by Max Hastings
Two thousand men and women served in the Naval Intelligence Division, among whom Admiral John Godfrey’s personal staff of fifteen clustered in the Admiralty’s Room 39. This was formally known as ‘NID17’, flag bridge of the intelligence war at sea, with its big westerly windows looking down on the Downing Street garden, the Foreign Office, the lake in St James’s Park, and Horse Guards Parade, the last disfigured by wartime clutter – barrage balloons, vehicles, temporary hutments. Donald McLachlan, one of Godfrey’s wartime staff, admired his chief, but understood why others were galled by him: ‘Like the driver of a sports car in a traffic queue, he saw no danger or discourtesy in acceleration.’ Godfrey’s impatience and irascibility prompted his replacement at the end of 1942, though the machine he created remained almost unchanged until the end of the war.
Outside the admiral’s green baize door sat his personal assistant, the dashing former journalist Commander Ian Fleming. McLachlan again: ‘if not the wisest of the staff in Room 39, the most vivid … His gift was much less for the analysis and weighing of intelligence than for running things and for drafting. He was a skilled fixer and a vigorous showman … a giant among name-droppers.’ The NID also employed writers and historians including Hilary Saunders, William Plomer and Charles Morgan; an art historian who handled PoW interrogation reports, Charles Mitchell; and the former head of Thomas Cook’s West End office, who ran the Scandinavian section. Room 39 was known to the ‘secret ladies’ and typists as ‘the Zoo’.
McLachlan itemised in order of importance the material from seventeen sources which was collated and reviewed by Godfrey’s staff. Unsurprisingly, the list was headed by decrypted enemy wireless traffic: until the end of 1943 Admiral Karl Dönitz and his subordinates ashore sought to micro-manage Germany’s U-boat campaign, and thus constantly exchanged signals with captains at sea, much to the advantage of the British. Thereafter in the roll call of intelligence sources followed captured documents; bearings on enemy shipping secured by ‘Huff-Duff’; intercepted voice messages; air photographs; ship sightings by aircraft; information from agents or friendly secret services; PoW interrogations; wireless traffic analysis; enemy communiqués; hints from intercepted civilian correspondence; topographical and technical information from open sources; friendly and neutral observers; tactical information gathered during operations at sea; sightings by merchant ships and coast-watchers; intelligence forwarded from other services; instructions from enemy intelligence organisations to double agents under British control. All material was graded in reliability and importance, from ‘A1’ to ‘D5’.
There was incessant, fractious and sometimes fierce argument about how far protection of the Ultra secret should be allowed to constrain operations against the enemy. On 11 March 1942 C-in-C Plymouth wrote to Godfrey, as DNI, complaining that information about an enemy vessel that was being towed to Cherbourg, and about an escorted German tanker on passage, had been in British hands in time to attack them, but reached operational commanders ten days late. Admiral of the Fleet Sir Charles Forbes – known to his own service as ‘Wrong Way’ Forbes since he shifted the Home Fleet beyond reach of Norwegian waters just before the April 1940 German invasion – fulminated: ‘The intense secrecy which shrouds all information conveyed by “Ultra” messages has been found to militate against the useful employment of this information for operational purposes. There is, indeed, a tendency to place the claims of security before the claims of offensive action … I do not think it can be too strongly emphasised that however secret may be the sources from which intelligence is obtained, such intelligence can never be an end in itself, and if it does not lead to action it is valueless.’
Forbes’s letter is significant, because it highlights the daily dilemmas faced by the guardians of Ultra. Moreover, it illustrates how wisely and well British and most – though by no means all – American officers served the Allied war effort, by resisting many temptations to exploit decrypts, in order that they might protect the Allies’ wider interests in the secret war. In the latter half of 1942, when air interdiction of Rommel’s Mediterranean supply lines attained devastating effectiveness, guided by Ultra, almost every RAF attack was preceded by a reconnaissance overflight, to mask the source of British knowledge.
