The Bletchley Park Codebreakers

by Michael Smith

  By the spring of 1943, the Double Cross system had developed deception into a fine art. But one of the Twenty Club’s most famous achievements did not involve a double agent at all. The Allied forces were now mopping up in North Africa and preparing to invade southern Europe. The most obvious stepping stone was Sicily, just a short hop across the Mediterranean from Tunisia. The problem was to find a way of giving the Germans the impression that General Eisenhower and his British colleague General Alexander had other plans, forcing the Germans to reinforce other areas and weakening the defences in Sicily.

  Charles Cholmondeley, the RAF representative on the Twenty Committee, devised Operation Mincemeat, a plan centred around the known level of collaboration between the Spanish authorities and the Germans. The idea was to drop the body of a dead ‘British officer’ off the coast of Spain, close enough to ensure it would be washed up on the beach, with the intention of making it look as if it had come from a crashed aircraft. He would be carrying documents indicating that the main thrust of the Allied attack would be somewhere other than Sicily. The Spanish would be bound to pass these on to the Germans who would reinforce their garrisons in the suggested targets at the expense of the real one.

  Montagu took charge of the operation, acquiring a suitable body from a London hospital and giving it the identity of Major William Martin, Royal Marines, an official courier. Attached to Martin’s wrist by a chain was a briefcase containing a number of documents, including a letter from one senior British general to another, discussing planned assaults on Greece and an unspecified location in the western Mediterranean, for which Sicily was to be a cover. A further letter from Lord Mountbatten, the Chief of Combined Operations, referred jocularly to sardines, which was rightly thought enough of a hint to make the Germans believe the real attack was going to be on Sardinia. The members of the Twenty Committee were highly inventive in their choice of other documents to be planted on the body. Two ‘used’ West End theatre tickets for a few days before the intended launch of the body were in his pocket to show that he must have been travelling by air. A photograph of Martin’s ‘fiancée’, actually that of a female MI5 clerk, was placed in his wallet. For several weeks, Cholmondeley carried two love letters from the ‘fiancée’ around in his pocket to give them the proper crumpled look. There was even an irate letter from Martin’s bank manager.

  The body was floated ashore near the southern Spanish town of Huelva from a submarine. The Allies now had to find out if the Germans had swallowed the bait and the only sure way of knowing was from Sigint. Noel Currer-Briggs was an Intelligence Corps officer in 1 Special Intelligence Section, a mobile Sigint unit operating in Tunisia. ‘We were stationed at Bizerta on top of a hill just outside Tunis and I remember we were inspected one day by Alexander and Eisenhower,’ he said. ‘There we were working away at the German wireless traffic coming from the other side of the Mediterranean and we were saying: “Oh yes. They’ve moved that division from Sicily to Sardinia and they’ve moved the other one to the Balkans” and these two generals were jumping up and down like a couple of schoolboys at a football match. We hadn’t a clue why. We thought: “Silly old buffers”. It wasn’t until 1953 when Montagu’s book The Man Who Never Was came out that we realized we were telling them that the Germans had swallowed the deception hook, line and sinker.’

  The Germans had been totally taken in by Mincemeat. Even two months later, when the invasion of Sicily had been launched, German intelligence continued to insist that the original plan had been to attack Sardinia and Greece and that it had only been switched to Sicily at the last moment. The ability the Allies now had, through Ultra, to tell whether or not the enemy had been fooled by deception operations was crucial to the Double Cross system as it prepared its biggest challenge, misleading the Germans over the Allied plans for D-Day. According to Bennett, a military advisor in Hut 3, ‘No other source could have proved the efficacy of the deception planners’ rumour-mongering so conclusively, relieving the operational commanders’ minds as they prepared an amphibious undertaking on an unprecedented scale.’

