The Storm of War: A New History of the Second World War

by Andrew Roberts

  For those who would prefer other explanations to divine intervention, the story of the cracking of the Enigma machine is also full of secular miracles. The design was patented by a Dutchman, H. A. Koch, in 1919, and by 1929 had been bought by the German Army and Navy (which used different versions of it). Looking like a normal typewriter but with three, four or five twenty-six-spoke rotor wheels attached, as well as lights and plugs that resembled a telephonist’s board, the machine had the ability to transform a typed message into a code so complicated that the Germans assumed it could never be broken. ‘To give an idea of how secure these machines are,’ General Franco’s intelligence officer Commander Antonio Sarmiento wrote in a 1936 report, when the Nationalists were buying ten Enigma machines from the Germans at the start of the Spanish Civil War, ‘suffice to say that the number of combinations is a remarkable 1,252,962,387,456.’4

  The technical side of the Enigma story is ferociously complex, and involves specialist terms such as the Banburismus procedure, Caesar reflector, Dolphin, Porpoise, Shark and Triton nets (that is, sub-codes), the Eins catalogue, Cillis, the Herivel Tip, codes-within-the-code, Gamma wheels, perforated sheets and plugboard connections, rodding, Bigram tables, bombes, cross-ruffing, straight-cribs and a related code entitled Geheimschreiber (secret writer).5 The cracking of Enigma and its related codes – such as the Japanese diplomatic cipher Purple which was transformed into decrypts codenamed Magic – was a genuine Allied operation, involving the secret services of Poland, France, Britain, Australia and the United States. It began as early as 8 November 1931, when a traitor working in the German Cipher Office called Hans Thilo Schmidt allowed the French Deuxième Bureau (secret service) to photograph the Enigma operating manuals, which he had momentarily spirited out of a safe in the War Ministry. The French told the British, who subsequently told the Poles about the machine, but none could crack the code without building a replica of the machine itself. This was achieved by the Polish cryptographer Marian Rejewski in December 1932, although the Poles did not initially inform the French and British that this had happened. From that point on, the Poles could read Wehrmacht and Kriegsmarine radio traffic, although when in 1937 the latter changed its Enigma indicating key (the setting on a vital cog) the naval side fell silent, and was to remain so for the next three crucial years. Changes in the machines instituted by the Germans in December 1938 (installing an extra two rotor wheels, bringing the total to five) and January 1939 (doubling the number of plugboard sockets) also plunged the Poles into darkness. In late July 1939 they finally told the French and British secret services that they had been reading the German traffic until late 1938.

  Ultra was not the sole means by which the Allies gathered intelligence, of course. Prisoners were captured and interrogated; simpler signals intelligence (sigint) codes used by front-line communications were eavesdropped upon and decoded by a British organization known as the Y Department; aerial photo-reconnaissance was interpreted at Medmenham on the Thames; resistance groups in Occupied Europe passed on information; SIS produced human intelligence (humint) from its own sources, although many were compromised early on in the war during the disastrous incident when in November 1939 two SIS officers, Captains Payne and Best, were kidnapped at Venlo on the Dutch–German border by Gestapo agents posing as Resistance figures; German generals in British captivity were eavesdropped upon when they discussed important subjects such as rocketry. Nonetheless, Ultra was by far the most important intelligence source and, because of its direct nature, the least corruptible in analysis. The Bletchley code-breakers were, as Churchill put it, ‘the geese who laid the golden eggs’ and who, just as importantly, ‘never cackled’. They were also almost all amateurs, recruited from civilian life, although their contribution was far to outweigh that of the career intelligence officers of the day.6

  After the invasion of Poland in September 1939, several senior Polish cryptographers escaped with their replica Enigma machine and were installed by the Deuxième Bureau in a château near Paris, where they began – with British and French help – to decode messages, although at the time it took them two months to do so, meaning that the information they divulged had usually been long superseded by events. On 12 February 1940, however, the German submarine U-33 was attacked off the west coast of Scotland and two of the extra rotor wheels used by the naval Enigma were captured. Five weeks later, a brilliant, eccentric, accident-prone, homosexual Cambridge mathematics don called Alan Turing installed something known as a bombe machine, an electro-mechanical device which made hundreds of computations every minute, at the Government Code and Cypher School at Bletchley Park in Buckinghamshire, 40 miles north-west of London. Other heroes of Bletchley were to include the mathematicians Stewart Milner-Barry and Alfred Dilwyn (‘Dilly’) Knox. In modern computing parlance, while the Poles provided the Enigma hardware, the assorted civilian geniuses stationed at Bletchley provided the software that produced Ultra.

