Air University Review, July-August 1984

ULTRA: Some Thoughts on its
Impact on the Second World War

Dr. Williamson Murray

ONLY now, nearly forty years after the end of the Second World War, has the essential role and contribution of intelligence to the winning of that conflict become clear. Central to the new evaluation of that importance has been the discovery of the fact that throughout the war the intelligence services of the Western powers (particularly the British) were able to intercept, break, and read a significant portion of the top secret message traffic of the German military.1 The dissemination of that cryptographic intelligence to Allied commanders under the code name Ultra played a substantial and critical role in fighting the Germans and achieving an Allied victory.

THE breaking of the German high-level codes began with the efforts of the Polish secret service in the interwar period. By creating a copy of the basic German enciphering machine, the Poles were able to read German signal traffic through the 1930s with varying degrees of success. However, shortly before the Munich Conference in September 1938, the Germans introduced additional rotors into their enciphering machine--the so-called enigma machine--and in approximately mid-September, darkness closed over the German message traffic.2 The Poles continued their work nevertheless, and after the British guarantee in March 1939 to Poland, they passed along to Great Britain what they had thus far achieved. (Earlier, there had also been considerable cooperation between the Poles and the French.) Building on what they had learned from their continental allies, the British finally managed to break into some of the German codes in April 1940, just before the great German offensive against France and the Low Countries.3

This first success would soon be followed by others that would give Allied intelligence and commanders valuable insights into German intentions and capabilities. Nevertheless, these crytographic successes covered only a small proportion of the specific codes that the Germans used. The German navy at the end of 1943, for example, used up to forty different ciphers, all requiring different settings on the enigma machines. Given the priorities in the Battle of the Atlantic, the transmissions from U-boat to shore and from the commander of submarines to his boats received the highest priorities from British code breakers at Bletchley Park (the location of the major Allied code-breaking effort in Europe). Even with the exceptional resources available at that location and at that time, it would take the experts several days and in some cases up to a week to find the solution for a particular day's settings to the enigma machine.4

The task of getting invaluable intelligence information out to the field where it could be of direct help to Allied commanders was, of course, immensely difficult, especially given the fear that should the Germans find out that their codes were being compromised on a daily basis, the entire source of Ultra would dry up. In 1940 during the Battle of Britain, this need for concealment was not a great difficulty; but as the war spread throughout Europe and the Mediterranean, it became an increasing problem. Basically, the British and their American allies evolved a carefully segregated intelligence system that kept the flow of Ultra information down to a limited number-of senior commanders. The entire Ultra dissemination process lay outside of normal intelligence channels. For example, the intelligence officers at Eighth Air Force would not even know of the existence of Ultra and would not know what the Ultra officer's duties were. He, in turn, would talk only to General Carl Spaatz, General James H. Doolittle, and the Ninth Air Force commander. The system worked, for the Germans never caught on to how extensively their ciphers were being compromised.

Unfortunately, there were drawbacks. Intelligence can be of use only if it is placed in the hands of those who understand its significance. Three specific incidents underline this point with great clarity. The first occurred in early September 1944 as Allied armies were pursuing the beaten Wehrmacht back to the frontiers of the Reich. On 5 September, Bletchley Park made the following information available to Allied commanders in Western Europe:

For rest and refit of panzer formations, Aeeresgruppe [army group] Baker ordered afternoon fourth (4 September)6 to remain in operation with battleworthy elements: two panzer, one arc six panzer, nine SS and one nought (ten] SS panzer divisions, elements not operating to be transferred by AOK five for rest and refit in area Venloo--Arnhem--Hertogenbosch.5

This intelligence (along with a second Ultra confirmation on 6 September)6 indicated that at the very time when British plans for Operation Market Garden were to move forward, some of the best panzer divisions in the German armed forces would be refitting in the town selected as the goal of the British 1st Airborne Division and the final objective on the Rhine for the operation. Putting this message together with intelligence that soon began coming out of Holland from the Dutch underground that SS panzer units were refitting in the neighborhood of Arnhem, Allied commanders should have recognized that Operation Market Garden had little prospect of success. Unfortunately, they did not put these pieces together, and those at the highest level in Field Marshal Sir Bernard L. Montgomery's headquarters with access to Ultra refused to draw the correct conclusions.

