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September 1943 : Germany Stands Alone

As the war enters its fifth year the problems facing Hitler begin to multiply. He was expecting the surrender of Italy, and responds remarkably fast to the Allied landings. But by turning his attention to taking over the territory that Mussolini had controlled, he makes it very difficult for his Generals in Russia to make a stand that will halt the Russian attacks in the south, refusing them resources he now wants for the defence of Western Europe. Despite the way the Allies almost stumble into the Italian campaign, for the first time their operations in the Mediterranean are having a very significant direct impact on the German operations on the Eastern front. The Russians are sweeping forward towards and over the Dnieper all along the Southern front, and the Germans have to evacuate the Caucasus. The bombing of the homeland adds to Hitler’s woes, though the scale of the losses by the USAF in its daylight raids are becoming insupportable, and the RAF seems incapable of repeating the havoc it had created in its raids on Hamburg. But the diversion of resources to the defence of the homeland means that Germany will now generally find itself unable to prevent the Allies from gaining overwhelming air superiority on the fighting fronts. The one glimmer of hope for Germany comes from its new high-technology weapons, such as the radio controlled bomb which is meeting with considerable success in the Mediterranean, and the acoustic torpedo which helps to make the re-entry of the U-boats to the North Atlantic this month look like a success, though neither were to fulfil their initial promise as the Allies soon deploy suitable counter-measures. It is said that Hitler was never told about the success that the new guided weapons at first achieved because Adolf Galland, commander of the Luftwaffe’s fighter wing, feared that if he knew, Hitler would divert funds from the development of manned fighters such as the coming generation of jet aircraft, into these unmanned weapons. The remarkable fighting ability of the German army, not least in defence, remains a major asset. But the fact that Bletchley Park is now providing the Allies with a window on the German plans and activities of virtually every German venture means that the Allies have a hidden asset of great worth, if only for minimising unwelcome surprise and casualties.

The Invasion of Italy. With the fall of Messina on 16th August the Allies turned to prepare the invasion of Italy. With the collapse of the Italians now seeming highly probable, the Americans, led by General Marshall, favoured an amphibious operation to capture Naples, followed by a rapid advance to Rome. Churchill, of course, was not satisfied with this, wanting to continue into the Po valley with the prospect of then advancing east into southern France or west into Austria; (anything to avoid the hazardous landings in Northern France). General Eisenhower decided to land Mark Clark’s Fifth US Army (6th US Corps and 10th British Corps) at Salerno, thirty miles south of Naples a week after Bernard Montgomery had invaded across the narrow Straits of Messina, which was carried out by the British Eighth Army on 3rd September, after a massive and quite unnecessary bombardment as the Germans had already withdrawn. Progress northwards was painfully slow, not so much because of the direct opposition of the Germans but because of their skilful use of mines and demolitions along the few mountain roads. Field-Marshal Kesselring had decided to make a staged withdrawal up Italy based on a succession of well-prepared defence lines running across the country. General Eisenhower, rather unwisely, announced the Italian surrender on the 8th September, nine hours before the Allied troops are due to land at Salerno. The Germans move very rapidly to disarm and take over from the Italians. Within two days most of the Italian forces have been disarmed and Rome occupied by the Germans; an Allied project to land the US 82nd Airborne Division to occupy Rome is abandoned. (On the Greek island of Cephalonia Italian troops resist being disarmed by the ruthless Germans; 1,646 are massacred, and the remaining 5,000 surrender but execution awaits them). Only the Italian fleet escapes, its main body sailing to Malta, and is escorted into Grand Harbour, Valletta. Their old adversary and the victor of the Battle of Cape Matapan, Admiral Andrew Cunningham, signals the Admiralty ‘Be pleased to inform their Lordships that the Italian Battle Fleet now lies at anchor under the guns of the fortress of Malta’. But even this escape is incomplete as, en route, one of the new German radio controlled armour piercing bombs, the FX-1400, is guided into the Italian flagship, the battleship Roma and she blows up with the loss of nearly all hands. The fact that BP had provided advanced information about the new weapon, and had warned that it was about to go into service, meant that its use should have come as no surprise to the Royal Navy, but it certainly did and at first it proved frightening in its effectiveness.