  The running of the Double Cross operations was helped immensely in July 1943 when Section V moved from St Albans to Ryder St, just off St James’s St, and a stone’s throw from both MI5 headquarters and the offices of the London Controlling Section, which was co-ordinating all deception operations. Now, whenever problems arose, MI5 officers could simply walk across the road to discuss them with their opposite numbers in MI6. ‘One always gets the impression of a tremendous rivalry and that sort of thing,’ said Hugh Astor. ‘And I suppose at the top, there can be rivalry. But at the lower level, one just has to get on with the job and I always found everybody very helpful. Even at the top, one can exaggerate the degree of thigh grabbing. The time scale was so short you couldn’t really have a long battle with anybody. I don’t think there was really enough time for bad blood to be created.’

  Mutual understanding of each other’s problems and knowledge of how the German intelligence services operated was fostered by the Radio Security Intelligence Conference which met at the MI5 headquarters every alternate Thursday and was attended by the key players within MI5, MI6, the service intelligence departments, the Radio Intelligence Section and Bletchley Park. Even before Cowgill’s replacement, those attending the meetings discussed a wide range of subjects ‘off the record’. The relaxation of Cowgill’s strict regulations turned the conference into an invaluable forum for discussing every aspect of the German intelligence networks, whether controlled by the British or not, Astor said. ‘I knew all that I needed to know about those organizations and the style and characteristics of the agents I was running, the techniques that they used and of course assisted very much by Ultra. One usually got advance information about the arrival of agents through Ultra, so one knew what training they had been through.’

  By now the main thrust of the Twenty Club’s operations was in preparing for D-Day. Churchill was as fascinated with deception as he was with espionage. At the Tehran Conference in November 1943 when the final decision was made to launch the invasion of Europe in mid-1944, the British Prime Minister told Stalin that ‘in wartime, truth is so precious that she should always be attended by a bodyguard of lies’. From that point on, the overall deception plan for D-Day was known as Operation Bodyguard. Planning for the operation came under the control of the Supreme Headquarters Allied Expeditionary Force (SHAEF), based at Norfolk House, St James’s Square, close to all the main participants on the Twenty Committee. From then on, the double agent handlers had to think continuously about the various elements of the deception plan and how the agents could be used to convince the Germans they were true. The Double Cross system became like a game of chess, with the agents resembling pieces, each being carefully moved into a position where it could contribute to the opponent’s demise.

  By the beginning of 1944, the Twenty Committee was controlling fifteen double agents. But only seven of these had wireless sets. Four of them were to be the key players in the deception plan to cover the actual D-Day landings, which was to be called Fortitude South. Although the reports of the letter-writing agents would also be used to point the Germans away from the Allies’ real plans, it was only those with wireless sets who could send messages in ‘real time’.

  Fortitude South evolved rapidly during the early months of 1945 but the bare bones of the plan remained the same. The Germans were to be led to believe that the Normandy landings were a feint attack, aimed at drawing German forces away from the main thrust of the Allied invasion, which would be against the Pas de Calais. This would ensure that the bulk of the German forces would be held back from the Normandy beaches, allowing the Allies time to establish a strong foothold in northern France from which they could break out towards Paris and then on to the German border. A completely mythical formation was invented, the First United States Army Group (FUSAG), supposedly commanded by General George Patton, a hero of the invasion of Sicily and a man whom the Germans would believe must be
heavily involved in the invasion of Europe, as indeed he later would be. FUSAG was supposedly grouped in East Anglia and south-eastern England and it was vital that the agents’ reports were co-ordinated to show that this was the case, and to downplay the mass of troops waiting in the south and south-west to attack the German defences in Normandy.

  The most spectacularly useful of the wireless agents used in the Fortitude South deception plan was Garbo. Although he had now been moved to Britain, his network was so large and so vital to the overall deception picture that virtually everything had to be closely co-ordinated on a day-to-day basis. The most important of the other agents who, in the parlance of the Twenty Committee, ‘came up for D-Day’, was the triple agent Brutus. Roman Garby-Czerniawski, a Pole, had led the Interallié resistance network in France and, once it was uncovered, volunteered to work for the Abwehr in London in order to save the other members of his group from execution. But on arrival in Britain he immediately told the authorities of his mission and was turned against the Germans. Two others should be mentioned as important to Fortitude South: the Yugoslav Dusko Popov, codenamed Tricycle, and Natalie ‘Lily’ Sergueiev (codenamed Treasure), a French citizen born in Russia, whose family had fled in the wake of the Bolshevik revolution.