If Bletchley’s output was the most important source of intelligence, supplementary aids were indispensable. Sigint could not be relied upon to provide – for instance – warning of sailings of German capital ships, often screened by wireless silence. Norwegian agents monitoring the fjord anchorages of Tirpitz and its kind provided vital alerts about whether they were preparing to put to sea or had done so. A naval intelligence officer wrote: ‘So reliable was this service … that the OIC in London had complete faith in [the agents’] accuracy and regularity.’ Here was something MI6 did well. Meanwhile, aerial reconnaissance was invaluable when the weather made this practicable, though it remained an inexact science, especially if naval intelligence officers were obliged to rely on a pilot’s remembered glimpses, rather than on photographs which could be subjected to expert interpretation. It was hard for aircrew, thousands of feet up, to distinguish between a battleship, a heavy cruiser and a big destroyer. In July 1942 a Luftwaffe pilot’s sighting of a single British plane in the sky off Norway deterred the Germans from dispatching Tirpitz against PQ17. The airman reported seeing a carrier aircraft. In reality this had been a mere floatplane, but the Kriegsmarine declined the risk that a Royal Navy carrier group might be within range of their precious monster.
In the early war years British technical knowledge about U-boats was poor, partly because the NID lacked sophisticated interrogators who knew what questions to ask prisoners. By 1942, matters had improved: U-boat crewmen in British camps revealed the existence of the Pillenwerfer, the bubble-ejection technique for foxing Asdic detectors; also details of German torpedoes and search-receivers for radar transmissions. Interrogators learned – as did their Luftwaffe counterparts quizzing Allied airmen – to confound prisoners by showing off knowledge of their domestic affairs, for instance the charms of the red-haired waitress at Lorient’s Café de Rennes. A problem persisted, that the Royal Navy was unwilling to believe that technology its own ships lacked might work for the enemy – several U-boat refinements, and big 5.9-inch guns mounted on destroyers.
Some interrogators favoured offering relatively lavish hospitality to celebrity prisoners who might provide important information. In October 1944 the director of intelligence threw up his hands in horror when he learned that his officers had spent £2 on wining and dining a U-boat captain. The DNI issued a formal warning against ‘entertaining at the Ritz and the purchase of considerable quantities of gin. If these facts became known, there might be good cause for scandal. Furthermore, I and many others are quite unable to enjoy these luxuries, and it is out of all proportion that our enemies should.’ The interrogator responded impenitently that it seemed worth £2 of taxpayers’ money to convince a sceptical Nazi that the Ritz was still standing.
Perversely, even as the tide of war turned decisively against the Germans, some of Dönitz’s crewmen in Allied hands became stubbornly security-conscious. On 12 March 1944 the DNI briefed the First Sea Lord on recent PoW interrogations. Some 70 per cent of U-boat crews by then accepted that the war was lost, and 25 per cent would frankly avow this to a British officer. But crews were better trained to resist interrogation; even at this late hour for the Nazi empire, ‘there is a general belief that those who divulge information will be punished after the war’. When censors discovered that captured U-boat crewmen were using a simple code to convey sensitive material in letters home to Germany, the traffic was allowed to continue, in hopes that the NID would find uses for such disclosures.
Next door to the Admiralty, the Operational Intelligence Centre was located in the new Citadel building, a dank concrete mass, much overcrowded, whose inmates suffered from chronic colds and viral infections. The OIC’s surface-ship section, run by Commander Norman Denning, took centre stage in
British naval operations during such crises as the pursuit of the Bismarck, the ‘Channel Dash’ and the Arctic agony of Convoy PQ17. During hours and days of intense debate and harsh decision-making, the First Sea Lord and his acolytes became frequent visitors to the OIC. In the early war years there were persistent delays in implementing operational decisions following the receipt of decrypts. The Far East Combined Bureau, Bletchley’s Singapore out-station thereafter evacuated to Colombo, broke Japanese signals reporting the sighting of Prince of Wales and Repulse, as well as the enemy’s attack orders, four hours before the first bombs and torpedoes struck the great warships. But Admiral Tom Phillips, on Prince of Wales’s flag bridge, learned of this only when the Japanese were already overhead and his doom was sealed. Fortunately for the Royal Navy, the transmission of such urgent material was much accelerated thereafter.
