Intelligence was the British success story of the Second World War. The Russian army broke the power of the Wehrmacht, and American industry provided the material superiority that allowed Britain to survive and triumph. The British war record was a mixed one, but in intelligence its victory over the Germans was indisputable. Stories about espionage and counterespionage, clandestine operations and prisoner-of-war escapes flooded the market after the war. The Wooden Horse, The White Rabbit, and M.R.D. Foot’s semiofficial SOE in France were all best sellers. But in 1974, the publication of The Ultra Secret by a former air intelligence officer, F.W. Winterbotham, opened a new chapter in the history of the European war. 1 Winterbotham, defying a strictly enforced government ban, revealed that through intercepting and decoding radio signals, the British had been able to read the strategic and tactical information being relayed at every level of the three German armed forces and many domestic messages as well. The Germans knew nothing of this. They thought the codes and ciphers for their “Enigma” machine were impregnable. The story of the British triumph became the best-kept secret of World War II.

Winterbotham’s account provoked heated comment. Claims and counterclaims about distortions in The Ultra Secret appeared in the letter columns of The Times. More revelations followed about Enigma keys and navigational beams, ciphers and codes. This was not the world inhabited by Smiley’s friends. The government did not prosecute. Instead, the Cabinet Office agreed to commission and then publish an official history of wartime intelligence, the first and, thus far, the only government to do so. They turned to F.H. Hinsley, a diplomatic historian and professor of international relations at Cambridge University and currently its vice-chancellor.

Hinsley was doubly qualified for the job: as a young St. John’s undergraduate he had been recruited for the naval section at Bletchley Park, a country house about fifty miles from London which became the wartime center of Britain’s cryptographic work. Hinsley and his colleagues were given free access to all intelligence archives, even those that could not be cited and might never come into the public domain. The authors made their way through the archives and the bureaucratic jungles at home and abroad. Their first volume appeared in 1979, the next two years later, and there is a third still to come. No one concerned with the Second World War can ignore these books, for they show the European struggle in a new light.

Intercepting and deciphering radio signals was an old intelligence art. The British had created small cryptographic departments (the Admiralty’s Room 40) during the First World War but had failed to actively pursue these efforts in the interwar period. The Germans, on the other hand, had marketed and named a Dutch-invented ciphering machine in the early 1920s. The Enigma machine was bought first by the German navy and then by the other German armed forces and security services. Now found only in intelligence museums, Enigma was an electrically powered mechanical box, resembling a typewriter, in which sets of drums or wheels marked with numbers and letters could be so manipulated as to re-encode an original cipher.

Machine encipherment set decoding problems of an entirely different kind from the ones traditionally handled by intelligence bureaus. Fortunately for the Allies, the Polish secret service had secured an adapted version of the Enigma machine and a small group of Polish mathematicians had unraveled its workings and devised ways to read its daily settings. Between 1933 and 1938, they secretly read a large amount of German Enigma traffic. Then a series of German advances defeated the Polish cryptographers, and after mid-December 1938 all efforts at decoding failed. Realizing that war was imminent, the Poles met with French and British representatives and presented each with an Enigma built in Poland and technical drawings of a machine (“Bombe”) devised for finding Enigma keys through the rapid and automatic testing of many thousands of possible combinations. A few Polish code breakers joined a French team working in Paris. Fleeing in 1942, they were captured by the Gestapo but did not reveal their secret. Aided by these early Polish and French efforts, the British started on their own crash program just before the war broke out.

Only in 1939, during the Munich crisis, was the small interwar Government Code and Cypher School moved to Bletchley Park. A hastily assembled team of some twenty “men of the professor type,” as they were called, mostly in their twenties or early thirties, were brought from Cambridge and Oxford to work on the Enigma problem. The main recruiters were two historians from King’s College, Cambridge, Frank Adcock and Frank Birch, both of whom had served as naval cryptographers during the First World War.2 The first group of recruits included linguists, historians, and classicists, but also, because of the new problems posed by Enigma, two or three mathematicians, among them Alan Turing, reputed the most brilliant of the Bletchley Park code breakers. The dons were followed by their students. King’s College alone contributed twelve cryptologists, more than any other single institution. These young academics, about sixty at the start of the war, augmented with recruits from other rapidly expanded intelligence departments, were to carry off the most important intelligence coup of the war. Their first success came in May 1940 with the cracking of the German air force Enigma key.