A second example comes from a period three months after Operation Market Garden: December 1944. One of the unfortunate results of the rush to print after the Ultra secret was out has been the appearance of a number of legends with little basis in fact.7 One of the most persistenl is the legend thatultra gave no advance warning to Allied commanders in December 1944 that the Germans were preparing to launch a major counterthrust through the Ardennes.8 It is true that Hitler's sixth sense that German security measures had been compromised led him to undertake a series of unprecedented measures to veil the Ardennes attack.9 Thus, there were no overt, operational indications as to what the Germans intended. However, a number of other indicators were uncovered by the decoding of enigma messages. These indicated that the Germans were moving supplies as well as large numbers of troops into the region behind the Ardennes.10 Since the Germans were desperately low of supplies and troops, such allocations of resources could only portend major operations in the Ardennes. The Germans had no reason to expect that the Allies were planning to launch a major offensive in this area--especially since the Allies were so obviously trying to kick in the door to the Reich at so many other points. Unfortunately, the mood in higher Allied headquarters and in intelligence circles was close to a feeling that the war was virtually over and the Germans could not possibly launch an offensive.

The third case in which Ultra information was available but remained unused was in one instance during the Battle of the Atlantic. The Allies moved their convoys through the North Atlantic very much on the basis of Ultra information, when available, so that these great formations of merchant shipping could avoid the patrol lines of German submarines established to pick up their movement and course. In this particular case, decoding of enigma transmissions had picked up a heavy concentration of German submarines to the north of the Azores. Thus, a major convoy of aviation gasoline tankers from the refineries at Trinidad to the Mediterranean was rerouted to the south of the Azores. Unfortunately, because his escorts needed refueling and the weather was better to the north of the islands, the convoy commander disregarded his instructions, sailed to the north of the Azores, and ran smack into the U-boats. Only two of the tankers reached port. What made the episode even more surprising was the fact that the convoy commander had just come from a term of duty in the Admiralty's convoy and routing section, where he surely must have had some awareness as to the Admiralty's reasons for rerouting convoys.11

If Ultra information was misused at times, it is clear that such instances were the exception rather than the rule. However, it is difficult to assess Ultra's full impact on the war. At times (particularly early in the war), no matter how much Ultra tipped the British off to German intentions, the overwhelming superiority of the Wehrmacht made any successful use of the information virtually impossible. For example, enigma decodes in the spring of 1941 forewarned the British about German intentions against the Balkan states, first against Greece and then, after the anti-German coup in Yugoslavia, against that country as well. Such intelligence was, of course, practically useless, due to the overwhelming power that the Reich was able to deploy in the region at that time.12 On the other hand, from the intercepts and decodes during the summers of 1941 and 1942, the British government (particularly Churchill) was able to obtain an accurate picture of Rommel's tank strength and to determine that the British army had considerable superiority in numbers against the Afrika Korps in the North African theaters.13 What quantitative returns could not indicate were such factors as the technological superiority of some German tanks and particularly the qualitative superiority of German doctrine and training. The intercepts do help in explaining why Churchill kept such considerable pressure on Eighth Army commanders to attack Rommel.

IN war, so many factors besides good intelligence impinge on the conduct of operations that it is difficult to single out any single battle or period in which Ultra was of decisive importance by itself.14 Yet there is one instance where one can say that the intelligence achieved through the breaking of the German codes by itself played a decisive role in mitigating enemy capabilities. By the first half of 1941, as more and more submarines were coming on line, the German U-boat force was beginning to have a shattering impact on the trade routes on which the survival of Great Britain depended. The curve of sinkings of British, Allied, and neutral shipping was climbing upward ominously.15

Number of ships sunk Tonnage sunk
November 1940 12 146,613
December 1940 37 212,590
January 1941 21 126,782
February 1941 39 196,783
March 1941 41 243,020
April 1941 43 249,375
May 1941 58 325,492