Operation Avalanche. General Kesselring knows the landings in the Bay of Salerno are coming, as the Allies are well aware from Abwehr Enigma decrypts, and he issues a warning on the 8th, a signal also rapidly decrypted by BP, so the Allies know the 16th Panzer Division will be awaiting the invasion forces. (The Allies also now know a minefield lies right in the planned path of their invasion convoys but delay until the last moment passing on the information for fear of exposing the source of the Intelligence). On the northern edge of the landings the two British infantry divisions are relatively experienced in battle, unlike the US divisions who General Mark Clarke chooses to land some 10 miles away to the south. Hardly surprisingly, the experienced Panzer Division tries to take advantage of this separation by driving to the coast to split the front. It nearly succeeds, being only just halted by naval guns. Taking a huge risk, the ageing battle-ships HMS Warspite and Valient steam into the fray close to the shore, along with several British and US smaller vessels. This firepower proves over-whelming, and after eight very perilous and hard fought days, the 16th Panzers, by now joined by elements of the 15th Panzer-Grenadier division, fall back as the forward elements of the Eighth Army approach on the 16th, somewhat belatedly, from the south. At the peak of the panic, Mark Clarke had been making plans to evacuate the beach-head, much to the disgust of his superiors and some of the more experienced British force leaders. This was the first time that the Allies had met a seriously opposed landing, and the experience hardly encouraged those like Churchill who dreaded the massacre that they feared might arise on D-day. As Salerno was at about the limit of range for the aircraft coming from Sicilian airfields, air supremacy established over the beachhead was, at best, fragile. The fleet auxiliary carriers, however, proved their worth when the land forces failed to capture the one airfield that had been a target for capture by the second day. The price paid by the navy was heavy, including severe damage to Warspite from another guided bomb, though she was just able to limp under tow to Malta. Two other ships were severely damaged by the bombs. Now the Allies can move northwards, but constantly meeting skilful and stubborn resistance as the Germans make a fighting withdrawal as they fall back to the Gothic line. The Allies enter Naples on 1st October to much rejoicing, which is soon to turn to tears in the worsening weather and the endless battles over mountain ridges and flooded rivers. It seems that the US leaders were right when they feared that forces that should have been made available for the coming D-day landings and campaign were to become bogged down in this peripheral campaign and difficult fighting terrain of Italy. But of course German forces that could have been available to stem the Russian advances, or to prepare to oppose the landings on D-day were also to be frittered away in the defence of the strategically unimportant Italian peninsula. It was to prove a rather futile if glorious campaign for the Allied armies, frustrated by the shortages dictated by the inevitable priorities accorded to preparation for D-day and the Northern Europe Campaign. The Intelligence provided by BP was excellent throughout, but not perhaps of great value in the face of the rather static German defensive fighting in the mountains.

The First Guided Weapons. The first the UK knew about the German development of guided weapons came from the Oslo report in November 1939, but little notice was taken as the British experts believed that ‘the Germans were unlikely to overcome the practical difficulties in perfecting guided weapons’. There were references in the Luftwaffe Enigma decrypts at the end of May 1943 and again in July to the new guided weapons and to the deployment of specially equipped Dornier 217 aircraft to control them. This Intelligence from BP was forwarded to the Mediterranean commands, but no alert was issued to Allied ships. So it caused ‘surprise - indeed profound shock’ when the Hs 293 radio-guided rocket was successfully used against shipping in the Bay of Biscay on 25th & 27th August 1943, sinking the destroyer HMS Egret and damaging others. The sinking of the Italian battleship Roma on 8th September soon followed this, despite warnings from BP issued a few hours earlier that an attack by the specially equipped Dorniers was authorised. BP learnt the next day from Luftwaffe Enigma that the sinking of the Roma was achieved by using the free-fall, radio-guided glider armour-piercing bomb, the FX1400. There were several attacks by the guided weapons on the naval forces off the Salerno beachhead during September, often following warnings from BP, though sometimes the warnings arrived too late to be of use. These attacks severely damaged the cruiser USS Savannah and disabled the cruiser HMS Uganda on 11th September when their guns were much in demand, and nearly sank the battleship HMS Warspite on 16th. Prisoner of War interrogations soon established that there were two quite different weapons, though both were launched from specially equipped Do 217 aircraft. (The subsequent enquiry into why no prior warning had been given before the use of these weapons had commenced, concluded that the problem was that the naval Intelligence staff were not cleared for Ultra and so had to work with bowdlerised information; this resulted in the formation of a Scientific Intelligence Section in the Admiralty who could work closely with Hut 4 at BP). A description of the Hs 293 was soon circulated to ships at sea, and when the airfields round Foggia were captured on 27th September 1943, examination of equipment in abandoned German aircraft disclosed the frequency used by the radio control of both weapons, so radio countermeasures were soon being developed. Thereafter these weapons remained a potent threat, used to attack Plymouth on 29th April 1944, shipping off the beaches after D-day, and the bridges around Avranches after Patton had broken out in early August 1944, but had few successes. In March 1944, Hut 8 at BP and their US opposite numbers broke the cypher of the Japanese Naval Attaché in Berlin and in April one of the first of the many valuable decrypts provided detailed specifications of the weapons, enabling effective jamming.