Intelligence gathered from the breaking of the “most highly secret” Enigma traffic from Germany was known as Ultra. This was handled by the small elite group of cryptographers and intelligence men and circulated only to a very restricted circle of users including Winston Churchill. In addition, and involving far more people at Bletchley Park, the “Y” service dealt primarily with wireless traffic in low- and medium-grade codes and ciphers which, because of their bulk and frequency, yielded a wide variety of tactical information bearing on current military operations. The “Y” service distributed this lower-grade intelligence to the military commands. Thanks to these sources, British intelligence could often literally read the German mind. It could do so reliably, at high speed, and without involving vulnerable agents. “Sigint”—all forms of intelligence from wireless signals—and especially Ultra were indestructible weapons.

The degree of British success in decoding varied considerably. Each German service had a variety of keys. By the end of the war, some twenty naval and two hundred non-naval keys had been identified. The easiest to read were the German air force keys; the naval keys were more difficult and the army’s the most recalcitrant of all. The Gestapo Enigma key was never broken; the underlying reason, I gather, was the scarcity of messages to be worked on. However, in the valuable and fascinating appendixes to Volume II, Hinsley notes that the British were reading the Enigma traffic of the SS and the German police. From the spring of 1942 until February 1943, they deciphered lists of prisoners at Dachau, Buchenwald, and Auschwitz; yet the “terrible secret” of Auschwitz was not publicly known until 1944. These lists recorded the number of inmates, new arrivals, and “departures by any means,” i.e., deaths. So far we have had no public account of what happened to this information, who knew about it, and why it took so long for the news to spread.

The interception, decoding, analysis, interpretation, and distribution of signal intelligence involved a vast administrative effort. In a series of dense but important chapters, Professor Hinsley discusses the organization of the intelligence community and the tangled story behind the development of Bletchley Park. The intelligence services before World War II were multiple, small, and competing. Among others, there were the intelligence divisions of the Admiralty, the War Office, and the Air Ministry. The Special or Secret Intelligence Service (SIS or MI6), which was responsible for espionage, and the Government Code and Cypher School, were both under the control of the Foreign Office. MI5 was responsible for counter-espionage. As in the United States, all had been starved of men and funds during the interwar period. The Foreign Office took little interest in the SIS, which attracted few men, and those were considered of doubtful quality. In fact, the SIS generally avoided university types lest they be tarred with Bolshevism, leaving that fertile field to their Soviet rivals. Anthony Blunt, Guy Burgess, Donald Maclean, and Leo Long were recruited from Cambridge as potential Soviet spies during the 1930s.

If Bletchley Park were to work effectively, the three service departments and the Foreign Office had to be convinced that cryptography and intelligence should be undertaken on an interservice basis. All the activities at Bletchley Park were placed under the control of “C,” Col. Stewart Menzies, the not very intelligent but highly respected head of the SIS. There evolved by 1941 an effective Joint Intelligence Committee and a Joint Intelligence Staff.

Those familiar with the interdepartmental wars fought in Washington (where visiting British cryptographers acted as liaison men between the estranged War and Navy Departments) and in Berlin (where the five or six intelligence bureaus fought each other as bitterly as they did the enemy) will appreciate the achievement this feat of coordination represented. The most nightmarish problems sprang from rivalries among the military services. The army, in particular, felt its needs were being neglected in favor of the Admiralty and the RAF. The neutral tone adopted by the authors of this history scarcely disguises the ferocity of the debate over integrating the different agencies. In the British case, however, and this was their great administrative triumph, rivalries were sufficiently moderated to create an efficient intelligence apparatus that soon surpassed that of its enemies.


Growth created its own problems. Bletchley Park swelled from 200 people in 1939 to some 10,000 by the end of the war. There were rebellions against “C” that had to be quelled, clashes between SIS, MI5, and the newly created Special Operations Executive (SOE), which was set up to carry on subversive warfare and sabotage. The historian Hugh Trevor-Roper, a wartime recruit to SIS, was accused, “tried,” and acquitted for consorting with the enemy MI5. These agencies were all working in the same overseas areas and often competed for the same local agents. The battles between SIS and SOE, the bête noire of “C,” were particularly fierce. The SOE tended to use unlikely characters for agents—“from pimps to princesses,” M.R.D. Foot put it3—as well as highly irregular methods, and “C” was a regular army man. Difficulties arose not only between Bletchley Park and Whitehall but between officers and civilians, the prewar professionals and the wartime recruits. This was particularly true of SIS, which preserved a number of eccentric traditions that newcomers found faintly ridiculous and reminiscent of another age. “C” had a green light outside his room, used green ink, etc. As Enigma intelligence proved its worth and as the three armed services recruited more and more civilians into their intelligence branches, some of these problems resolved themselves. The naval tracking room at Bletchley Park, for instance, was staffed entirely by civilians.