Through the spring of 1941, the British had had virtually no luck in solving the German navy's codes. In mid-May 1941, however, the British captured not only a German weather trawler with considerable material detailing the settings for the naval codes but also a German submarine, the U- 110, with its cipher machine and all accompanying material.16 With these two captures, the British held the settings for the next two months for the German navy's enigma machines. Thus, the British were able to break into the U-boat traffic by the end of May. Also, because German U-boats were controlled closely from shore and a massive amount of signaling went back and forth to coordinate the movement of the wolf packs, the British gained invaluable information, ranging from the number of U-boats available to tactical dispositions and patrol lines. Moreover, once they had a full two months' experience inside the German U-boat traffic, British cryptologists were able to continue breaking the submarine message traffic for the next five months.17 The impact that this intelligence had on the Battle of the Atlantic was almost immediate.18

Number of ships sunk

Tonnage sunk
June 1941 61 310,143
July 1941 22 94,209
August 1941 23 80,310
September 1941 53 202,820
October 1941 32 156,534
November 1941 13 62,196

The dramatic, decline in sinkings (compared with those that had occurred during the first five months of the year) has no explanation other than that Ultra information enabled the British to gain a decisive edge over their undersea opponent. There was no introduction of new technology, no significant increase in the number of escorts available, and no extension of air coverage. Ultra alone made the difference.

Unfortunately for the Anglo-American powers, within two months of U.S. entrance into the war, the Germans introduced an entirely new cipher, Triton, which closed off the flow of Ultra decrypts for the remainder of 1942. Thus, at the very time that the vulnerable eastern and southern coasts of the United States opened up to German submarine operations, Ultra information on German intentions and operations ceased. Direction-finding intelligence was available, of course, but it remained of limited assistance.

When the Germans turned their full attention back to the Atlantic in early 1943, enormous convoy battles occurred with increasing frequency. German Admiral Karl Dönitz had available to him in the North Atlantic nearly one hundred submarines. In opposition, the Allies possessed far greater numbers of escort vessels, including escort carriers whose aircraft made U-boat shadowing of convoys almost impossible. Moreover, long-range aircraft from Newfoundland, Iceland, and Northern Ireland were reaching farther and farther into the Atlantic.

At the beginning of 1943, the Allied naval commanders enjoyed one further great advantage. Bletchley Park had succeeded once again in breaking the German naval ciphers.19 That intelligence proved somewhat less useful than the Ultra intelligence in 1941 that had allowed the British to steer convoys around U-boat threats. The Allies were able to carry out similar evasive operations at times, but the large numbers of German submarines at sea at any given time made such maneuvers increasingly difficult and oftentimes impossible. Initially during the great three-month battle from March to May 1943, the Allies were badly battered. In May, however, the Allies smashed the U-boat threat so decisively that Dönitz was forced to end the battle. Ultra intelligence played a major role in the turnaround. However, because of additions to Allied escort strength and increases in long-range aircraft patrols, one must hesitate in identifying the Ultra contribution as decisive by itself. Yet, the leading German expert on the Battle of the Atlantic does note:

I am sure that without the work of many unknown experts at Bletchley Park . . . the turning point of the Battle of the Atlantic would not have come as it did in May 1943, but months, perhaps many months, later. In that case the Allied invasion of Normandy would not have been possible in June 1944, and there would have ensued a chain of developments very different from the one which we have experienced.20

Meanwhile, Ultra affected the air war on both the tactical and on the strategic levels. British decoding capabilities were not sufficient during the Battle of Britain to provide major help to Fighter Command to defeat the German air threat.21 Similarly, for the first three years of Bomber Command's war over the continent, Ultra could provide little useful intelligence. On the other hand, throughout 1942 and 1943, Ultra information provided valuable insights into what the Germans and Italians were doing in the Mediterranean and supplied Allied naval and air commanders with detailed, specific knowledge of the movement of Axis convoys from the Italian mainland to the North African shores. By March 1943, Anglo-American air forces operating in the Mediterranean had virtually shut down seaborne convoys to the Tunisian bridgehead. Allied information was so good, in fact, that the German air corps located in Tunisia reported to its higher headquarters (in a message ironically intercepted and decoded):