The Naval Attaché Cyphers. In September 1943 BP broke the Enigma key used by the German naval attaché to Tokyo, Seahorse. For some reason Hut 8 had always thought this naval attaché machine was ‘unsteckered’ - did not have a plug board - but they now found that it used the four-wheel Enigma, like the U-boats. When studied, it proved to use the ‘throw-on’ method of indication with the repeated indicator, like the Porpoise key they had broken in September 1942, and the Sunfish key broken in August 1943. So Seahorse was relatively easy to break but required 4-wheel bombes. Much of the work on Seahorse was taken over by Op-20-G in Washington, once they had modified their bombes to use the repeated indicator, as it was of as much value for Japanese Intelligence as for German. This summer a small part of the Japanese naval code-breaking team in Hut 7 at BP under Hugh Foss, that part which had been working to break the Japanese naval attaché machine known to the Allies as Coral, had moved into Hut 8, so that the skills, tools and approaches adopted in breaking Enigma could be applied to this machine. The British Y station at Sarafand in Palestine had been told to concentrate on intercepts of the JNA 20 code used by the Japanese naval attachés on this machine. Hugh Foss together with Oliver Strachey had broken the earlier naval attaché machine, known as Orange, in November 1934, though the Japanese subsequently introduced complications which hampered the limited effort the British could apply to this key, and was then replaced by the Coral machine which had thwarted both the US codebreakers and the British. The machine, much like other Japanese cypher machines, had two teletypes for input and output and between them three banks of uniselectors that could each move to any one of 26 positions. These uniselector banks can be thought of as the equivalent of the Enigma’s code-wheels, and could be arranged in six different orders, though luckily they only used three of them. A somewhat similar machine, the Jade was in use by the Japanese navy and a team of US code-breakers solved this in August 1943. They turned their attention to Coral, and asked BP to step up their effort on it. Hugh Alexander and other Hut 8 codebreakers now applied their experience of breaking Enigma to Coral, including the Yoxallismus technique for finding the stecker-board connections, devised, of course, by Leslie Yoxall. They made considerable progress and at the end of September 1943 Hugh sent a progress report to OP-20-G that the official US history records as ‘marking the birth of the successful attack on Coral’. In the next few months both Hugh Foss and then Hugh Alexander flew to Washington to help with this work and ‘contributed heavily’ to it. The complete wiring of the machine was finally elucidated on 11th March 1944, the breaking being officially recorded as a joint US-British success. These naval attaché messages between Berlin and Tokyo proved particularly valuable for the detailed technical details about new weapons and the defences of the Atlantic wall. Now BP was able to transfer the team who had been working on Italian naval cyphers to work on Japanese cyphers, many of them, including a number of Wrens, going off to the intensive Japanese courses at Bedford.

Can you help?

'We would like to hear from anyone who worked on Japanese codes who can tell us about the Coral machine used by the Japanese military attaches. Once it was recognised that the architecture was very like Enigma, perhaps the difficulty for the codebreakers (in Hut 8?) was that the messages already coded before being encyphered on the machine?'.

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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