Ultra (cryptography)
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.[1] Ultra eventually became the standard designation among the western Allies for all such intelligence. The name arose because the intelligence 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.[2] Several other cryptonyms had been used for such intelligence.
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.[3][4] The U.S. used the codename Magic for its decrypts from Japanese sources, including the "Purple" cipher.[5]
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.[a]
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!"[b] 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.[7] 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,[8] "the war would have been something like two years longer, perhaps three years longer, possibly four years longer than it was."[9] However, Hinsley and others have emphasized the difficulties of counterfactual history in attempting such conclusions, and some historians, such as Keegan, have said the shortening might have been as little as the three months it took the United States to deploy the atomic bomb.[8][10][11]
The existence of Ultra was kept secret for many years after the war. Since the Ultra story was widely disseminated by Winterbotham in 1974,[12][13] 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 Field Marshal Erwin Rommel's Enigma communications, General 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."[14] Over time, Ultra has become embedded in the public consciousness and Bletchley Park has become a significant visitor attraction.[15] 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."[16]
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.[42] 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.[43] 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.[44]
The first decryption of a wartime Enigma message, albeit one that had been transmitted three months earlier, was achieved by the Poles at PC Bruno on 17 January 1940. 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.[27]
Some of the contributions that Ultra intelligence made to the Allied successes are given below.
Safeguarding of sources[edit]
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.[81][82] It has been noted with some irony 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.[27]
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.[83]
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),[84] and supplied enough information to support the idea that the Allies were unable to read Naval Enigma.[d]
By 1945, most German Enigma traffic could be decrypted within a day or two, yet the Germans remained confident of its security.[85]
Postwar suppression[edit]
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 now recognised as one of the chief reasons the Allies won the war – or, at least, as quickly as they did.
At least three explanations 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.[95]
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.
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.[96]
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.
Holocaust intelligence[edit]
Historians and Holocaust researchers have tried to establish when the Allies realized 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.[103] 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."[104]
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.[105] 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.[106] 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.[107] In summer 1944, Arthur Schlesinger, an OSS analyst, interpreted the intelligence as an "incremental increase in persecution rather than... extermination."[108]
Postwar consequences[edit]
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."[109]
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.[e]
Knightley suggests that Ultra may have contributed to the development of the Cold War.[110] 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, John Cairncross and Anthony Blunt,[110] 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 unravelled 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.
In 1953, the CIA's Project ARTICHOKE, a series of experiments on human subjects to develop drugs for use in interrogations, was renamed Project MKUltra. MK was the CIA's designation for its Technical Services Division and Ultra was in reference to the Ultra project.[111][112]