There were also allies to be considered. With regard to this part of the intelligence story, Professor Hinsley has said far less than one might hope; clearly the American side of the story has been vetted in Washington. The US started out very much the junior partner in the Enigma enterprise. Early successes with the Japanese diplomatic codes were not followed by similar penetration of the Japanese military-naval communications or by successes against the Germans. Some Ultra and Sigint intelligence had already been passed to Washington before Pearl Harbor. Thereafter, the flow accelerated, but as the Americans developed their own intelligence sections, relations were, in the author’s words, “not so smooth.” The SIS trained the first recruits of General “Bill” Donovan to the group that later became the Office of Strategic Services; but difficulties mounted as the Americans asserted their independence and insisted on having their own networks of secret agents in occupied France, the Balkans, and the Middle East.

Hinsley barely touches on such matters, but notes the arrival of the Americans at Bletchley Park in June 1942. Telford Taylor, one of a number of lawyers, was among the first to join the Ultra huts. Most seem to have “melted in” with the British teams. There were greater problems with the US Army and Navy Departments, particularly the latter, which was anxious to develop its own ability to decipher Enigma in the Atlantic as well as in the Pacific, where Americans had intelligence to themselves. Finally a peaceful division of responsibilities was worked out; during 1943 the submarine tracking rooms on both sides of the Atlantic worked closely with each other.

Hinsley has even less to say about cooperation, or the lack of it, with the Soviet Union. Almost from the start, the intense suspiciousness of the Soviet defense establishment prevented the kind of exchanges that took place with the US. Except when they needed immediate help, e.g., with the Arctic supply convoys, the Russians withheld all information about themselves and shunned contact. British intelligence about the Russian front came not from Russia—the British ceased to read the Russian codes in 1941—but from the German Enigma traffic. The British were markedly reluctant to reveal Enigma intelligence in part because the decrypts indicated that the Germans were reading a number of Soviet codes and ciphers. It took pressure from Churchill to make the rather disgruntled “C” send Enigma intelligence to Moscow in a camouflaged form from July 1941 until the end of 1942.

After Stalingrad, attitudes on both sides hardened. Despite intermittent attempts at cooperation, particularly when, in June 1943, the Soviets captured one of the German air force codes and a naval Enigma machine, both sides lost interest in any further exchanges. How much information did the Soviets receive from their agents—whether in Bletchley Park (where Leo Long was serving in the section that monitored German troop movements) or from those with access to Enigma decrypts? Kim Philby did brilliantly in the SIS where he was one of the few “outsiders” fully accepted by the prewar veterans, indeed the only one to be decorated after the war, and he would have seen information derived from Enigma. It is hard to answer such a question. Since, according to Hinsley, no signs of such leaks appeared in the German decrypts it seems likely that either the Soviet agents passed material already sent to Russia or disguised its Enigma source.

What contribution did Sigint and particularly Ultra make to the winning of the war? How does the newly available information affect the accounts of Churchill, Eisenhower, and the host of generals and historians who wrote without saying a word about Ultra? Hinsley answers these questions through a detailed treatment of the main British and Allied campaigns in all but the Pacific theaters of war. The result is a study of several volumes which is almost microscopic in its approach. Yet it is one of the author’s great strengths that he never claims more for intelligence than his evidence suggests. If he errs, it is on the side of excessive caution.

With regard to questions of high strategy, Ultra was not a determining factor. The disagreements over opening a second front depended on the larger considerations of politics, supply, and military readiness. Nor did Ultra cast much light on Hitler’s plans or his discussions with the German High Command. The British learned nothing from Enigma about the preparations in late 1940 for the invasion of Russia. They had Ultra information about German activities in the Balkans but their fixed ideas about Hitler’s intentions caused them to misread it. They were forewarned of the Crete invasion but did not have the means to stop it. How, in his next volume, will Hinsley treat the Arnhem disaster, about which it has been charged that Ultra information was tragically ignored?

During the first two years of the war, described in the first volume, the Germans retained the edge, although the early breaking of the German air force key made a difference in the August 1940 Battle of Britain, when information about the organization of the Luftwaffe and its order of battle allowed the British to make better use of the few men and planes available. Thereafter, other secret weapons, such as R.V. Jones’s radio beam systems, were of equal, if not greater, significance in defeating the German air offensive. In the land and sea wars, the lack of men and equipment was critical and the intelligence efforts were still too limited and too disorganized to offset them.

