What was ultra

Because of increases in Allied escort strength and long-range aircraft patrols, one must hesitate in identifying Ultra as decisive by itself. I am sure that without the work of many unknown experts at Bletchley Park…the turning point of the Battle of the Atlantic could not have come as it did in May , but months, perhaps many months, later.

In that case the Allied invasion of Normandy could not have been possible in June , and there would have ensued a chain of developments very different from the ones which we have experienced. Belatedly, Ultra began affecting the air war on both the tactical and the strategic levels.

British decoding capabilities during the Battle of Britain did not provide major help to Fighter Command. On the other hand, throughout and , Ultra provided valuable insights into what the Germans and Italians were doing in the Mediterranean and supplied Allied naval and air commanders with detailed, specific information on the movement of Axis convoys from Italy to North Africa. By March , Anglo-American air forces operating in the Mediterranean had succeeded in shutting down Axis seaborne convoys to Tunisia.

Allied information was so good, in fact, that after a convoy had been hit, the German air corps located in Tunisia reported to its higher headquarters, ironically in a message that was intercepted and decoded:. The enemy activity today in the air and on the sea must in [the] view of Fliegerkorps Tunis, lead to the conclusion that the course envisaged for convoy D and C was betrayed to the enemy.

At hours a comparatively strong four-engine aircraft formation was north of Bizerte. Also a warship formation consisting of light cruisers and destroyers lay north of Bizerte, although no enemy warships had been sighted in the sea area for weeks. As was to be the case throughout the war, the Germans then drew the conclusion that traitors either in their own high command or elsewhere—in this case, in the Commando Supremo , the Italian high command—had betrayed the course of the convoys.

In the battles for control of the air over Sicily, Ultra proved equally beneficial. It enabled the Allies to take advantage of German fuel and ammunition shortages and to spot Axis dispositions on the airfields of Sicily and southern Italy.

In regard to U. Luftwaffe message-traffic intercepts indicated quite correctly how seriously Allied air attacks were affecting the German air wing, but these intercepts may have prompted Lt. Ira Eaker, the U. The second great attack on Schweinfurt in October , as well as the other great bomber raids of that month, proved disastrous for the Eighth Air Force crews who flew the missions. The Eighth lost sixty bombers in the Schweinfurt run.

Moreover, the U. While bomber attacks did inflict heavy damage on German aircraft factories, the industry was in no sense destroyed. Likewise, attacks on ball-bearing plants failed to have a decisive impact. Most important, the Eighth Air Force received long-range fighter support to make deep penetration raids possible. The initial emphasis in American strategic bombing attacks in late winter and early spring lay first on hitting the German aircraft industry and then on preparing the way for the invasion of the Continent.

In May, Lt. Carl Spaatz, commander in chief of U. In attacking that industry, Spaatz hit the Germans at their most vulnerable economic point. On May 12, , Bs attacked synthetic oil plants throughout Germany. On May 16, Bletchley Park forwarded to the Eighth an intercept canceling a general staff order that Luftflotten Air Fleets 1 and 6 surrender five heavy and four light or medium flak batteries each to Luftflotte 3, which was defending France.

Those flak batteries were to move instead to protect the hydrogenation plant at Troglitz, a crucial German synthetic fuel facility. In addition, four heavy flak batteries from Oschersleben, four from Wiener Neustadt, and two from Leipzig-Erla, where they were defending aircraft factories, were ordered to move to defend other synthetic fuel plants. This major reallocation of air defense resources was a clear indication of German worries about Allied attacks on the oil industry. On May 21, another Ultra decrypt noted: Consumption of mineral oil in every form [must] be substantially reduced…in view of effects of Allied action in Rumania and on German hydrogenation plants; extensive failures in mineral oil production and a considerable reduction in the June allocation of fuel, oil, etc.

On May 28 and 29, , the Eighth Air Force returned to launch another attack on the oil industry. These two attacks, combined with raids that the Italy-based Fifteenth Air Force had launched against Ploesti, reduced German fuel production by 50 percent.

On June 6, Bletchley Park passed along the following decrypted statement:. As a result of renewed interference with production of aircraft fuel by Allied actions, most essential requirements for training and carrying out production plans can scarcely be covered by quantities of aircraft fuel available. Baker four allocations only possible to air officers for bombers, fighters and ground attack, and director general of supply.

No other quota holders can be considered in June. To assure defense of Reich and to prevent gradual collapse of German air force in east, it has been necessary to break into OKW [German Armed Forces high command] reserves.