  Far from being a school, Bletchley was a department of SIS, operating from a Victorian mansion that housed 150 workers in 1939, before expanding into huts in the grounds to fit 3,500 people by 1942 and no fewer than 10,000 by the end of the war. (Several of the huts can still be seen today, including the ones where the most important work was done, along with captured Enigma machines and the bombe predecessors of the computer.) Huts 6 and 3 deciphered, translated, annotated and passed on Wehrmacht and Luftwaffe signals, while Huts 4 and 8 (run by Turing and subsequently the chess champion Hugh Alexander) did much the same thing for the Kriegsmarine, sending reports to the Naval Intelligence Division of the Admiralty. Hut 4 also analysed sudden increases and decreases of signals traffic volume, which could suggest possible enemy intentions. On 4 April 1940, five weeks before Hitler unleashed Blitzkrieg on the West, same-day decoding of the German Army codes first became possible, but on 1 May the British at Bletchley and Poles in France were ‘blinded’ for three weeks when the Germans altered their indicating systems.7 Overall, however, Wehrmacht and Luftwaffe signals were decoded between three and six hours after they were sent, and naval signals during the battle of the Atlantic could be read as swiftly as one hour after transmission.8

  Before May 1940 the cracking of the codes depended upon chance factors such as the transmission of flaws and errors, as with one German unit reporting every morning the same phrase, Verlauf ruhig (situation unchanged), thus giving the Cambridge mathematics don in Hut 6, Gordon Welchman, who had improved Turing’s bombe machine in 1940, a vital clue about several letters.9 The major expansion of the Luftwaffe before the war meant that its signallers were generally less well trained and disciplined, and more sloppy, than their Army and Navy counterparts. The fact that there were only twenty-six letters in the alphabet, the key flaw in the machine that no letter could represent itself in the code, and the absence of number keys meaning that every number had to be spelt out, also encouraging replication, were the major aids to decryption. The vast number of permutations – just under 1,253 trillion – that the Enigma code depended upon could therefore be narrowed down considerably by Turing’s and Welchman’s bombes.

  It was not until the beginning of April 1941 that the German naval Enigma codes were broken – except for a very brief period in April 1940 – although there had been no shortage of plans to try to obtain German codebooks to help the process along, with the scheme of the intelligence officer and future Bond author Ian Fleming to crash a captured aircraft into the English Channel, and then ambush the rescue boat, being the most hare-brained.10 It turned out to be the capture off Norway of the German trawler Krebs that yielded up the vital settings list that Bletchley needed to operate Turing’s Banburismus procedure for decryption. Although all German skippers were under strict instructions to destroy or throw overboard all codebooks at all costs, with the capture by HMS Bulldog and HMS Broadway of soaking codebooks from Julius Lemp’s U-110 on 9 May 1941 by Sub-Lieutenant David Balme – they were dried over a stove on a British destroyer by Lieutenant Allon Bacon from the Naval In
telligence Division – Bletchley was able to discover future settings, the so-called Offizier procedure. This meant it could pick up announcements of future settings changes. By the autumn of 1941, evasive routing of convoys due to Ultra meant that the U-boats were sinking far fewer merchantmen; and as one historian has put it, ‘Bletchley Park had gone from being stymied by maddening cryptanalytic obstacles to being overwhelmed by its own success.’11 Yet it was not to last long.

  Although the Abwehr set up regular investigations into the security of Enigma, and the commander of the U-boat branch of the German Navy, Karl Dönitz, had himself questioned whether it could have been broken, the Germans only continued to refine the existing machine settings rather than institute a brand-new communications system. Geheimschreiber, for example, was a non-Morse cipher that had up to ten rotary wheels, against the Enigma’s maximum of five. Its product was codenamed Fish at Bletchley and was far harder to crack, but it was not universally employed. Had a suspicious Reich turned to it instead of relying upon Enigma, the story of the Second World War might have been very different. Sir Harry Hinsley, the historian of British wartime intelligence, calculated that without Ultra the Normandy landings could not have been launched until 1946 at the earliest.12