The tactical war at sea was more powerfully influenced by sigint than the land campaigns, partly because convoys and submarines travelled more slowly than tanks. Given that decryption of enemy signals required at best hours, and sometimes days, its fruits were more likely to reach commanders in time to trigger an operational response on the ocean than was usually possible on a land battlefield. On many days between 1941 and 1945, the most important place in British naval headquarters was its Submarine Tracking Room. There, Commander Richard Hall – son of ‘Blinker’ – gave orders to reroute convoys, in accordance with the latest appreciations of U-boat positions made by the Room’s overlord, the immensely respected Commander Rodger Winn. The Room’s wry but deadly earnest motto was ‘Never the twain shall meet.’ Winn himself, cursed since childhood polio by a limp and a twisted spine, was a remarkable personality, who treated senior officers with suitable respect, like the former barrister he was, in the company of a judge, such as he later became. Yet he never failed to assert his own convictions. His most striking characteristic, which distinguished him from many peers on both sides of the war, was moral courage. He drove his staff hard, rebuked mistakes with a biting tongue, and insisted that the Tracking Room delivered a single collective view on every issue.
Informality nonetheless prevailed: colleagues were treated as equals, heedless of rank. Civilian watchkeepers and researchers maintained the Room’s signal log and compiled its records and statistics. On the walls, graphs recorded peaks and troughs of merchant-ship and U-boat sinkings, together with the progress of new construction. The Room’s hub was an 8ft x 8ft table, on which was mounted a chart of the North Atlantic. Here, for up to fourteen hours a day, Winn or his deputy sat chin in hand, plotting distances and calculating speeds and angles, with one eye on the teleprinter that spasmodically clattered into life, disgorging flashes from Bletchley. On the plot, the limits of Allied air cover were shown by red arc lines painted across the ocean. U-boat positions were indicated by coloured pins: red for a firm fix, white for a sighting, blue for a DF bearing.
Sometimes during a U-boat wolf-pack attack, the Royal Navy’s escorts might secure up to forty DF ‘fixes’ in an hour on Dönitz’s submarines. To secure a reasonably accurate bearing, a ship needed to be within forty and fifty miles of the U-boat’s transmissions; to get a precise one, ten to fifteen miles. In good weather, a convoy might average a speed of seven to nine knots. Though a surfaced U-boat could manage eleven knots, its submerged speed slowed to just two or three. Thus it was that Allied aircraft exercised a critical influence as long as convoys sailed within their sweep radius, by forcing submarines to dive even if air-dropped depth-charges failed to sink them. Since these naval battles took place in relatively slow motion, diverting the course of a convoy could render it impossible for Dönitz’s hunters to catch up.
Every morning Winn or his deputy held a telephone conference with the C-in-C Western Approaches in Liverpool, and the chief of staff to the C-in-C of RAF Coastal Command, during which Winn described the main events of the preceding night. At midday Hall dispatched a four-page situation report to Churchill’s War Room. Once a week, the entire table plot from the Tracking Room was transferred to new chart sheets, as the old ones became pepper-potted with pinpricks. A colleague wrote of Winn’s ‘uncanny flair for guessing a U-boat’s behaviour’. During running convoy battles that persisted through several days and nights, ‘the intense intellectual labour that went into this battle of tactics was tolerable to the human beings engaged only if it became for them virtually like a game of chess or bridge … they had to keep in check any leap of imagination which would have pictured in terms of appalling human suffering their failure say, to extricate a tanker convoy from the assailing pack. Otherwise the strain would have been too great.’ Thus, they were once obliged to preserve an icy calm while one of their own former colleagues in the Tracking Room, a certain Commander Boyle, led a convoy from Trinidad of which eleven tankers were sunk one by one, until just one ship reached port.
In December 1942, Winn came under immense pressure to detach from a southbound Atlantic convoy the White Star liner Ceramic, carrying airfield specialists, because these men were urgently needed at Takoradi in West Africa. For four days he refused, asserting his conviction that the Germans were tracking the convoy and would soon attack. Then he yielded to the insistence of the Ministry of Shipping. Ceramic raced ahead – and was sunk with only a single survivor. By 1943, so great was respect for Winn’s judgement that an Admiralty standing order was introduced that no ship or convoy should be routed against his advice. Yet so great was the strain imposed by his responsibilities that for a month the Commander had to quit his post, after succumbing to nervous exhaustion.
So much has been written about Bletchley’s triumph in breaking the U-boat codes – which was real enough – that the story of the Battle of the Atlantic has become distorted. The matching achievement of the Kriegsmarine’s B-Dienst intelligence service deserves more notice. For about a year, from July 1942 to June 1943, though with some intermissions and delays, Dönitz’s codebreakers provided the U-boat command with an extraordinary wealth of information about convoy movements, which made almost as important a contribution to soaring Allied shipping losses as did the deadly coincidence of BP’s inability to break the Shark cipher for much of the same period.