Allied bombers, however, promptly returned to undo their efforts. The punishing, sustained bombing attacks prevented the Germans from ever making a lasting recovery in production of synthetic fuel. Clearly, Ultra played a major role in keeping the focus of the bombing effort on those fuel plants.

Albert Speer, the German minister of armaments and munitions, had warned Hitler after the first attack in May The enemy has struck us at one of our weakest points. If they persist at it this time, we will no longer have any fuel production worth mentioning. Our one hope is that the other side has an air force general staff as scatterbrained as ours.

The intelligence officer who handled Ultra messages at the Eighth Air Force reported after the war that the intercepts indicated that shortages were general and not local. This fact, he testified, convinced all concerned that the air offensive had uncovered a weak spot in the German economy and led to [the] exploitation of this weakness to the fullest extent.

On the level of tactical intelligence, during the execution of Operation Overlord, Ultra also provided immensely useful information. Intercepts revealed a clear picture of German efforts and successes in attempting to repair damage that the Allied air campaign was causing to the railroad system of northern France.

A mid-May staff appreciation signed by Field Marshal Gerd von Rundstedt, commander in chief West, warned that the Allies were aiming at the systematic destruction of the railway system and that the attacks had already hampered supply and troop movements.

Ultra intelligence made clear to Allied tactical air commanders how effective the attacks on the bridge network throughout the invasion area were and the difficulties that German motorized and mechanized units were having in moving forward even at night. Ultra also gave Western intelligence a glimpse of the location and strength of German fighter units, as well as the effectiveness of attacks carried out by Allied tactical aircraft on German air bases. Furthermore, these intercepts indicated when the Germans had completed repairs on damaged fields or whether they had decided to abandon operations permanently at particular locations.

These attacks forced the Germans to abandon efforts to prepare bases close to the Channel and instead to select airfields far to the southeast, thereby disrupting German plans to reinforce Luftflotte 3 in response to the cross-Channel invasion.

When the Germans did begin a postinvasion buildup of Luftflotte 3, the destruction of forward operating bases forced it to select new and inadequately prepared sites for reinforcements arriving from the Reich. Ultra intercepts proceeded to pick up information on much of the move, which indicated bases and arrival times for the reinforcing aircraft.

Another substantial contribution of Ultra to Allied success was its use in conjunction with air-to-ground attacks. Obligingly, the Germans left their vehicles and radio equipment in the open. The strike effectively eliminated the headquarters and robbed the Germans of the only army organization they had in the West that was capable of handling large numbers of mobile divisions. Why were the British able to break some of the most important German codes with such great regularity and thereby achieve such an impact on the course of the war?

The Germans seem to have realized midway through the conflict that the Allies were receiving highly accurate intelligence about their intentions.

Nevertheless, like postwar historians, they looked everywhere but at their own encrypted transmissions. Enthralled with the technological expertise that had gone into the construction of Enigma, the Germans excluded the possibility that the British could decrypt their signals. After the sinking of the great battleship Bismarck in May and the rapid clearance of the supply ships sent out ahead of her from the high seas, the Kriegsmarine did order an inquiry.

Headed by a signals man obviously with a vested interest in the results , the board of inquiry determined that the British could not possibly have compromised the Enigma system. Rather, the panel chose to blame the disaster on the machinations of the fiendishly clever British secret services.

By , the success of British anti-submarine measures in the Atlantic once again aroused German suspicions that their ciphers had been compromised. In fact, the commander of U-boats suggested to German naval intelligence that the British Admiralty had broken the codes: B.

U [the commander of U-boats] was invariably informed [in reply] that the ciphers were absolutely secure. Decrypting, if possible at all, could only be achieved with such an expenditure of effort and after so long a period of time that the results would be valueless.

One British officer serving at Bletchley Park recalled that German cryptographic experts were asked to take a fresh look at the impregnability of the Enigma.

The Germans made a bad situation worse by failing to take even the most basic security measures to protect their ciphers. Among basic errors, the Germans started in midwar to reuse the discriminate and key sheets from previous months rather than generate new random selection tables.

If that were not enough, they particularly the Luftwaffe provided a constant source of cribs, which were the presumed decrypted meanings of sections of intercepted text. They enabled the British to determine Enigma settings for codes already broken. The cribs turned up in the numerous, lengthy, and stereotyped official headings normally on routine reports and orders, all sent at regular times throughout the day.