  All four of these agents helped in building up Fortitude South, the false picture of the intended target of D-Day. Tricycle and Brutus, who was supposedly a member of a Polish unit attached to FUSAG, provided an order of battle for the fictitious formation so detailed that the Germans were not just supplied with details of individual units, strengths and locations, but even with reproductions of the insignia painted on the side of their vehicles. Treasure’s role was to report from the West Country that there were very few troops there, further pushing the Germans towards the view that the main thrust of the attack would be against the Pas de Calais. But she came close to blowing the whole plan. Sent to Lisbon to collect a radio set from the Abwehr, she told a former acquaintance she had met in the street that she was now working for the British Secret Service. When she returned, she confessed to considering warning the Abwehr as retribution for the British refusal to allow her to bring her dog to the UK without going through quarantine. She was swiftly retired and replaced by an MI5 operator, who had to imitate her distinctive method of sending Morse and loquacious messages. For several months after D-Day, the Treasure character was kept active for no other reason than that her messages were so long-winded that Bletchley Park was able to follow them through the Abwehr communications network and use them as cribs. Denys Page, who had taken over from Oliver Strachey as head of the ISOS section in early 1942, told Masterman that the cribs supplied by Treasure and Brutus had ‘absolutely saved our bacon’ after the Germans introduced more secure systems during 1944.

  But by far the most important and complex role was played by Garbo. At one point he had a network of twenty-seven agents, some of whom still survived from his freelance period before the British recruited him. They included a Swiss businessman based in Bootle, who had reported ‘drunken orgies and slack morals in amusement centres’ in Liverpool, and an enthusiastic Venezuelan living in Glasgow who had noted the willingness of Clydeside dockers to ‘do anything for a litre of wine’. The Swiss businessman died of cancer in the autumn of 1942, but his widow continued working for Garbo, becoming virtually his personal assistant. The Venezuelan also grew in stature, becoming Garbo’s official deputy and developing his own ring of agents in Scotland, one of whom was an ardent communist who actually believed he was working for the Soviet Union. The Abwehr codenamed this group of agents the Benedict Network. Garbo’s mistress, a secretary working in the offices of the War Cabinet, provided useful opportunities for valuable pillow talk. She, like the network’s wireless operator, believed that her lover was a Spanish Republican. Garbo had also successfully set up a large network of agents in Wales, mostly Welsh Nationalists but led by an ex-seaman, ‘a thoroughly undesirable character’, who was working for purely mercenary reasons.

  It is worth pointing out that – in the words of the official historian – ‘the reader should bear in mind that none of these people actually existed’. Nevertheless, they all contributed to the German dependence on Garbo as their most reliable source for intelligence on the Allied plans and set the scene for his key role in Fortitude. The German belief in the existence of FUSAG was steadily built up by a number of means, apart from false reports from the double agents. Dummy invasion craft nicknamed ‘Big Bobs’ were left out in the open in east-coast ports and mobile wireless vehicles travelling around south-east England broadcast messages from a number of different locations to fool the German radio interception units.

  During the second half of May 1944, Garbo told his German controller in Madrid that he had accepted a job in the Ministry of Information, which would give him access to details of all propaganda designed to cover up the invasion plans. By reading these ‘in reverse’ he would be able to detect the real plans, he said. On 29 May, he sent a message saying that he had now studied all the propaganda directives. ‘What I was clearly able to get out of it and what I consider to be of maximum importance is the intention to hide the facts in order to trick us,’ he said. He was bringing his Venezuelan deputy down from Scotland to assist him in sending off the messages. This man could not speak German, would they mind if he sent his messages in English. The Germans readily agreed and the stage was set for Garbo’s greatest triumph.