U-boat operations were controlled by a tightly-knit group of five staff officers around Dönitz, at BdU headquarters located successively in Lorient, Paris, and – from January 1943 – Berlin. Among the most important personalities was the signals specialist Kapitän zur See Hans Meckel. The loss of every submarine was subjected to meticulous inquiry, not least to consider whether any breach of security might have contributed to an Allied sinking. The B-Dienst, headed by Kapitän zur See Heinz Bonatz, was based in naval headquarters, situated like the Abwehr in Berlin’s Tirpitzüfer, and grew to a strength of 6,000 men and women. Teleprinters disgorged signals from listening stations all over Europe, of which the largest was in Holland. Its codebreakers, led by the veteran former naval wireless-operator Wilhelm Tranow, benefited from the fact that Dönitz was one of the few German senior officers of any service to take intelligence seriously. Like his Allied counterparts, he recognised that the first imperative of the war at sea was to locate the enemy.
During the spring and summer of 1940, the B-Dienst reckoned to read around 2,000 British messages a month, though this declined steeply in August after the Royal Navy changed its codes. From 1940 until 1944, Bonatz’s men achieved reasonably regular breaks into the Merchant Navy code. After capturing its latest version, ‘Mersigs II’, in March 1942, they consistently penetrated convoy signals, allotting names to different varieties of British traffic in the same fashion as did Bletchley to German ones: Köln, Frankfurt, München Blau, München Rot. At this time also they began to make effective use of IBM-type punch-card technology.
One of the most serious wartime failures of Bletchley Park was that its small cipher security section failed for many months to recognise and alert the Admiralty to the vulnerability of some of its codes, despite several requests for advice and assistance from the nav
al officer responsible. The Germans read the signals of New York’s harbour captain, who gave the composition and often course updates of eastbound convoys, even when rerouted by Rodger Winn. The B-Dienst’s break into the Royal Navy’s Cypher No. 3 was not comprehensive: many messages were read only after an interval of days, and only about one in ten became available fast enough to concentrate U-boats. But thanks to sigint, Dönitz’s general view of Allied operations was strikingly well-informed.
The post-war American study of German naval communications intelligence, based on exhaustive interrogations of personnel and study of captured documents, in this case the B-Dienst’s, concluded: ‘The enemy possessed at all times a reasonably clear picture of Atlantic convoys with varying degrees of accuracy as to the routes and day-by-day plotting … Convoy diversions were sometimes learned from decryption in time to re-arrange U-boat patrol lines accordingly … The most complete single statement of German convoy intelligence ever seen here in German naval traffic came in a series of messages … in December 1943 and January 1944. These messages apparently reproduced the [Allies’] current convoy chart for the North Atlantic … The convoys then at sea were correctly identified both by designators and numbers, and accurate information given on convoy cycles, speeds and general routing.’
The American study makes abundantly clear that the wireless war at sea was by no means one-sided. British sins of omission and commission both at the Admiralty and Bletchley cost ships and lives. The B-Dienst had codebreakers of considerable skill, if not quite in the class of Hut 8’s people. In the ten days 9–19 March 1943, during the period when the Kriegsmarine was winning the sigint war against the Royal Navy, four convoys – SC121, HX228, SC122 and HX229 – each lost one in five of its ships, a disastrous attrition rate. Yet actions or lapses sometimes had perverse consequences. This very failure of the Royal Navy’s code security conferred a priceless boon on the Allied cause, albeit at heavy cost. At intervals throughout the war, and initially as early as 1941, Dönitz entertained serious suspicions that Enigma had been penetrated. On 28 September, a British submarine ambushed U-67 and U-111 at a rendezvous near the Cape Verde islands, off Senegal. Its torpedoes missed, and it was itself rammed by a third U-boat on the scene, but the admiral said when told of this dramatic incident: ‘A British submarine does not appear by chance in such a remote place,’ and launched a major inquiry. Yet this concluded that ‘the more important ciphers do not appear to have been compromised’. A second investigation in February 1943 reached the same conclusion, once again reassured by the vulnerability of British codes, which persisted until June. If the Royal Navy had the power to read the German hand, its chiefs would surely have closed this costly hole.