According to Gordon Welchman, who served at Bletchley Park for most of the war, We developed a very friendly feeling for a German officer who sat in the Qattara Depression in North Africa for quite a long time reporting every day with the utmost regularity that he had nothing to report. The German navy proved no less susceptible to such mistakes. The volume itself was of inestimable help to the cryptanalysts at Bletchley Park.

Although the Germans introduced a fourth rotor into the Enigma in March , thereby threatening once again to impose a blackout on their North Atlantic operations, the new machines employed only a small fraction of their technical possibilities.

Unfortunately for the U-boats, there was also considerable overlap between old and new Enigmas. As a result of these and other technical errors, the British were back into U-boat radio transmissions within ten days of the changeover. Furthermore, at about the same time, Bletchley Park decrypted a signal to U-boat headquarters indicating that the Germans were breaking the Allied merchant code.

One final incident should serve to underline the high price of German carelessness where security discipline was concerned. The "Lucy" ring was initially treated with suspicion by the Soviets. Most deciphered messages, often about relative trivia, were not alone sufficient as intelligence reports for military strategists or field commanders.

The organisation, interpretation and distribution of intelligence derived from messages from Enigma transmissions and other sources into intelligence was a subtle business. This was not recognised by the Americans before the attack on Pearl Harbor , but was learnt very quickly afterwards.

At Bletchley Park, extensive indexes were kept of the information in the messages decrypted. This allowed cross referencing of a new message with a previous one. The first decryption of a wartime Enigma message was achieved by the Poles at PC Bruno on 17 January , 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 , 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 , 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 , however, Bletchley Park was deciphering daily 2, Italian Hagelin messages. By the second half of 30, Enigma messages a month were being deciphered, rising to 90, a month of Enigma and Fish decrypts combined later in the war.

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, it is said, [62] [63] 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 flap across the door with a bell on it and a sergeant sat 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 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. 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. The analysis suggested that the signals problem, if there was one, was not due to the Enigma itself. 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 , [65] and supplied enough information to support the idea that the Allies were unable to read Naval Enigma.

By most German Enigma traffic could be decrypted within a day or two, yet the Germans remained confident of its security. While it is obvious why Britain and the U. 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 New York Times review of Winterbotham's The Ultra Secret , after World War II the British gathered up all the Enigma machines they could find and sold them to Third World countries, confident that they could continue reading the messages of the machines' new owners.

A second explanation relates to a misadventure of Churchill 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. Discussion by either the Poles or the French of Enigma breaks carried out early in the war would have been uninformed regarding breaks carried out during the balance of the war.

Nevertheless, the 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.

The British ban was finally lifted in , the year that a key participant on the distribution side of the Ultra project, F. Winterbotham, published The Ultra Secret. The official history of British intelligence in World War II was published in five volumes from to 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 , edited by Hinsley and Alan Stripp. After the war, surplus Enigmas and Enigma-like machines were sold to many countries around the world, which remained convinced of the security of the remarkable cipher machines.

Their traffic was not so secure as they believed, however, which is one reason the British and Americans made the machines available. Switzerland even developed its own version of Enigma, known as NEMA , and used it into the late s.

Some information about Enigma decryption did get out earlier, however. The same year, David Kahn in The Codebreakers described the capture of a Naval Enigma machine from U and noted, somewhat in passing, naval Enigma messages were already being read. Ladislas Farago 's 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. Dilly Knox later solved its keying, exposing all Abwehr signals encoded by this system.

By , 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. It was shortly after this, in , that a decision was taken to permit revelations about some Bletchley Park operations.

John Agar, a historian of science and technology, states that by war's end 8, people worked at Bletchley Park. It was the first time that quantities of real-time intelligence became available to the British military. It wouldn't have been safe to release [them earlier]. Historians have long attempted to establish when in the war the Allies recognized the full extent of German plans to eliminate the Jews, specifically, the extermination-camp system.

Nazi War Crimes Disclosures Act of made it official policy to declassify all Nazi war criminal records held by the U. Government and led to release of over decrypts and translations of intercepted messages. Robert Hanyok concludes that Allied communications intelligence, "by itself, could not have provided an early warning to Allied leaders regarding the nature and scope of the holocaust.

In retrospect, a decrypted message referring to " Einsatz Reinhard ", from January 11, , listing the number of Jews and others gassed at four death camps the previous year, clearly outlined the system, but codebreakers did not understand what the message was.

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.