From our archives...
October 1943 : Not all our own way
The breakout from the Salerno beachhead and the advance to capture Naples created a false sense that the capture of Rome, some 100 miles to the North, would soon be achieved. But the battle to cross the Volturno soon showed that relatively small German forces, aided by the mountains and rivers, were going to be able to delay and make expensive the Allied advance northwards. The swift German reaction to the British recapture of the islands like Cos in the Dodecanese showed the Germans were far from beaten in the Mediterranean. The foiled British attempts to establish a strong foothold in the Eastern Mediterranean had the unfortunate side effect that the brilliant deception campaign, which had fooled Hitler into believing our main attack was coming there, was now spoiled. But Hitler never ceased to expect an Allied thrust in that part of the Mediterranean theatre, and the Yugoslav partisans were now mounting a remarkably successful campaign that cost the Germans very considerable forces to contain. Though some of the RAF raids on Europe were now proving very successful, such as the bombing of the aircraft plants at Kassel on 22nd October, the very high cost of the USAAF daylight raid on Schweinfurt on 14th October had forced them to abandon raids until suitable long-range fighter aircraft were available next spring. Of the 228 American bombers used that day, 62 aircraft were lost and little damage was done to the ball-bearing factories. The Russian offensives in the South were now beginning to falter as they out- run their supplies. But they had recaptured great areas of land, had cut off the Crimea, and, in proof of their ever increasing sophistication, had secured a number of major bridgeheads across the Dnepr river line before halting to regroup. The Russians had a considerable team at their headquarters who studied each campaign and spread the lessons, so their commanders were now becoming ever more expert and experienced. The Germans had exaggerated the number of Russians involved in these 1943 offensives after the defeat of their own offensive at Kursk, but now had to face an enemy who had learnt all too well from them the secrets of mobile warfare. Russian production of weapons was out-classing Germany’s, even though Albert Speer had at last mobilised their labour force in addition to using much slave labour.
The Heroism of Individuals. The dark clouds of the horrors of war often seem to have a silver lining in the selfless heroism of individuals. On 29th September as the Germans attempt to arrest and deport them, almost all Denmark’s Jews, including the great physicist Neil Bohr, are smuggled across the water by Danish fishermen to the safety of neutral Sweden. On 3rd October, in response to an appeal in an underground newspaper, 3,000 Athenian Jews are given shelter, some in the home of Princess Andrew of Greece whose son, Prince Philip, is serving in the Royal Navy. On the 23rd October at Auschwitz, in one of the very few recorded revolts, when ordered to undress in the gas-chambers a former Warsaw dancer named Horowitz threw her shoe at the guard, seized his revolver and shot him. Other women joined in the ensuing riot, the SS guards fled but returned and removed the women individually to shoot them. In the Pacific on 27th October a young Lieutenant, John F. Kennedy, in charge of a small torpedo boat, personally rescues the eight-man crew from drowning when his craft is wrecked on a reef, and is back in action against the Japanese three days later.
The Milch Cows and the Atlantic Battle. On 8th October 1943 the Allies occupy the Azores, with the agreement of the Portuguese Government, in itself evidence of the growing certainty in the neutral governments that Germany is going to lose the war. This closes the last gap in the air coverage of the Atlantic. (It was known from Axis diplomatic and Abwehr decrypts that the Germans were expecting this to happen, but not when). During the summer months the US Navy has been attacking at their rendezvous points the ‘Milch Cow’ U-boats - the large supply U-boats that could double the time the attack U-boats could stay on patrol. In the early years of the war, the Germans had employed surface supply boats, but these proved very vulnerable to Allied attacks and had been abandoned, being replaced by the milch cows. The German U-boat command radioed rendezvous point instructions often some two weeks before the date for the re-supply operation, so BP has plenty of time to decrypt the messages, even when they are encrypted in the double encyphered Enigma ‘ Offizier’ class of key and use disguised map references. (Leslie Yoxall, Joan Murray and Rolf Noskwith in Hut 8 had first mastered this class of key in 1941/42). Radio finger-printing (RFP) could distinguish the transmissions of these large supply U- boats from those of the normal attack U-boats. However, after the sinking in June 1941of most of the surface supply boats sent out to service the ill-fated Bismarck, BP had guessed the Germans would instigate an investigation though the Germans had rejected the idea that the losses were due to the British reading Enigma messages - as had been the case. So the British were very reluctant to allow attacks on the milch cows except in transit to their rendezvous points. In the year until May 1943 the milch cows had refuelled U- boats some 390 times without being disturbed though three had been sunk on passage, leaving nine on station and three still to reach their stations. Cmdr Kenneth Knowles, the Director of the US equivalent of the Admiralty’s Operational Intelligence Centre commented ‘The British were more clever in the use of Ultra; the US more daring.’ But he added ‘But then they had so much more to lose’. In June 1943 aircraft from the US escort carrier USS Brogue attacked and sunk the milch cow U-118. Decrypts showing the emergency this caused for the U-boats persuaded the US to mount a campaign against the milch cows, and the British reluctantly agreed to join in, partly because the ever-increasing Allied air surveillance now provided good cover for their discovery. Often aided by Enigma Intelligence, the US sank four in July and by the end of the year the US escort carriers and Coastal Command and British surface ships had sunk six more. At least eleven operational U-boats were also sunk close to the refuelling points. [By July 1944, 16 of the 17 supply U-boats that had been built were sunk]. Centimetric ASV radar in Coastal Command aircraft from March 1943 helped to increase the number of U-boat sightings, and forced them to travel submerged except for short periods for battery charging. Admiral Dönitz’s tactics of remaining on the surface to fight when detected and travelling in groups to increase their anti-aircraft fire-power only aided the Allied airborne offensive. Early warning of U-boat sailings is now being obtained regularly from the Enigma Dolphin Home Waters keys. Though the time to decrypt the U-boat Shark key Enigma messages is now reducing to an average of 24 hours, sightings owe much to the skill and patience of Coastal Command’s aircrew. But the Enigma decrypts are now of enormous value to the Operational Intelligence Centre.
The German Navy Suspicions over Enigma. When Dönitz resumed the U-boat offensive against the North Atlantic convoys in mid September it was with new weapons such as the acoustic torpedo and a new apparatus for detecting radar signals. The antidote for the acoustic torpedo, ‘Foxer’ a towed raft generating much noise, was ready to deploy and no ship equipped with it was ever sunk. After the initial attack, the U-boat offensive causes few Allied losses and high U-boat casualties. Dönitz said in his memoirs that ‘the Allies could see my cards without me being able to get so much as a glimpse of theirs’. It was not to be expected that the assault on the milch cows at their rendezvous sites, especially the attacks on ten refuelling rendezvous points in one week in August 1943, would go without suspicion in the HQ of the German Navy. Until the Admiralty introduced Naval Cypher No.5 on 10th June 1943 the German Navy’s B-Dienst (BdU) had been reading many of the British signals to the convoys. These signals invariably referred to the U-boat position information as being derived from D/F, radio direction finding. (It is remarkable and a great tribute to those involved that no single Admiralty message intercepted by BdU ever directly gave away the actual source of the information, unlike the German navy for their messages to the U-boats soon revealed to BP, once Shark was being read, that the Germans were reading our messages). To further increase their suspicions, in late March 1943 the BdU had decrypted a message from the US Navy that gave the position of a particular Wolfpack patrol line derived from ‘inaccurate D/F’. But BdU had known that this Wolfpack had not yet sent out any radio signals. Now the Abwehr in Switzerland has received a report that ‘A special office in England has dealt exclusively with solving German codes. It has succeeded for some months in reading all orders by the German Navy HQ to U-boat commanders, which has very considerably helped the hunt against the U-boats’. This message came via the Swiss Intelligence Service from what was said to be a Swiss-American in an important position in the US Navy Department in Washington. (It seems to be accepted that such a spy existed). However, once again the German Navy experts declared that ‘At present no possible way of solving the Enigma plugboard combinations within a reasonable time is known, even with the maximum amount of labour’. They were also confident that their emergency procedure called Stichwort, for over-riding a key-list when they suspected that it had been captured, was unbreakable even using ‘extensive mechanisation’. In practice it was readily broken at BP. Once again the Germans had set aside their suspicions that the Allies must be reading Enigma; they had found no evidence in the intercepted British messages.