. . . the enemy activity today in the air and on the sea must in [the] view of Fliezerkorps Tunis, lead to the conclusion that the course envisaged for convoy D and C was betrayed to the enemy. At 0845 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.22

As was to be the case throughout the war, the Germans drew the conclusion that traitors either in their 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 with German fighters for control of the air over Sicily, Ultra proved equally beneficial to Allied air commanders. It enabled them to take advantage of German fuel and ammunition shortages and to spot Axis dispositions on the airfields of Sicily and southern Italy.23 However, in regard to U.S. strategic bombing, Ultra may well have exerted a counterproductive influence in 1943. Intercepts from the Luftwaffe's message traffic indicated quite correctly how seriously Allied attacks in the air were affecting German air units, but these intercepts may have persuaded General Ira Eaker, Commander, Eighth Air Force in 1943, and his subordinate commanders to go to the well once too often. The second great attack on Schweinfurt in October 1943, as well as the other great raids of that month, proved to be disastrous for the Eighth Air Force crews who flew the missions. (Sixty bombers were lost in the Schweinfurt run.)24

Moreover, U.S.A.A.F. theories about the vulnerability of the German economy to precision bombing proved somewhat unrealistic. While bomber attacks did inflict heavy damage on the German aircraft industry, the industry was in no sense destroyed. Likewise, the attacks on ball-bearing plants failed to have a decisive impact. True, damage to Schweinfurt caused the Germans some difficulties, but the batterings that Eighth's bombers took in the August and October attacks were such that despite intelligence information that the Germans would he back in business quickly, the Eighth could not repeat the mission again.25

In 1944, however, the nature of Eighth's capabilities and target selection changed. Most important, the Eighth Air Force received the long-range fighter support to make deep penetration raids possible.26 The initial emphasis in the strategic bombing attacks in late winter and early spring of 1944 was in hitting the German aircraft industry and then in preparing the way for the invasion of the European continent. In May 1944, however, General Carl Spaatz persuaded Eisenhower that he possessed sufficient bomber strength to support both the invasion and a major new offensive aimed at taking out Germany's oil industry. In attacking that industry, Spaatz, in fact, would hit the Germans at their most vulnerable economic point. Not only would attacks on the oil industry have an immediate impact on the mobility of the Wehrmacht's ground forces, but increasing fuel shortages would prevent the Germans from training a new generation of pilots to replace those lost in the terrible attrition battles of the spring.

On 12 May 1944, 935 B-17s and B-24s attacked synthetic oil plants throughout Germany. Almost immediately, Eighth's commanders received confirmation through Ultra that these attacks threatened Germany's strategic position severely. On 16 May, Bletchley Park forwarded a message to Eighth canceling a general staff order that Luftflotten 1 and 6 (Air Fleets 1 and 6) surrender five heavy and four light or medium flak batteries each to Luftflotte 3 (assigned the task of defending France). Those flak batteries were to move instead to protect the hydrogenation plant at Troglitz, a crucial facility in Germany's synthetic fuel industry. In addition, four heavy flak batteries from Oschersleben, four from Wiener Neustadt, and two from Leipzig-Erla (defending aircraft factories) were ordered to move to defend other synthetic fuel plants.27 This major reallocation of air defense resources were clear indications of German worries about Allied attacks on their oil industry. On 21 May, another Ultra decrypt (originating headquarters not identified) 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., were to be expected.28

On 28 and 29 May 1944, Eighth returned to the skies over Germany to attack the oil industry again. These two attacks, combined with the raids that Fifteenth Air Force (in Italy) had launched against Ploesti, reduced German fuel production by 50 percent.29 On 6 June, Bletchley Park passed along the following decrypt:

Following according to OKL [German Air Force High Command] on Fifth. As a result of renewed interferences 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. Extending, therefore, existing regulations ordered that all units to arrange operations so as to manage at least until the beginning of July with present stocks or small allocation which may be possible. Date of arrival and quantities of July quota still undecided. Only very small quantities available for adjustments, provided Allied situation remains unchanged. In no circumstances can greater allocations be made. Attention again drawn to existing orders for most extreme economy measures and strict supervision of consumption, especially for transport, personal and communications flights.30

Throughout the summer, Albert Speer's engineers and construction gangs scrambled to put Germany's oil plants back together. As fast as they succeeded, however, Allied bombers returned to undo their reconstruction efforts. Throughout the remainder of the year, Allied eyes, particularly of American bomber commanders, remained fixed on Germany's oil industry. The punishing, sustained bombing attacks prevented the Germans from ever making a lasting recovery in their production of synthetic fuel.