  Although the Allies could not be seen to rely on it too much, for fear that the Germans would realize it had been compromised, information gleaned from Ultra was used to great advantage at many key moments of the war – for example, it brought about the battle off Cape Matapan, enabled the sinkings of the Bismarck and Scharnhorst, disclosed Rommel’s weaknesses and shortages prior to El Alamein, simplified Montgomery’s advance into Tunisia in March 1943, made the planning for the invasions of Sicily and southern France much easier, exposed the whereabouts of German divisions before D-Day and revealed Hitler’s orders for a counter-attack at Falaise in August 1944. (The day before the Mediterranean battle of Cape Matapan, Admiral Cunningham strode ashore at Alexandria carrying his golf clubs, so as to lull the suspicions of the Japanese consul-general there. The next day, 28 March 1941, he sank three Italian destroyers and two cruisers whose whereabouts and intentions he knew from the Ultra decrypts he had received.) 13 Yet it was undoubtedly in the battle of the Atlantic that Ultra was put to greatest use. Hut 8 of Bletchley Park succeeded in decoding about 1.12 million of the 1.55 million Kriegsmarine signals that were intercepted during the Second World War.

  The battle of the Atlantic has been described as ‘one that really did threaten Britain’s survival just as surely as would panzer divisions roaming through the Home Counties’.14 In his memoirs Churchill wrote: ‘The only thing that ever really frightened me during the war was the U-boat peril… I was even more anxious about this battle than I had been about the glorious air fight called the Battle of Britain.’15 The UK had to import two-thirds of all her food during the war, 30 per cent of her iron ore, 80 per cent of her soft timber and wool, 90 per cent of her copper and bauxite, 95 per cent of her petroleum products and 100 per cent of her rubber and chrome.16 It is a moot point whether, in the event of the U-boats closing down her imports completely, Britain’s armaments industry would have ground to a halt before or after mass starvation struck every urbanized area. Yet that was unlikely to happen, for Hitler saw only too late the potential war-winning capacity of the U-boat, despite its almost bringing Britain to her knees in 1917. If the Nazis had started the war with as many submarines operational in September 1939 as they had in March 1945 – that is, 463 instead of only 43 – they might have won it. As it was, they did not come close to strangling British imports at any point, and once they had invaded Russia instead of the Middle East, and declared war against the United States, Britain was effectively safe from a naval and supply point of view. ‘The decisive point in warfare against England lies in attacking her merchant shipping in the Atlantic,’ Dönitz had long argued, but he believed he needed a minimum of 300 U-boats to be sure of victory, and he had less than one-sixth of that total in 1939.17 Once Hitler finally recognized their potential, a huge increase in U-boat production took place, but it was too late to win the all-important battle of the Atlantic. With only one-third of submarines operational at any one time, the others needing crew training and boat refitting, a massive building effort should have been instituted by Hitler by 1937 at the very latest, but he missed the opportunity.

  Churchill agreed with Dönitz’s thesis, writing after the war: ‘The U-boat attack was our worst evil. It would have been wise for the Germans to stake all on it.’18 However, Dönitz was not the important figure when war broke out that he later became (indeed he ended the war as Führer of Germany). Although he was Führer der Untersee-boote at the outbreak of war, he only held the same rank as a cruiser captain.19 Born in September 1891 at Grünau near Berlin, he served as first watch officer under the U-boat ace Walter Forstmann in the Great War, before being given his own command in the Mediterranean, only for his boat to surface out of control while attacking a convoy. As a POW aboard a British cruiser in Gibraltar, he witnessed the armistice celebrations on the Rock in November 1918, and gestured to the ship’s captain at all the flags of the Allied powers flying from the ships, before asking what pleasure could be gained ‘from a victory attained with the whole world as allies’. The Briton replied pathetically, ‘Yes, it’s very curious,’ thus missing out on teaching Dönitz a valuable lesson about what would happen when Germany declared war against a global alliance.20