Hut 8 Progress: The Biscay Weather Crib. In September 1943, the amount of available bombe time in the UK and US reached the point when it was no longer sensible to work on the Banburismus technique to reduce the wheel orders that need to be tested on the bombes. This was abandoned with very considerable regret by the staff of Hut 8 (now without Alan Turing) who had come to enjoy the daily intellectual struggle. On 1st July 1943 the Germans had introduced a new reflector (Caesar) and a new fourth wheel (Gamma) to the 4-wheel Enigma. Hut 8 knew these were coming from decrypts, and Hugh Alexander, the head of Hut 8, subsequently commented that in order to work out the wiring of these ‘all we needed was a long re-encypherment and a good deal of patience; both of these commodities were in reasonable supply’. Richard Pendered, following Knox and Turing, had developed a method for determining the wiring. They had to wait a few weeks before they obtained the ‘kiss’ from Dolphin, and then were able rapidly to get back into Shark. (‘Kisses’ for Shark from Dolphin were quite common, if only because the U-boats in the waters north of Norway remained on Dolphin). However the choice of reflector and its associated special thin wheel meant that it seemed the amount of bombe time needed would increase by four. However ‘the breaking of a few July days revealed the gratifying fact that the combined Caesar- Gamma remained in force for a full month’. Now as re-encypherments mounted and cribs improved so did the regularity and speed of breaking Dolphin and Shark; on 24th October the ‘Biscay Weather’ crib came into effect. This was a station that put out regular weather reports. It had been using good security procedures being unpredictable in phraseology, but ‘miraculously’ from now-on it became highly predictable, with much of the text repeating from message to message – an ideal crib! Apparently a German operator there always started his reports with WETTERVORHERSAGEBISKAYA. [In January 1944, much to their dismay Hut 8 intercepted a message in Shark from the German Naval Communications Security Service who had spotted the possible crib (they spotted most of them in due time) objected to the lax security, and complained about the repeat of this regular message on the Ireland frequency. However, the sole effect of this reproof seems to have been that, from then on, the weather station sent a separate version on the Ireland frequency, so providing another excellent crib! This crib lasted until June 1944, when no doubt the weather station was disturbed by the aftermath of the Allied landings]. With the decline of the work-load Hugh thinned out his team, reducing his number of cryptographers from ten to seven; Geoffrey Charlesworth went off to join Peter Twinn’s ISK section working on Abwehr Enigma; Jack Good and Shaun Wylie joined the Newmanry where they were both to do great work. (The Newmanry had just moved into the newly opened Block F along with the Testery). Hugh Alexander records that ‘except for Turing, no-one made a bigger contribution to the success of Hut 8 than Shaun Wylie; he was astonishingly quick and resourceful and contributed to theory and practice in a number of different directions’. Now Hut 8 had become the complete master of the vital U-boat Enigma key, Shark. 12th September 1943 was the last day when Hut 8 and their colleagues in OP-20-G failed to get Shark out; thereafter they broke it everyday until the end of the war. At about this time Admiral Dönitz sent a signal to his U-boats instructing them ‘Do not report too much bad news, so as not to depress the other boats’.
The Japanese Codebreaking Scene. In the autumn of 1943 BP stepped up the attack on Japanese codes, partly fed by teams who had been on Italian codes, partly by recruits coming off the Bedford six-month courses and from the London University S.O.A.S courses. In October a Japanese Air Intelligence sub-section headed by Joe Hooper is set-up in Block F to which other Japanese Sections now move. The Hut 7 team working on Japanese navy material is at last allocated more time on the Block C Hollerith equipment. The US are sometimes failing to honour the agreement to keep BP informed of their breaks into the Japanese codebooks and the resulting Intelligence, leading to these increases by BP. In September the outstation at Kilindini returned to Colombo where radio reception is much better and is reinforced from BP by more codebreakers and Wrens. It becomes known as HMS Anderson from the name of the golf course where the Centre is set-up.
The Bletchley Park Trust welcomes the preparation of these notes, but the authors are responsible for the statements and the views expressed.
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Do you have any information regarding the following question.
'Does anyone know where there is an account of the spy in the Navy Department (some people say in the White House) who leaked the Enigma secret to the Swiss? Did BP know of the existence of this spy - perhaps from Abwehr decrypts?'