Clearly, Ultra played a major role in keeping the focus of the bombing effort on those fuel plants. Speer had warned Hitler after the first attack in May 1944:

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!31

Speer's hopes were not realized, largely because Ultra intelligence relayed to Allied air commanders both the size and successes of German reconstruction efforts, as well as the enormous damage and dislocations to Germany's military forces that the bombing of the plants was causing. The intelligence officer who handled Ultra messages at Eighth Air Force headquarters reported after the war that the intercepts and decrypts of enigma transmissions had indicated that shortages were general and not local. This fact, he indicated, 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."32

On the level of tactical intelligence during the preparation and execution of Overlord, Ultra also was able to provide 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.33 A mid-May staff appreciation by Field Marshal Gerd von Rundstedt (Commander in Chief, Panzer Group 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.34 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 picking their way past broken bridges at night.35

Ultra intercepts 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 air on German air bases.36 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.37 Armed with this information, the Allies pursued an intensive, well-orchestrated campaign that destroyed the German's base structure near the English Channel and invasion beaches. These attacks forced the Germans to abandon efforts to prepare bases close to the Channel and to select airfields far to the southeast, thereby disrupting German plans to reinforce Luftflotte 3 in response to the cross-channel invasion.38

When the Germans did begin a postinvasion buildup of Luftflotte 3, the destruction of forward operating bases forced them to select new and inadequately prepared sites for reinforcements arriving from the Reich. Ultra intercepts picked up information on a substantial portion of the move and indicated bases and arrival times for many of the reinforcing aircraft.39

Another substantial contribution of Ultra to Allied success was its use in conjunction with air-to-ground attacks. Ultra intercepts on 9 and 10 June gave Allied intelligence the exact location of Geyr von Schweppenburg's Panzer Group West headquarters. Obligingly, the Germans left their vehicles and radio equipment in the open.40 The attack not only destroyed most of Panzer Group West's communications equipment but also killed seventeen officers, including the chief of staff.41 The strike effectively removed Panzer Group West as an operating headquarters and robbed the Germans of the only army organization in the west capable of handling large numbers of mobile divisions.

IT is worth examining the reasons why the British were able to break some of the most important German codes with such great regularity and with such an important impact on the course of the war. The Germans seem to have realized midway through the war that the Allies were receiving highly accurate intelligence about their intentions and moves. Nevertheless, like postwar German historians,42 the German military looked everywhere but at their own signals. Enthralled with the technological expertise that had gone into the construction of the enigma machine, the Germans excluded the possibility that the British could decrypt their signals.

After the sinking of the Bismarck and the rapid clearance from the high seas of the supply ships that the Germans had sent out ahead of her, the German navy did order an inquiry. Headed by a signal 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 board chose to blame the disaster on the machinations of the fiendishly clever British Secret Services.43 By 1943, the success of British antisubmarine measures in the Battle of the Atlantic 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.d.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.44

One British officer serving at Bletchley Park records that German "cryptographic experts were asked to take a fresh look at the impregnability of the Enigma. I heard that the result of this 'fresh look' appeared in our decodes, and that it was an emphatic reassertion of impregnability."45

The Germans made a bad situation worse by failing to take even the most basic security measures to protect their ciphers. Indeed, a significant portion of Bletchley Park's success was due to silly, procedural mistakes that the Germans made in governing their message traffic. Among other basic errors, the Germans in midwar started to reuse the discriminate and key sheets from previous months rather than generate new random selection tables.46 If that carelessness were not enough, the Germans (particularly the Luftwaffe) provided a constant source of cribs to enable the British to determine the engima settings for codes that had been broken. These cribs turned up in numerous, lengthy, and stereotyped official headings, usually in routine reports and orders all sent at a regular time of day.47 Gordon Welchman, who served at Bletchley Park for most of the war, reports that "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."48