  Karl Dönitz became a proponent of submarine warfare long before the moment when the Reich threw off its restraints under the Versailles Treaty, which banned it from having any submarines. Under the 1935 London Treaty, all signatories, including Germany, agreed to build a submarine fleet of no more than 52,700 tons, with no individual boat of more than 2,000 tons, but Germany used Spanish and Finnish yards to circumvent these restrictions. Yet Germany needed a tonnage vastly larger than she was building even illegally in order to destroy British maritime trade in wartime; and even if Dönitz had held greater sway in the German Naval Ministry than he actually did, it would probably have made little difference, as Admiral Erich Raeder was also making these arguments, with only intermittent interest from Hitler. ‘On land I am a hero,’ the Führer once said, ‘but at sea I am a coward.’21

  Hitler was fascinated by the great surface ships such as the battleships Bismarck and Tirpitz, the pocket battleships Deutschland, Admiral Graf Spee and Admiral Scheer, the battle cruisers Scharnhorst and Gneisenau and the heavy cruiser Prinz Eugen, but he understood very little of naval strategy and the influence of sea-power. He certainly failed to spot the potential of a massive U-boat campaign, and largely ignored his admirals’ pleas for more ships and submarines during 1940, preferring to concentrate resources on the Wehrmacht and Luftwaffe. It was to be one of his greatest blunders of the war.

  The deeply religious, handsome Dr Erich Raeder was born in Hamburg, the son of a languages teacher. He had been the navigation officer aboard the Kaiser’s yacht Hohenzollern, then served as a Staff officer under Admiral von Hipper during the Great War. He took an honours doctorate from Kiel University afterwards, writing a dissertation on cruiser warfare that he later published as a book. Naval chief of staff from 1928 and commander-in-chief of the Kriegsmarine from 1935, Raeder’s naval building programme, Plan Z, presupposed a war that began in 1944, which implies very poor co-ordination with the Führer. When it actually began five years too early, the German Navy did not yet have the balance – specifically in the areas of aircraft carriers and U-boats – to deliver victory against the Royal Navy. On the outbreak of war, Germany had only two modern battle cruisers – Scharnhorst and Gneisenau – three pocket battleships, two heavy cruisers, six light cruisers, twenty-two destroyers and only forty-three submarines, so on 24 September 1939 Raeder spent several hours trying to persuade the Führer of the attractions of a major, immediate U-boat building programme.22 Hitler said that he sympathized, but the necessary manpower and steel were not subsequently allotted to the Kriegsmarine in anything
like the quantities required.

  After a series of sharp engagements against the Royal Navy, by the end of 1940 Germany only had twenty-two U-boats left, and only twenty were built between the outbreak of war and the summer of 1940. Yet the twenty-five U-boats that were operating in the Atlantic by then had sunk no less than 680,000 tons between them.23 On 17 October 1940 a group of seven U-boats attacked Convoy SC-7 near Rockall, which numbered thirty-four merchantmen but had only four escorts. No fewer than seventeen ships were sunk, and no U-boat was damaged. U-boat captain Otto Kretschmer chalked up sinkings in the Atlantic that were to amount to more than a quarter of a million tons. As a result, Hitler slowly recognized the submarines’ potential and on 6 February 1941 he issued Führer Directive No. 23, which emphasized that ‘The wider employment of submarines… can bring about the collapse of English resistance within the foreseeable future… It must therefore be the aim of our further operations… to concentrate all weapons of air and sea warfare against enemy imports… The sinking of merchantmen is more important than attack on enemy warships.’24 Yet by then he was already deep into the planning stage for Operation Barbarossa, which was severely to undermine the U-boat offensive. Had he concentrated on knocking Britain out of the war first, he could then have turned eastwards at his leisure, with all the forces of the Reich and no prospect of having to draw off forces into Africa or the Mediterranean, and no aid coming to Russia from Britain either.

  The Kondor was the Focke-Wulf 200 maritime reconnaissance bomber and had a range of up to 2,200 miles; it carried a 4,626-pound bomb load, flew at 152mph but lacked significant armour. It could be an invaluable spotter for U-boats, but when Dönitz asked Göring for more Kondors he was refused them, and for all the inspiring language of Directive No. 23 he had to rely on the twelve Kondors of Squadron KG40. These were nothing like enough, and as he later noted: ‘Here the flaw in the conduct of the war was revealed with painful clarity.’25 The call-up of 25,000 skilled dockyard workers to fight on the Eastern Front was another blow to Raeder and Dönitz, and when two years later Hitler announced the total scrapping of the capital-shipbuilding programme, Raeder resigned, to be replaced by Dönitz.