The Secret Lives of Codebreakers

by Sinclair McKay

  In other words, the RAF had succeeded brilliantly; the Luftwaffe having been repelled, there was little chance, with the season of storms now upon the English Channel, that the Germans could launch an effective troop landing. Hitler, the Chiefs calculated, would have to shelve preparations for the winter. It was precisely this sort of information, provided by Bletchley, that gave the forces what was termed a “crystal ball.” “So efficient did Bletchley become in handling this material,” wrote Aileen Clayton, “that there were even cases where, during poor conditions for reception, the German recipient of a signal was obliged to ask the sender for the message to be repeated, whereas our listening stations had recorded it fully the first time. This placed British Intelligence in the position of knowing the contents of a signal before the intended recipient.”2

  By late September, Hitler was starting to turn his attentions east, toward his projected invasion of Russia. Although the Luftwaffe had lost a great many men and planes throughout the Battle of Britain, however, this did not stop their aerial bombing campaign.

  The Blitz started on the afternoon of September 7, 1940. Dread-filled Londoners gradually became aware of a distant muffled roar, like thunder, approaching from the east as 350 German bombers darkened the horizon. The RAF, expecting an assault on their bases, had missed the attackers. Within minutes, the German planes were flying over the vast docks and warehouses of east London. As they dropped their incendiary bombs, the warehouses, filled with imported sugar, molasses, and timber, went up in a series of blossoming yellow and blue infernos.

  The daylight raids were not to continue, for too many of the German planes were picked off on their way back to base. But nightly bombing soon began, and even though the darkness hampered much of the Luftwaffe’s accuracy, the result was still devastation, and a population forced to seek shelter and sleep far underground in Tube stations. It was, and remains, unimaginably relentless—in the following months, some 19,000 tons of bombs fell on London alone.

  But with the coming of that ferocious onslaught to London, the cryptographers at Bletchley made a further breakthrough. Crucially, the Germans sent information about their bombers’ navigation beams—the beams that were supposed to keep them on course—via radio. These radio signals were picked up by the Y Services. And on being passed on to Bletchley, a new color of Enigma decrypt—“Brown,” for this section of the Luftwaffe—was assigned to the specific cracking of such messages.

  The operatives of Hut 6 rapidly succeeded in doing so. Within days the Air Ministry was receiving vital information concerning potential raids and the numbers of bombers that might be involved. Thanks to Enigma, as Oliver Lawn explains, the Air Ministry also had the wherewithal to “bend” the German navigation beams, thereby causing the planes to drop their loads in the wrong places: “One of the things the Germans used the Enigma machine for, in the early stages of the war, was directing their bombing of British cities—beam bombing. That’s an aeroplane going along a beam and another beam being set to cross it. And that was the point at which they dropped their bombs, over the center of the city.

  “Now, there was a code which set the angles of the beams. And if you could break the code, clever engineers could bend one of the beams so that the crossing point was over green fields, and not over cities.”

  London, of course, was not alone in bearing the brunt of the nightly assaults; British industrial cities from Birmingham and Liverpool to Manchester and Glasgow lived in expectation of receiving hits. The information Bletchley supplied was never conclusive, but they were able to identify squadrons and call signs and thus report on numbers. However, Bletchley Park was not able in 1940 to accurately identify disguised place names in messages. For that, what would be needed was not a bombe, but a physical codebook, for aliases are simply impossible to guess at.

  Thus the war acquired a new and terrible urgency. The deployment of British troops in foreign lands was one thing; the targeting of ordinary citizens in large cities—in other words, total war—was another. Although much was made at the time of the claim that “Britain can take it!,” the true effect upon morale, especially among the East Enders whose houses and streets were being flattened on a nightly basis, was more difficult to gauge.

