotted beforehand. The decision to attack solely on Ultra intelligence went directly to Churchill. The ships were all sunk by an attack "out of the blue", arousing German suspicions of a security breach. To distract the Germans from the idea of a signals breach (such as Ultra), the Allies sent a radio message to a fictitious spy in Naples, congratulating him for this success. According to some sources the Germans decrypted this message and believed it.
In the Battle of the Atlantic, the precautions were taken to the extreme. In most cases where the Allies knew from intercepts the location of a U-boat in mid-Atlantic, the U-boat was not attacked immediately, until a "cover story" could be arranged. For example, a search plane might be "fortunate enough" to sight the U-boat, thus explaining the Allied attack.
Some Germans had suspicions that all was not right with Enigma. Admiral Karl Dönitz received reports of "impossible" encounters between U-boats and enemy vessels which made him suspect some compromise of his communications. In one instance, three U-boats met at a tiny island in the Caribbean Sea, and a British destroyer promptly showed up. The U-boats escaped and reported what had happened. Dönitz immediately asked for a review of Enigma's security. The analysis suggested that the signals problem, if there was one, was not due to the Enigma itself. Dönitz had the settings book changed anyway, blacking out Bletchley Park for a period. However, the evidence was never enough to truly convince him that Naval Enigma was being read by the Allies. The more so, since B-Dienst , his own codebreaking group, had partially broken Royal Navy traffic (including its convoy codes early in the war),and supplied enough information to support the idea that the Allies were unable to read Naval Enigma.
By 1945, most German Enigma traffic could be decrypted within a day or two, yet the Germans remained confident of its security.Had they known better, they could have changed systems, forcing Allied cryptanalysts to start again.
The exact influence of Ultra on the course of the war is debated; an oft-repeated assessment is that decryption of German ciphers advanced the end of the European war by two years. [ citation needed ] yet his assessment in Codebreakers is not specific:Hinsley is often cited as an authority for the two-year estimate,
Would the Soviets meanwhile have defeated Germany, or Germany the Soviets, or would there have been stalemate on the eastern fronts? What would have been decided about the atom bomb? Not even counter-factual historians can answer such questions. They are questions which do not arise, because the war went as it did. But those historians who are concerned only with the war as it was must ask why it went as it did. And they need venture only a reasonable distance beyond the facts to recognise the extent to which the explanation lies in the influence of Ultra.
Winterbotham's quoting of Eisenhower's "decisive" verdict is part of a letter sent by Eisenhower to Menzies after the conclusion of the European war and later found among his papers at the Eisenhower Presidential Library.It allows a contemporary, documentary view of a leader on Ultra's importance:
Dear General Menzies:
I had hoped to be able to pay a visit to Bletchley Park in order to thank you, Sir Edward Travis, and the members of the staff personally for the magnificent service which has been rendered to the Allied cause.
I am very well aware of the immense amount of work and effort which has been involved in the production of the material with which you supplied us. I fully realize also the numerous setbacks and difficulties with which you have had to contend and how you have always, by your supreme efforts, overcome them.
The intelligence which has emanated from you before and during this campaign has been priceless value to me. It has simplified my task as a commander enormously. It has saved thousands of British and American lives and, in no small way, contributed to the speed with which the enemy was routed and eventually forced to surrender.
I should be very grateful, therefore, if you would express to each and every one of those engaged in this work from me personally my heartfelt admiration and sincere thanks for their very decisive contribution to the Allied war effort.
Dwight D. Eisenhower
There is wide disagreement about the importance of codebreaking in winning the crucial Battle of the Atlantic. To cite just one example, the historian Max Hastings states that "In 1941 alone, ultra saved between 1.5 and two million tons of Allied ships from destruction." This would represent a 40 percent to 53 percent reduction, though it is not clear how this extrapolation was made.Another view is from a history based on the German naval archives written after the war for the British Admiralty by a former U-boat commander and son-in-law of his commander, Grand Admiral Karl Dönitz. His book reports that several times during the war they undertook detailed investigations to see whether their operations were being compromised by broken enigma code. These investigations were spurred because the Germans had broken the British naval code, and found the information useful. Their investigations were negative and the conclusion is that their defeat "... was due firstly to outstanding developments in enemy radar ... ." The great advance was centimetric radar, developed in a joint British-American venture, which became operational in the spring of 1943. Earlier radar was unable to distinguish U-boat conning towers from the surface of the sea, so they could not even locate U-boats attacking convoys on the surface on moonless nights; so the surfaced U-boats were almost invisible while having the additional advantage of being swifter than their prey. The new higher frequency radar could spot conning towers and periscopes could even be detected from airplanes. Some idea of the relative impact of codebreaking and radar improvement can be obtained from graphs showing the tonnage of merchantmen sunk and number of U-boats sunk in each month of the battle. Of course the graphs cannot be interpreted unambiguously, because we are unable to factor in many variables like improvements in code breaking and the numerous other advances in equipment to combat U-boats. Nonetheless the data seems to favor the German view—that radar was crucial.