  In the early hours of 6 June 1944, D-Day, Garbo made repeated attempts to warn his Abwehr controller that the Allied forces were on their way. This move was agreed by SHAEF on the basis that it would be too late for the Germans to do anything about it but would ensure that they still believed in Garbo as their best-informed secret agent after the invasion had begun. As predicted, it only served to increase their trust in Garbo and paved the way for the next stage of the deception. Shortly after midnight on 9 June, as the Allied advance faltered, and with the elite 1st SS Panzer division on its way, together with another armoured division, to reinforce the German defences in Normandy, Garbo sent his most important message. Three of his agents were reporting troops massed across East Anglia and Kent and large numbers of troop and tank transporters waiting in the eastern ports, he said.

  After personal consultation on 8th June in London with my agents Donny, Dick and Derrick, whose reports I sent today, I am of the opinion, in view of the strong troop concentrations in south-east and east England, that these operations are a diversionary manoeuvre designed to draw off enemy reserves in order to make an attack at another place. In view of the continued air attacks on the concentration area mentioned, which is a strategically favourable position for this, it may very probably take place in the Pas de Calais area.

  Garbo’s warning went straight to Hitler, who ordered the two divisions back to the Pas de Calais to defend against what he expected to be the main invasion thrust, and awarded Pujol the Iron Cross. Had the two divisions continued to Normandy, the Allies might well have been thrown back into the sea. On 11 June, Bletchley Park deciphered a message from Berlin to Garbo’s controller in Madrid, saying that Garbo’s reports ‘have been confirmed almost without exception and are to be described as especially valuable. The main line of investigation in future is to be the enemy group of forces in south-eastern and eastern England.’

  Even once the war was over, senior German officers still believed that the Allies had intended to make their main assault on the Pas de Calais area and only decided not to because the Germans had massed troops there. During the postwar interrogations of senior Wehrmacht officers, one asked: ‘All this Patton business wasn’t a trick, was it.’’ ‘What do you mean by that?’ asked his British interrogator. ‘What I mean is this,’ the German said. ‘Were all those divisions sent to south-east England simply to hold our forces in the Pas de Calais?’ ‘I certainly imagine,’ the British officer replied, ‘that if you had denuded the Pas de Calais, they would have been used to attack that place, but since you did not
do so, they were equally available to reinforce Montgomery.’ ‘Ah,’ the German said with evident relief. ‘That is what we always thought.’

  17

  HOW DILLY KNOX AND HIS GIRLS BROKE THE ABWEHR ENIGMA

  KEITH BATEY

  Introduction

  In early 1940, two members of the Radio Security Service (otherwise known as MI8c), Hugh Trevor-Roper (later Lord Dacre) and E. W. B. Gill, who were only amateur cryptanalysts, broke some Abwehr signals which had been encrypted using simple manual ciphers. GC&CS had initially said it had no interest in the traffic, which it thought was of no relevance to the war. However, the Trevor-Roper and Gill successes kindled the interest of GC&CS, and that of the intelligence services, in the Abwehr signals. Bletchley took the work on, and issued its first Abwehr decrypt in April 1940.

  The Abwehr also employed a wide variety of cipher machines: Kryha (a form of geared disc), teleprinter machines such as the Siemens and Halske T52 (Sturgeon), and the Lorenz SZ40/42 (Tunny), and different types of Enigma, including one known as the Zählwerke (‘counter’) machine (since it had a letter counter). GC&CS recognized that some of the Abwehr traffic was machine-enciphered. When the daily intercepts increased to a modest number, they were given to the legendary Dilly Knox to tackle. In this chapter, Keith Batey explains how Knox solved the counter machine in October 1941 with the help of Mavis Lever and Margaret Rock.

  The first Abwehr Enigma decrypt was issued on 25 December 1941 in a series that became known as ISK. By the end of the war, over 140,000 ISK decrypts had been circulated. Initially, they did not yield much useful intelligence, but that very soon changed when the volume of traffic increased. In May 1943, for example, they gave information on Chetnik and Partisan operations in Yugoslavia, shipping reports from Spain and Portugal, especially on Gibraltar, agents in various countries, and espionage arrangements generally, including sabotage at Gibraltar. But as Michael Smith has shown in Chapter 16, its most important role lay in revealing what the Abwehr really thought about reports from the double agents, such as Garbo, who were being used in the Double Cross operation.