The German navy proved no less susceptible to critical mistakes. Dönitz's close control of the U-boat war in the Atlantic rested on an enormous volume of radio traffic. The volume itself was of inestimable help to the cryptanalysts at Bletchley Park.49 Although the Germans introduced a fourth rotor into the enigma machine in March 1943, 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 also, there was considerable overlapping between old and new machines. As a result of these and other technical errors, the British were back into the North Atlantic U-boat radio transmissions within ten days of the changeover.50 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.51

One final incident should serve to underline the costliness of German carelessness where security discipline was concerned. The great German battleship Bismarck had broken out into the central Atlantic in May 1941 on a raiding expedition. After sinking the battle cruiser Hood, the Bismarck managed to slip away from shadowing British cruisers. The pursuing British admiral decided at 1810 hours on 25 May that the German battle ship was making for Brest. Within an hour, the Admiralty had confirmation through air force signals. Luftwaffe authorities had used their wireless transmissions to inform their chief of staff (then visiting Athens during the Crete operation) that the Bismarck was heading for Brest.52

OBVIOUSLY, there are important lessons that we in the West can learn from these German errors. To begin with, Patrick Beesly, who worked closely with the naval Ultra throughout the war, notes that "while each nation accepted the fact that its own cryptanalysts could read at least some of their enemy's ciphers, they were curiously blind to the fact that they themselves were being subjected to exactly the same form of eavesdropping."53 Above all, the Germans seem to have been overly impressed with their presumed superiority in technology. Thus, not only did they make elemental mistakes in their communications discipline, but they arrogantly refused to believe that their enemies might have technological and intelligence capabilities comparable to their own.

In recent years, there has been considerable interest in German operational and tactical competence on the field of battle.54 There is an important subheading to that competence: while historians and military analysts tell us that the Germans were extraordinarily good in the operational and tactical spheres, we should also recognize that the Germans were sloppy and careless in the fields of intelligence, communications, and logistics, consistently (and ironically) holding their opponents in contempt in those fields. Thus, we would be wise to examine the German example closely in all aspects of World War II. We can learn from the Germans' high level of competence in the tactical and operational fields; equally, we have much to learn from their failures in other areas. Above all, the German defeat in World War II suggests that to underestimate the capabilities and intelligence of one's opponents can have only very dangerous and damaging consequences for one's own forces.

Ohio State University, Columbus


1. There are, of course, a host of major works that have appeared in recent years that have discussed the breaking and reading of the German enigma encoding and decoding system. The intelligence based on Allied decrypts of that message traffic was called Ultra. Some of the more useful and accurate books on the value of this intelligence contribution are: F. H. Hinsley et al., British Intelligence in the Second World War, Vols. I and II (London, 1979 and 1982); Gordon Welchman, The Hut Six Story: Breaking the Enigma Codes (New York, 1982); Patrick Beesly, Very Special Intelligence (Garden City, 1978); R.V. Jones, The Wizard War (New York, 1978); Ronald Lewin, Ultra Goes to War (New York, 1978); Ralph Bennett, Ultra in the West: The Normandy Campaign 1944-45 (New York, 1979); and for the best German viewpoint available in English, Jürgen Rohwer, "Ultra and the Battle of the Atlantic: The German View," in Changing Interpretations and New Sources in Naval History, edited by Robert William Love, Jr. (New York, 1980).

2. Lewin, p. 39; Welchman's The Hut Six Story is particularly useful on how the enigma machines worked.

3. Lewin, p. 60.

4. Rohwer, pp. 441-42.

5. Public Record Office (PRO), DEFE 3/127/XL 9188, 5.9.44., 1152Z.

6. Ibid., DEFE 3/128/XL 9245,6.9.44., 0103Z.

7. The most egregious of these legends was the story in Anthony Cave-Brown's Bodyguard of Lies (New York, 1976), pp. 32-44, that Churchill and the British government had known of the great German bombing attack on the city of Coventry on 11 November but deliberately refused to take any special measures for fear of compromising Ultra. There is, however, no basis in fact for such a story. Readers who wish to know what happened at Coventry should consult Jones, pp. 146-52, and N. E. Evans, "Air Intelligence and the Coventry Raid," Journal of the Royal United Services Institute (September 1976).