While Ultra certainly affected the course of the Western Front during the war, two factors often argued against Ultra shortening the overall war by a measure of years are the relatively small role it played in the Eastern Front conflict between the Germans and the Soviet Union and the completely independent development of the U.S.-led Manhattan Project to create the atomic bomb. Author Jeffrey T. Richelson mentions Hinsley's estimate of at least two years, and concludes that "It might be more accurate to say that Ultra helped shorten the war by three months – the interval between the actual end of the war in Europe and the time the United States would have been able to drop an atomic bomb on Hamburg or Berlin – and might have shortened the war by as much as two years had the U.S. atomic bomb program been unsuccessful."Military historian Guy Hartcup analyzes aspects of the question but then simply says, "It is impossible to calculate in terms of months or years how much Ultra shortened the war."
While it is obvious why Britain and the U.S. went to considerable pains to keep Ultra a secret until the end of the war, it has been a matter of some conjecture why Ultra was kept officially secret for 29 years thereafter, until 1974. During that period the important contributions to the war effort of a great many people remained unknown, and they were unable to share in the glory of what is likely one of the chief reasons the Allies won the war – or, at least, as quickly as they did.
At least three versions exist as to why Ultra was kept secret so long. Each has plausibility, and all may be true. First, as David Kahn pointed out in his 1974 New York Times review of Winterbotham's The Ultra Secret, after the war, surplus Enigmas and Enigma-like machines were sold to Third World countries, which remained convinced of the security of the remarkable cipher machines. Their traffic was not as secure as they believed, however, which is one reason the British made the machines available. [ better source needed ]
By the 1970s newer computer-based ciphers were becoming popular as the world increasingly turned to computerised communications, and the usefulness of Enigma copies (and rotor machines generally) rapidly decreased. Switzerland developed its own version of Enigma, known as NEMA, and used it into the late 1970s, while the United States National Security Agency (NSA) retired the last of its rotor-based encryption systems, the KL-7 series, in the 1980s.
A second explanation relates to a misadventure of Churchill's between the World Wars, when he publicly disclosed information from decrypted Soviet communications. This had prompted the Soviets to change their ciphers, leading to a blackout.[ citation needed ]
The third explanation is given by Winterbotham, who recounts that two weeks after V-E Day, on 25 May 1945, Churchill requested former recipients of Ultra intelligence not to divulge the source or the information that they had received from it, in order that there be neither damage to the future operations of the Secret Service nor any cause for the Axis to blame Ultra for their defeat.
Since it was British and, later, American message-breaking which had been the most extensive, the importance of Enigma decrypts to the prosecution of the war remained unknown despite revelations by the Poles and the French of their early work on breaking the Enigma cipher. This work, which was carried out in the 1930s and continued into the early part of the war, was necessarily uninformed regarding further breakthroughs achieved by the Allies during the balance of the war. In 1967, Polish military historian Władysław Kozaczuk in his book Bitwa o tajemnice ("Battle for Secrets") first revealed Enigma had been broken by Polish cryptologists before World War II. Later the 1973 public disclosure of Enigma decryption in the book Enigma by French intelligence officer Gustave Bertrand generated pressure to discuss the rest of the Enigma–Ultra story.
In 1967 David Kahn in The Codebreakers described the 1944 capture of a Naval Enigma machine from U-505 and gave the first published hint about the scale, mechanisation and operational importance of the Anglo-American Enigma-breaking operation:
The Allies now read U-boat operational traffic. For they had, more than a year before the theft, succeeded in solving the difficult U-boat systems, and – in one of the finest cryptanalytic achievements of the war – managed to read the intercepts on a current basis. For this, the cryptanalysts needed the help of a mass of machinery that filled two buildings.
Ladislas Farago's 1971 best-seller The Game of the Foxes gave an early garbled version of the myth of the purloined Enigma. According to Farago, it was thanks to a "Polish-Swedish ring the British obtained a working model of the 'Enigma' machine, which the Germans used to encipher their top-secret messages.""It was to pick up one of these machines that Commander Denniston went clandestinely to a secluded Polish castle [!] on the eve of the war. Dilly Knox later solved its keying, exposing all Abwehr signals encoded by this system." "In 1941 [t]he brilliant cryptologist Dillwyn Knox, working at the Government Code & Cypher School at the Bletchley centre of British code-cracking, solved the keying of the Abwehr's Enigma machine."