  British government psychologists were extremely concerned about the possible effects upon large urban populations of subjection to Blitzkrieg of the kind suffered in Spain and Norway. Mass panic was predicted, along with a breakdown of law and order, and the development of a sort of collective psychosis. In fact, those first Luftwaffe raids upon London had demonstrated something quite different; a tangible sense of defiance among all the smoldering bricks and the shattered houses. But London was a vast city. What would be the effect in a smaller, perhaps more tightly knit community?

  The RAF campaign against German cities stepped up. That autumn, British bombers aimed for Munich and for arms factories in Essen; they also bombed Hamburg. In response, German bombers started roving more widely across Britain. And in November 1940, one particular raid led to a conspiracy theory involving Bletchley Park that has persisted to this day.

  The story, according to “end of war” reports from Bletchley itself, seemed to go like this: thanks to a “Brown” message decrypt from Enigma on November 11, 1940, the Park was able to tell Air Intelligence that there was to be a very heavy raid. The codename given to this raid was “Moonlight Sonata”; the reason for the name was that it was apparently to take place at the height of the full moon. The German planes would be led by navigation beams. And there was a list of four potential targets, each of which had been given codenames. One of the codenames was “Korn.”

  Just earlier, a German prisoner of war had told his interrogators that a heavy raid was planned on Birmingham or Coventry. On November 12, a “Brown” Enigma decrypt seemed to give navigation beam bearings showing that three of the potential targets were the heavily industrialized Midlands cities of Birmingham, Wolverhampton, and Coventry. The date for the raid was most likely to be the fifteenth.

  And so with this information, gleaned from Bletchley, Air Intelligence reported to the Prime Minister on the morning of the fourteenth, telling him that the target was possibly London—given the sheer size of the raid planned—but could also either be Coventry or Birmingham. After all, no one could know what the code word “Korn” signified. Both Midlands cities were likely targets, as both had high concentrations of manufacturing plants directly involved with the war effort. In the case of Coventry, many of these factories were within the bounds of the city center. As targets on a brightly moonlit night, they could hardly be easier.

  By 3 p.m. that day, radio signals finally made it clear that Coventry was to be the target, and that the raid was to take place that night.

  This is where the conspiracy theory begins. Why, it goes, were the people of Coventry given no warning? Why was no attempt made to stop a raid that loosed thousands of incendiaries and tons of high explosives, creating a hellish blaze that destroyed almost everything within the radius of a quarter of a mile, even the city’s cathedral? In other words, why was the old city of Coventry sacrificed in this conflagration?

  The reason, say the conspiracy theorists, is this: that to have deflected the bombing by sabotaging the navigation beams—or allowing RAF fighters to defend the city from the air—Churchill would have been effectively telling the Germans that he had access to their most secret transmissions. The Prime Minister, this theory goes, was therefore faced on November 14, with a hideous dilemma. Could he step in with this foreknowledge and order that Coventry be given full protection from the onslaught—but by doing so alert the enemy to the fact that its messages had been read? Or instead, should he allow the city to be put to the sword so that the secret of Bletchley remained unguessed at?

  In fact, the entire premise is flawed, but it nonetheless emphasises a wider truth about the work of Bletchley. For as soon as Enigma was broken, it became utterly vital that the Germans should never suspect that this was the case. As
many veterans have pointed out, if German Intelligence suspected that its communications had been breached, they would instantly have been rendered much more complex and potentially impenetrable.

  There was the later occasion, for instance, of the sinking of the Bismarck in 1941. The truth of the matter was that the German warship had been tracked after Bletchley had succeeded in cracking certain codes. But for the Germans not to suspect this, a pantomime was necessary. And so, hours before the ship was sunk, the RAF arranged for four reconnaissance planes to conduct a survey of that area of the ocean. When one of the planes “spotted” the Bismarck, it was spotted in turn by the ship’s crew, who alerted High Command. Thus it looked as if the vessel had been located by chance. A number of Bletchley’s other intelligence tips also had to be made to look like the inspired sleuthing of spies and agents on the ground.