8. In particular, Lewin, pp. 357-58.

9. Including unprecedented security measures; see Chester Wilmot, The Struggle for Europe (New York, 1952).

10. See Bennett, pp. 191-204. Bennett's book is particularly important, since it ties Ultra directly into the conduct of military operations in the West.

11. Kenneth A. Knowles, "Ultra and the Battle of the Atlantic: The American View," in Changing Interpretations and New Sources in Naval History, edited by Robert William Love, Jr. (New York, 1980), p. 442.

12. In particular, Hinsley et al., British Intelligence in the Second World War, Vol. I, Chapter 11.

13. See Hinsley et al., British Intelligence in the Second World War, Vol. II, Chapter 21.

14. I attended a lecture given by a leading historian from the Federal Republic of Germany who argued that never by itself was Ultra of decisive importance.

15. Captain Steven Roskill, The War at Sea, Vol. I (London, 1954), p. 616.

16. Beesly, pp. 73-75.

17. Ibid., p. 99; and Rohwer, p. 421.

18. Roskill, p. 616. The explanation for why June's figures remained so high is that it took the British more than a month to integrate the Ultra breakthrough gained by the U-110 coup into their convoy strategy. The rise that occurred in September and October resulted from the fact that U-boats were attacking Gibraltar convoys well within the range of long-range German reconnaissance aircraft. This aerial surveillance made it much more difficult for the Admiralty to hide their convoys. See Beesly, pp. 100-01.

19. Hinsley et al., British Intelligence in the Second World War, Vol. II, pp. 556-57.

20. Rohwer, pp, 442-43.

21. There is some dispute here. The British official historians argue that Ultra provided little direct support (see Hinsley et al., British Intelligence in the Second World War, Vol. I, pp. 176-77), while Harold Deutsch argues the opposite in "Ultra and the Air War in Europe and Africa," Air Power and Warfare, Proceedings of the Eighth Military History Symposium, USAF Academy, edited by Colonel Alfred F. Hurley and Major Robert C. Ehrhart (Washington, 1979), pp. 165-66.

22. U.S. Army Air Force, Ultra: History of U.S. Strategic Air Forces in Europe vs. German Air Force (Frederick, Maryland, 1980), p. 26. This is a reprint of a study completed at the end of the European conflict by Ultra intelligence officers assigned to U.S. Army Air Forces in Europe.

23. Ibid.

24. For a discussion of the air battle of attrition in 1943, see Williamson Murray, Strategy for Defeat: The Luftwaffe 1933-1944 (Montgomery, Alabama, 1983), Chapters V and VI.

25. For the best study of the Schweinfurt raid, see Friedhelm Golücke, Schweinfurt unit der strategische Luftkrieg 1943 (Paderborn, 1980). For information on the vulnerability of the ballbearings industry, see United States Strategic Bombing Survey Report, "The German Anti-Friction Bearings Industry," January 1947.

26. For a discussion of the fortuitous development of the longrange fighter escort, see Bernard Boylan, "The Development of the Long-Range Escort Fighter," unpublished manuscript, USAF Historical Research Center, Maxwell AFB, Alabama.

27. PRO DEFE 3/156, KV 4021, 16.5.44., 0558Z.

28. PRO DEFE 3/159, KV 4762, 21.5.44., 2054Z.

29. Albert Speer, Inside the Third Reich (New York, 1970), p. 348.

30. PRO DEFE 3/166, KV 6673. 6.6.44., 2356Z.

31. Speer, pp. 346-47.

32. PRO 31/20/,16, "The Handling of Ultra Information at Headquarters Eighth Air Force," Ansel E. M. Talbert, Major, U.S. Army Air Force. For Ultra messages further confirming German fuel difficulties, see Ultra: History of U.S. Strategic Air Forces in Europe vs. German Air Force, pp. 217, 224-25, and 234.