The British ban was finally lifted in 1974, the year that a key participant on the distribution side of the Ultra project, F. W. Winterbotham, published The Ultra Secret. A succession of books by former participants and others followed. The official history of British intelligence in World War II was published in five volumes from 1979 to 1988, and included further details from official sources concerning the availability and employment of Ultra intelligence. It was chiefly edited by Harry Hinsley, with one volume by Michael Howard. There is also a one-volume collection of reminiscences by Ultra veterans, Codebreakers (1993), edited by Hinsley and Alan Stripp.
A 2012 London Science Museum exhibit, "Code Breaker: Alan Turing's Life and Legacy",marking the centenary of his birth, includes a short film of statements by half a dozen participants and historians of the World War II Bletchley Park Ultra operations. John Agar, a historian of science and technology, states that by war's end 8,995 people worked at Bletchley Park. Iain Standen, Chief Executive of the Bletchley Park Trust, says of the work done there: "It was crucial to the survival of Britain, and indeed of the West." The Departmental Historian at GCHQ (the Government Communications Headquarters), who identifies himself only as "Tony" but seems to speak authoritatively, says that Ultra was a "major force multiplier. It was the first time that quantities of real-time intelligence became available to the British military." He further states that it is only in 2012 that Alan Turing's last two papers on Enigma decryption have been released to Britain's National Archives; the seven decades' delay had been due to their "continuing sensitivity... It wouldn't have been safe to release [them earlier]."
Historians and holocaust researchers have tried to establish when the Allies recognized the full extent of Nazi-era extermination of Jews, and specifically, the extermination-camp system. In 1999, the U.S. Government passed the Nazi War Crimes Disclosure Act (P.L. 105-246), making it policy to declassify all Nazi war crime documents in their files; this was later amended to include the Japanese Imperial Government.As a result, more than 600 decrypts and translations of intercepted messages were disclosed; NSA historian Robert Hanyok would conclude that Allied communications intelligence, "by itself, could not have provided an early warning to Allied leaders regarding the nature and scope of the Holocaust."
Following Operation Barbarossa, decrypts in August 1941 alerted British authorities to the many massacres in occupied zones of the Soviet Union, including those of Jews, but specifics were not made public for security reasons.Revelations about the concentration camps were gleaned from other sources, and were publicly reported by the Polish government-in-exile, Jan Karski and the WJC offices in Switzerland a year or more later. A decrypted message referring to "Einsatz Reinhard" (the Höfle Telegram), from January 11, 1943, may have outlined the system and listed the number of Jews and others gassed at four death camps the previous year, but codebreakers did not understand the meaning of the message. In summer 1944, Arthur Schlesinger, an OSS analyst, interpreted the intelligence as an "incremental increase in persecution rather than... extermination."
There has been controversy about the influence of Allied Enigma decryption on the course of World War II. It has also been suggested that the question should be broadened to include Ultra's influence not only on the war itself, but also on the post-war period.
F. W. Winterbotham, the first author to outline the influence of Enigma decryption on the course of World War II, likewise made the earliest contribution to an appreciation of Ultra's postwar influence, which now continues into the 21st century—and not only in the postwar establishment of Britain's GCHQ (Government Communication Headquarters) and America's NSA. "Let no one be fooled," Winterbotham admonishes in chapter 3, "by the spate of television films and propaganda which has made the war seem like some great triumphant epic. It was, in fact, a very narrow shave, and the reader may like to ponder [...] whether [...] we might have won [without] Ultra."
Debate continues on whether, had postwar political and military leaders been aware of Ultra's role in Allied victory in World War II, these leaders might have been less optimistic about post-World War II military involvements.
Knightley suggests that Ultra may have contributed to the development of the Cold War.The Soviets received disguised Ultra information, but the existence of Ultra itself was not disclosed by the western Allies. The Soviets, who had clues to Ultra's existence, possibly through Kim Philby and Anthony Blunt, may thus have felt still more distrustful of their wartime partners.
The mystery surrounding the discovery of the sunk German submarine U-869 off the coast of New Jersey by divers Richie Kohler and John Chatterton was unraveled in part through the analysis of Ultra intercepts, which demonstrated that, although U-869 had been ordered by U-boat Command to change course and proceed to North Africa, near Rabat, the submarine had missed the messages changing her assignment and had continued to the eastern coast of the U.S., her original destination.
Bletchley Park is a nineteenth-century mansion and estate near Milton Keynes in Buckinghamshire, constructed during the years following 1883 for the English financier and politician Sir Herbert Samuel Leon in the Victorian Gothic, Tudor, and Dutch Baroque styles, on the site of older buildings of the same name. It has received latter-day fame as the central site for British codebreakers during World War II, although at the time of their operation this fact was a closely guarded secret. During the Second World War, the estate housed the British Government Code and Cypher School (GC&CS), which regularly penetrated the secret communications of the Axis Powers – most importantly the German Enigma and Lorenz ciphers; among its most notable early personnel the GC&CS team of codebreakers included Alan Turing, Gordon Welchman, Hugh Alexander and Stuart Milner-Barry.