The intelligence situation began to improve during 1941. In his second volume, Professor Hinsley expands the fascinating account of the Atlantic war found in Patrick Beesly’s Very Special Intelligence (1978). During the first months of 1941, and then again in early 1943, the German U-boats almost succeeded in cutting off Britain from US supplies, which could have meant British defeat. The margin in each case was a narrow one; German sinkings of merchant ships exceeded what the British and Americans could immediately replace. In the Atlantic, U-boats were using “wolf-pack” tactics with deadly success, and breaking the U-boat Enigma key undoubtedly saved the British. The Bletchley Park naval section could produce a virtually complete chart of U-boat dispositions and the convoys could be rerouted without revealing the sources of Admiralty information.

But the Germans, too, had their triumphs; their naval deciphering service, called B-Dienst, had repeated success in reading the Admiralty ciphers, including the daily estimate of U-boat dispositions and the convoy rerouting ciphers. The Admiralty at first refused to make use of Typex, the ciphering machine used by the British army and air force and never cracked by the Germans. It relied primarily on ciphers with long subtractor tables which the Germans were able to reconstruct and read. Though each side was breaking the other’s ciphers, each believed that its own was invulnerable—one of the great ironies of the war. The U-boat commanders were assured that Enigma could not be read; repeated failures were blamed on French spies or the wretched Italians. In fact, the Italian high-grade naval cipher was never broken and the Italians’ losses mounted only when they were forced to adopt German medium-grade ciphers. Only in June 1943, too late to influence the battle of the convoys, did the Admiralty begin to use a new and more secure reciphering system.

In early 1942, just when the B-Dienst was having its great successes in the Atlantic war, the U-boat command added a fourth wheel—called “Shark”—to the Enigma machine. This defeated the code breakers until the end of 1942; any further delay might well have been fatal, for early in 1943 swarms of U-boats entered the North Atlantic. Even with “Shark” deciphered, the contest was uncomfortably close. In March, the naval staff, though not the naval tracking room, feared disaster. The murderous sea battle ended only when Admiral Doenitz recalled his killer packs in May 1943. In his most finely poised and dramatic pages, Professor Hinsley describes the seesaw contest of these months, a contest that the British could not afford to lose. Even more than in the Battle of Britain, Ultra made a decisive difference to the outcome.

During the North African campaigns the constant and rapid reading of the Luftwaffe Enigma and the later and more irregular breaking of the German army ciphers were key factors in Rommel’s defeat. In the first African campaigns, however, sparse and poorly organized intelligence provided little advantage to the British Eighth Army, which was outmaneuvered by Rommel. The British did not anticipate Rommel’s first attack in March 1941; in twelve days the “Desert Fox” regained all that General Wavell had taken during the previous three months. Though forced to halt and then to fight off a British counteroffensive, Rommel was ready in the summer of 1941 to storm Tobruk and advance into Egypt.

General Auchinleck, who replaced Wavell in July 1941, was better served by the code breakers. Many accounts of the war show Churchill as angrily impatient with Auchinleck’s failure to take the offensive. The reason, as Hinsley now makes clear, was that Churchill read the Luftwaffe orders revealed by Enigma. Intelligence allowed British bombers to intercept the Axis supply lines bringing essential replacements of men, tanks, and oil. The new-found ability to read the enemy’s medium- and low-grade communications was crucial for the timing of the British offensive in November 1941. It did not prevent the escape of Rommel’s troops from Cyrenaica at the end of the year.

Professor Hinsley’s detailed account of the “desert war” will increase the already high military reputation of Rommel. Even the ability to break German army codes did not mean one could always read his subtle and mercurial mind. In February 1942 Rommel again achieved a tactical surprise, and even when forewarned of his attack on Gazala in May, the British lost the battle. Few could have imagined that the Germans, surrounded and short of supplies, would attack rather than retreat and turn defeat into victory. Nor could signal intelligence reflect the dogged fighting ability of Rommel’s troops or the qualitative superiority of the German tanks and antitank weapons that made it difficult to destroy the Panzer corps even when it was forced onto the defensive. Against such a wily and stubborn opponent, however, intelligence was a necessary asset. General Auchinleck himself believed that, but for Sigint, Rommel would have reached Cairo in 1942.

Hinsley also provides ample ammunition for those critical of General Montgomery’s histrionic manner and excessive caution during and after the battle of El Alamein. Using Auchinleck’s campaign plans, based on Ultra information, he could well assure his troops that he knew precisely what Rommel proposed to do. Whitehall was less than happy with this public hint that Britain had a secret weapon. His famous victory owed a double debt to Enigma: it allowed the British bombers to sink the fuel tankers without which Rommel’s remaining Tiger tanks were helpless, and provided a running commentary on the deteriorating German supplies and manpower. Few other commanders could have known more about the weaknesses of their enemy.