  But the theory proposing that Coventry was sacrificed omits certain essential details. First, Churchill had left London for the country that afternoon before getting the message. When he was told that there might be a vast raid on London, his car turned back to the city. It was only when he returned to Whitehall in the evening that it was confirmed that the target was to be Coventry.

  Moreover, the jammers of the navigation beams were apparently set to the wrong frequency, an error that was not corrected until the following month. It also happened to be the case that Coventry did have anti-aircraft defences. But in the face of such an onslaught, such defences would always be of only limited use. “Coventry could never have been evacuated in time,” recalled WAAF Y Service operative Aileen Clayton. “It would certainly have been a physical impossibility to get all the guns and searchlights needed for defence, as well as the fire engines and other equipment, moved from other places to the target zone…with the information that was available to us, there was no way in which the city and its people could have been saved from that suffering.”3

  And so the center of Coventry was consumed in flames, the molten lead of the gutters pouring and hissing into the streams, the cathedral transformed into russet-glowing ruins. Some 558 men, women, and children were killed, and thousands more were injured.

  It is a subject that occupies Bletchley veterans to this day. Oliver Lawn—who, it should be remembered, worked on decrypting messages concerning German bomber flight paths—still thinks there is some ambiguity about the issue: “You will find people going on both sides of that argument. Now that’s a typical case. But there are other cities where the codes were broken in time and the bombs were diverted. Coventry is still controversial.

  “The head of our section—Stuart Milner-Barry—felt that it was Churchill,” adds Mr. Lawn. “Milner-Barry felt it was not a delay in breaking the code.”

  Another who took this view was Captain Frederick Winterbotham, who was there on the afternoon when it became apparent that the city would be bombed, and wrote that there was still a chance that a decision to evacuate Coventry could be taken:

  There were, perhaps, four or five hours before the attack would arrive. It was a longish flight north and the enemy aircraft would not cross the coast before dark. I asked the personal secretary if he would be good enough to ring me back when the decision had been taken, because if Churchill decided to evacuate Coventry, the press, and indeed everybody, would know we had pre-knowledge of the raid and some countermeasure might be necessary to protect the source which would obviously become suspect.

  It also seemed to me, sitting in my office a little weary after the sleepless bomb-torn night before, that there would be absolute chaos if everyone tried to get out of the city in the few hours available and that if, for any reason, the raid was postponed by weather or for some other reason, we should have put the source of our information at risk to no purpose.

  I imagine the Prime Minister must have consulted a number of people before making up his mind. In any case, the RAF had ample time to put their countermeasures into action, such as jamming any of the aids to navigation that the Germans might be using. In the event, it was decided only to alert all the services, the fire, the ambulance, the police, the wardens, and to get everything ready to light the decoy fires. This is the sort of terrible decision that sometimes has to be made on the highest levels in war. It was unquestionably the right one.4

  Oliver Lawn still finds himself musing on the subject: “There were others who took other views. We will never know.” Perhaps so. But this was not the only instance in which Churchill and Bletchley Park were suspected of having connived to withhold information. Years after the Japanese launched their devastating surprise attack upon the US base of Pearl Harbor in Hawaii in December 1941, thus bringing the Americans into the war, it was suggested by some sources that Bletchley Park, through its work on the “Purple” Japanese codes, had decrypted vital messages concerning Japanese military intentions. The allegation was that having seen such intelligence, Churchill ordered it to be suppressed so that the Americans would gain no advance warning, thus ensuring that the attack would bring the United States into the conflict.

  In fact, British Intelligence was anticipating an attack upon Malaya—there was no forecast of any strike against any American base. And there is one further point in the defence of Bletchley and the Prime Minister. During bombing raids carried out on British cities in the early months of 1941, the business of meddling with Luftwaffe navigational beams was much more successful; one night in May, twenty-three German fighters were brought down on Humberside. And a ferocious attack on Derby—planned to be on the same scale as Coventry—was largely thwarted.