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.
In cryptanalysis, gardening is the act of encouraging a target to use known plaintext in an encrypted message. It was a term used at the British Government Code and Cypher School at Bletchley Park, England, during World War II, for schemes to entice the Germans to include particular words, which the British called "cribs", in their encrypted messages. This term presumably came from RAF minelaying missions, or "gardening" sorties. "Gardening" was standard RAF slang for sowing mines in rivers, ports and oceans from low heights, possibly because each sea area around the European coasts was given a code-name of flowers or vegetables.
PC Bruno was a Polish/French signals intelligence station near Paris during World War II, from October 1939 until June 1940. Its function was decryption of cipher messages, most notably German messages enciphered on the Enigma machine. PC Bruno worked in close cooperation with Britain's decryption center at Bletchley Park.
The Biuro Szyfrów was the interwar Polish General Staff's Second Department's unit charged with SIGINT and both cryptography and cryptanalysis.
Cryptography was used extensively during World War II, with a plethora of code and cipher systems fielded by the nations involved. In addition, the theoretical and practical aspects of cryptanalysis, or codebreaking, was much advanced.
Alfred Dillwyn "Dilly" Knox, CMG was a British classics scholar and papyrologist at King's College, Cambridge and a codebreaker. As a member of the World War I Room 40 codebreaking unit, he helped decrypt the Zimmermann Telegram which brought the USA into World War I. He joined the GC&CS at the war's end.
Harold Hall "Doc" Keen (1894–1973) was a British engineer who produced the engineering design, and oversaw the construction of, the British bombe, a codebreaking machine used in World War II to read German messages sent using the Enigma machine. He was known as "Doc" Keen because of his habit of carrying tools and paperwork in a case resembling a doctor's bag. After the war he was awarded the O.B.E..
Peter Frank George Twinn was a British mathematician, Second World War codebreaker and entomologist. The first professional mathematician to be recruited to GC&CS. Head of ISK from 1943, the unit responsible for decrypting over 100,000 Abwehr communications.
Enigma is a 2001 espionage thriller film directed by Michael Apted from a screenplay by Tom Stoppard. The script was adapted from the novel Enigma by Robert Harris, about the Enigma codebreakers of Bletchley Park in the Second World War.
Sir Francis Harry Hinsley OBE was an English historian and cryptanalyst. He worked at Bletchley Park during the Second World War and wrote widely on the history of international relations and British Intelligence during the Second World War. He was known as Harry Hinsley.
Commander Alexander "Alastair" Guthrie Denniston was a British codebreaker in Room 40, first head of the Government Code and Cypher School (GC&CS) and field hockey player. Denniston was appointed operational head of GC&CS in 1919 and remained so until February 1942.
Frederick William Winterbotham was a British Royal Air Force officer who during World War II supervised the distribution of Ultra intelligence. His book The Ultra Secret was the first popular account of Ultra to be published in Britain.
John William Jamieson Herivel was a British science historian and former World War II codebreaker at Bletchley Park.
Marian Adam Rejewski was a Polish mathematician and cryptologist who reconstructed the Nazi German military Enigma cipher machine sight-unseen in 1932. The cryptologic achievements of Rejewski and colleagues Jerzy Różycki and Henryk Zygalski enabled the British to begin reading German Enigma-encrypted messages at the start of World War II, seven years after Rejewski's original reconstruction of the machine. The intelligence that was gained by the British from Enigma decrypts formed part of what was code-named Ultra and contributed—perhaps decisively—to the defeat of Germany.
Reservehandverfahren (RHV) was a German Naval World War II hand-cipher system used as a backup method when no working Enigma machine was available.
SIGINT is a contraction of SIGnals INTelligence. Before the development of radar and other electronics techniques, signals intelligence and communications intelligence (COMINT) were essentially synonymous. Sir Francis Walsingham ran a postal interception bureau with some cryptanalytic capability during the reign of Elizabeth I, but the technology was only slightly less advanced than men with shotguns, during World War I, who jammed pigeon post communications and intercepted the messages carried.
About 8,000 women worked in Bletchley Park, the central site for British cryptanalysts during World War II. Women constituted roughly 75% of the workforce there. While women were overwhelmingly under-represented in high-level work, such as cryptanalysis, they were employed in large numbers in important auxiliary work, such as: operating cryptographic machinery and communications machinery; translating of Axis documents; traffic analysis; clerical duties, and many more besides.
translated by Michaela Nierhaus