By contrast, the absence of Enigma intelligence contributed to failures in economic prediction. The British believed that Germany was on a full war footing in 1939 and anticipated an economic collapse in 1941 and 1942. Consequently, they could not understand the rise in the enemy’s industrial production after heavy Allied bombing of the Ruhr in 1942. Hinsley makes the surprising statement that the British had no agents in Germany (Nazi spies sent to Britain were quickly caught and recruited as double agents) and there was little other intelligence to correct earlier misconceptions. Bletchley Park was, moreover, far less useful to the planners when the air war moved to Germany. It could do little to counter the efficiency of German air defenses.

The history of the war thus appears in a new light from Hinsley’s account. Winston Churchill, sharply criticized in recent war books (e.g., Stephen Roskill’s Churchill and the Admirals),4 emerges from its pages as one of the few who understood the uses and importance of intelligence at a time of general skepticism. On this and many other matters Professor Hinsley has produced information that is staggering in its richness and depth of detail. But his objectivity is almost numbing: these are not easy volumes to digest, not least because he refuses to name most of the participants, though many are already known. People become official titles; quarrels, however notorious, are described impersonally. Hinsley only rarely permits himself to describe events dramatically. An unpublished review by a former SIS official allegedly began, “This is a book by a committee about committees for committees.” In fact it is a work of scholarship in which the notes are superb, the maps intelligible, the indexes ample, and the appendixes full of essential information.

Cryptography was not a unique British achievement; many other nations had their own code-breaking victories. In one sense, at least, British success depended on the unshakeable German faith in the invulnerability of Enigma. Nevertheless, the reasons why the British surpassed their enemy in this respect were deeply ingrained in the homogenous society of Bletchley Park and could have existed only in England. For Bletchley Park, and the Ultra team in particular, was recruited through the old boy’s (and old girl’s) network—mathematicians and champion chess players, linguists and historians, “clever young men” recommended by heads of colleges and schoolmasters, “general purpose men” suggested by fellow club members and board associates. There was no formal security clearance—the mobilization of British intelligence was a last-minute, hurried affair. MI5, the counterespionage service, was itself careless. Anthony Blunt was expelled from a military-intelligence training course in September 1939 because of his past communist contacts only to be accepted by MI5 a few months later. And MI5 was scarcely popular among the other intelligence branches. It placed too much faith in personal contacts. Everyone was known to someone.

Once part of the Ultra team, its members were left to get on with their own problems. The senior common room atmosphere that so irritated Malcolm Muggeridge, an SIS recruit, was a natural product of the recruitment process. The Bletchley Park huts were staffed largely by men from Cambridge and Oxford sharing a common set of unspoken assumptions that made collaboration and secrecy possible despite bureaucratic divisions and moments of intense strain. This was a tighter and more donnish elite than the one Trevor-Roper found at the wartime SIS head-quarters—“part-time stock-brokers and retired Indian policemen, the agreeable epicureans from the bars of White’s and Boodle’s, the jolly, conventional exnaval officers and the robust adventurers from the bucket shop.”5 But even at Bletchley Park a price was paid for the informal ways that produced such brilliant results. There were apparently no leaks to the Nazis, yet even before the recent exposure of Leo Long, it was rumored that there were Soviet moles.

The retrospective scandals that have shaken the British establishment since the Anthony Blunt case were the reverse side of a brilliant coin. The trust and intimacy that made possible the achievements recounted by Professor Hinsley also made it easier for betrayal to be concealed. The same in-group atmosphere also explains why the Ultra secret was kept not only during the war but for some thirty years thereafter. This is not to minimize the importance of the organizational achievement at Bletchley Park—the coordination of ministries, the merging of cryptography and intelligence and of civilians and officers. But the reasons why the British were so much more successful than their German counterparts had deeper roots than bureaucratic achievements.

Not all accounts of Britain’s covert operations in wartime have been made available to the public. The threat of new scandals has made the Thatcher government somewhat wary of reviving old tales. Fortunately, this new caution does not extend to the publication of these books. But then these are celebratory volumes. Men and women from the very elite that Hitler so despised, untrained in the arts of intelligence, brought off a coup that shortened the war by between two and three years and saved countless lives. It seems fitting that British intelligence be the first to be so authoritatively commemorated. Hinsley is producing a study that students of World War II will have to consult for many years to come.

This Issue

October 21, 1982