33. Among many other messages, see PRO DEFE 3/47, KV 3015, 6.5.44., 1316Z; DEFE 3/153, KV 3300, 9.5.44., 2301Z and KV 3292, 9.5.44., 1659Z; DEFE 3/155, KV 3763. 14.5.44., 0412Z; DEFE 3/158, KV 4690, 21.5.44. 0534Z; DEFE 3/161, KV 5445, 27.5.44., 2131Z; DEFE 3.163, KV 5825, 31.5.44., 0039Z; DEFE 3/163, KV 5999, 1.6.44., 15162.

34. PRO DEFE 3/155, 14.5.44., 0412Z.

35. Among many others, see PRO DEFE 3/58, XL2299,16.7.44.; DEFE 3/171, KV 7998, 14.6.44., 0753Z; DEFE 3/179, KV 9976, 28.6.44., 2135Z.

36. Among many messages, see PRO DEFE 3/154, KV 3/154, KV 3524, 11.5.44., 2032Z; DEFE 3/153, KV 3417, 10.5.44., 2033Z; DEFE 3/153, KV 3327, 9.5.44., 0845Z; DEFE 3/160, KV 5141, 25.5.44., 1020Z; DEFE 3/159, KV 4944, 23.5.44., 2054Z; and DEFE 3/168, KV 7135, 9.6.44., 1648Z.

37. Among others, see PRO DEFE 3/155, KV 3863, 14.5.44., 2020Z; and DEFE 3/153, KV 3430, 10.5.44., 2129Z.

38. PRO DEFE 3/163, KV 5762, 3.5.44., 1440Z.

39. Among others, see PRO DE FE 3/166, KV 6675, KV 6699, KV 6694, KV 6749, and KV 6735; see also Ultra: History of U.S. Strategic Air Forces in Europe vs. German Air Force, p. 196.

40. Bennett, p. 68. The messages on the location of Panzer Group West are in PRO DEFE 3/168, KV 7171,9.6.44.,2040Z; and KV 7225, 10.6.44., 0439Z.

41. Major L. F. Ellis, Victory in the West, Vol. I, The Battle of Normandy  (London, 1962), p. 258.

42. Paul Carell, Scorched Earth: The Russian-German War, 1943-1944 (New York, 1971), pp. 93-116. In this unremarkable and thoroughly unreliable work, Carell suggests that Germany's troubles were entirely the result of vicious traitors in the Führer's headquarters. As an example of the unintended irony that so often appears in Carell's work, the following passage ranks high, "General Laux [in the Demyansk salient during winter 1942/1943] spoke to Sixteenth Army over the directional radio link and put his anxieties to the Commander in Chief. This useful and secure [my emphasis] wireless link had been set up by 1st Luftwaffe signals regiment in May 1942. It was an excellent link and, above all, saved the many casualties which used to be incurred . . . in repairing the long distance cables . . . . And the new link, moreover, was free from interference." (Ibid., pp. 299-300) The irony of course is that the laid cables were secure (from interception and decryption); the radio messages were not.

43. Beesly, p. 94.

44. Quoted in ibid., p. 169.

45. Welchman, p. 133.

46. Ibid., p. 130.

47. Ibid., p. 131.

48. Ibid., p. 132.

49. Knowles, p. 448.

50. Rohwer, p. 441.

51. Ibid.

52. Hinsley, British Intelligence in the Second World War, Vol. I, p. 345. See also Beesly, p. 88, who speculates that this signal was occasioned because a high-ranking Luftwaffe officer had a close relative aboard the Bismarck.

53. Beesly, p. 69.

54. In particular, see Timothy T. Lupfer, The Dynamics of Doctrine: The Changes in German Doctrine during the First World War  (Leavenworth, 1981).


Williamson Murray (B.A., M.A., Ph.D., Yale University) is an Associate Professor of History and Director of the Military History and Strategic Studies Program at Ohio State University. He served as a Research Associate for the Airpower Research Institute, Maxwell AFB, Alabama, and as a maintenance officer while serving in the Air Force from 1964 to 1969. Two of his recent books are Strategy for Defeat: The Luftwaffe 1933-1944  (Air University Press, 1983) and European Balance of Power, 1938-1939: The Path to Ruin  (Princeton University Press, 1984). Dr. Murray is a previous contributor to the Review.


The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.

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