  Even so, in such situations it was often a matter of bluff and counter-bluff. According to a recent work by Rebecca Ratcliff, there were times when the cryptographers would receive irrefutable evidence of forthcoming bombing raids in certain locations.

  During the Blitz of 1941, they worried in particular about air-raid countermeasures. Ordering the Air Raid Precautions (ARP) for the correct target well before the Luftwaffe bombers appeared in the sky would reveal foreknowledge of the bombing raid and jeopardize the intelligence source. The Hut 3 analysts directed that all ARP orders be postponed until the Germans began their raid preparations and turned on their radio guidance beams.

  These beams led the Luftwaffe planes to their targets.… In addition, the analysts suggested that ARP measures be ordered not only for the target revealed by Ultra but “in [other towns] also, preferably situated along the line of the…beam.” Then, if the Germans heard about the ARP measures, they would assume the British had been warned by the beams, rather than by Enigma messages.5

  Finally, Bletchley veteran Roy Jenkins—later Lord Jenkins of Hillhead and biographer of Churchill—observed that the attack on Coventry, while “shattering its monuments and shops,” ironically “did less damage to its aircraft factories.” He also pointed out that a raid that took place over Birmingham barely a week later was far more lethal, resulting in 1,353 deaths.6

  The same hideous moral dilemma implied in the treatment of Bletchley’s information about the raid on Coventry was to apply throughout the war. By the spring of 1941, the Blitz was largely over, as Hitler turned his full attention east toward Russia. But there were still those in British Intelligence who believed that a Nazi invasion of British shores was imminent, and it suited German Intelligence to give such false indications to divert attention away from genuine plans.

  It has also been said that Churchill and the British government knew of the systematic extermination of the Jews, which by 1941 was gathering horrifying pace, with vast numbers of men, women, and children being sent in cattle trucks to Auschwitz, Dachau, Treblinka, and Sobibor. In August 1941, there were seventeen decrypts, over the period of eight days, of German police messages—they concerned the shootings of thousands of Jews.

  In a radio broadcast given on August 25, Churchill said: “Whole districts are being exterminated. Scores of thousands, literally scores of thousands, of executions in cold blood are being perpetrated by the German police troops upon
the Russian patriots who defend their native soil. Since the Mongol invasions in the sixteenth century, there has never been methodical, merciless butchery on such a scale, or approaching such a scale…we are in the presence of a crime without a name.”

  So why did Churchill not mention the Jews? The reason was that to have done so would have been to reveal to the Germans, once again, that their messages had been intercepted. It was all Churchill felt that he could do to let it be known—at last—that the Allies were aware of the multiplying atrocities, and would do everything in their power to stop them.

  A little later, Bletchley was able to break into the codes dealing with German railways—the same railway lines that led to the concentration camps. To a certain extent, they were able to glean from these messages the forced deportation of waves of thousands upon thousands of people, the lines leading inexorably to these places of death. As some have seen it, railway lines are easy targets for bombers—they glitter in the moonlight. Should the Allies not at least have tried to cripple this infrastructure, to try and bring the deportations to an end?

  The answer, it seems, was the same: nothing could be done that would betray the Bletchley secret. In any case, such efforts would have been little more than a temporary hindrance to the Nazis; a railway line can be easily repaired. It was more fruitful to aim for larger military and industrial targets. The only way that the horror could be halted—no matter how fine and detailed the intelligence—was by halting Hitler himself.

  All this demonstrates Bletchley Park’s fearful responsibilities. From 1942, the Abwehr section of Bletchley Park found itself decrypting tables which turned out to be SS returns on the numbers of people entering and dying in the camps; mass extermination reduced to chilly, efficient bureaucracy. To know exactly what the enemy is planning—to know just how many hundreds, thousands of lives will be extinguished, to know such things in advance from secret messages—now seems a burden too great to imagine.