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December 1943 : The Approach to Monte Cassino

In his plan for the assault on the Gustav Line, General Alexander envisaged converging attacks round Monte Cassino, the Fifth Army from the south and the Eighth Army from the northwest having advanced along the coast north of Pescara before turning southwest towards Avezzano and Rome. At the beginning of December on the Eighth Army front the crossing of the Sangro in flood proves very expensive, and in the street fighting in Ortona, just short of Pescara, the Canadian 1st Division suffers over 1,370 casualties before the month is out. Now some of the best of that Army has left to be transferred to England to prepare for the Normandy landings. General Montgomery himself leaves on 30th December, visiting Churchill who is recovering from pneumonia in Marrakech, but not before recommending to General Alexander that the Eighth Army offensive should be halted. He takes much of his staff with him to form the basis of the staff of 21st Army Group in England, and is replaced by Lieut-Gen. Sir Oliver Leese. There are plans for a limited amphibious assault at Anzio, just south of Rome, to be launched once the US 1st Armoured Division has reached Frosinone behind the Gustav line. It had originally been intended that most of the landing ships in the Mediterranean should be transferred to Britain but it is finally agreed that enough to land one division should be retained until mid-January. So Mark Clark starts his offensive on 2nd December before his army is fully prepared, in the hope of getting far enough north before this dead-line to launch the proposed landing. Monte Camino is taken after fierce fighting, changing hands on several occasions. The French 2nd Moroccan Division prove excellent fighters in the mountainous terrain, and, to the north of Monte Cassino, force the Germans back to the Gustav line. But this success is unexpected and no reserve is provided to follow through. The troops are exhausted, the further advance of both armies is thwarted, and the landing has to be postponed. It is not a happy Christmas for the troops in the bitter weather of the mountains of central Italy, and especially those now facing the formidable Monte Cassino. Excellent Intelligence, which provides a wealth of detail about the enemy’s order of battle, the state of his divisions, his supply situation and the development of his defence positions, is proving of little avail when the Germans are in strong defensive positions in mountainous country where advantage can rarely be made of the Allied superiority in armour and in the air. The good Intelligence enables such a successful attack on Italian rail communications that Kesselring deduces that the Allies are being advised by the Italian transport authorities; wrong but better than deducing that the information comes from decrypts of his staff’s signals! The decrypt of three lengthy reports from Kesselring during December gives details of the state of development of prepared positions along the whole front. By the end of December the Joint Intelligence Committee concludes that the Germans have never yet been thrown so far off balance in Italy as to oblige them to make a change of plan; Kesselring still intends to deny Rome to the Allies for as long as possible. Even the objective of locking up German forces in Italy is known to be only partly succeeding as he has transferred some divisions away from Italy to cope with the threat from the new Russian winter offensive. The Italian campaign has become an expensive sideshow, as the troops there are all too well aware.

The Sinking of the Scharnhorst. In March 1943 the Artic convoys, carrying much needed supplies to Russia, had had to be suspended because of the losses caused by U-boats and the threat from the German surface ships in Altenfiord, notably the Tirpitz and the Scharnhorst. At the time the priority of protecting the Atlantic convoys meant that Britain lacked the capital ships to adequately defend the convoys. On 22nd September midget submarines, the X-craft, succeeded in seriously damaging the Tirpitz. Now it is decided to renew the Artic convoys, and decrypts convince Admiral Sir Bruce Fraser that the Scharnhorst will risk coming out to attack the December convoys. In fact there had been dissention in the senior German naval ranks about the desirability of risking her, but Admiral Dönitz has ordered her to sea because it is considered so important to try to disrupt the supplies at a time when the Russian winter offensive is in full flood. At 1900 hrs on Christmas Day Scharnhorst sails with an escort of five destroyers. A new Enigma Dolphin key setting had come into force at mid-day, so it is not until 0025 hrs on 26th December that the German executive order ‘Ostfront 1700/25/12’ is decrypted. The Admiralty Operational Intelligence Centre issues this information to the Fleet, together with the comment that the meaning of the code-word is not yet evident. But by 0217 hrs they are able to issue the emergency Ultra signal ‘Scharnhorst probably sailed 1800 hrs on 25th December’, soon following this up with the general message ‘Admiralty appreciates Scharnhorst at sea’. BP then decodes a series of Enigma Dolphin Offizier signals, but are unable to read 12 messages that they deduced are in the surface ships key Barracuda, which is not being read at this time. The decrypts keep Admiral Fraser fully informed both about the enemy’s intentions and about their current state of knowledge about the British forces. Armed with this excellent Intelligence, Fraser takes the risk of breaking radio-silence to order the convoy to alter course to give his force time to close. Luftwaffe reconnaissance aircraft soon spot his flagship, the modern battleship Duke of York, with its escort, and thereafter shadow this group. But the German naval authorities seem to have chosen to ignore the warnings from these aircraft, though it is not certain what the undecrypted Barracuda messages read. Enigma decrypts tell Admiral Fraser that the Luftwaffe has not spotted the other strong cruiser task force that is protecting the convoy, though U-boats have found the convoy. By radar this convoy covering force picks up the Scharnhorst, which is closing from the south in heavy seas, and the cruiser Norfolk opens fire by 0929 hrs on the 26th. The Scharnhorst is slightly hit, and immediately breaks off the attack, sailing away at speed to the northeast. Correctly deducing that she will make a second attempt on the convoy from the north, the covering force locates her again shortly after 1200 hrs. At a range of 11,000 yards, in terrible seas, the covering force opens fire. Scharnhorst responds with her 11-inch guns and soon has the Norfolk largely disabled, but once again Scharnhorst disengages and turns south to run for home. The covering force is able to shadow her as the Duke of York closes from the west at her full 24 knots despite the heavy seas. At 1617 hrs she picks up Scharnhorst on her radar. The two ships aim salvo after salvo at each other, but, partly due to the superiority of the British gunnery radar, it is thought the Duke of York lands as many as thirteen of her 14-inch shells on the Scharnhorst, while herself suffering hardly any damage. At 1830 hrs the guns of the brave Scharnhorst fall silent and torpedoes finally finish her off. Despite efforts, only 36 of her crew of 2,000 are picked up from the icy waters.

Progress on Robinson & Colossus. When Heath Robinson had proved that it could be used to find the settings of one bank of the code wheels, 12 more improved models of the machine were ordered and the first of these arrived at BP in November 1943, soon followed by three more at roughly monthly intervals. [Due to the success of Colossus the rest were cancelled, though variants were developed, such as Old Robinson fitted with a printer, and Super Rob enabling ‘spanning’]. The Newmanry is now eagerly awaiting their new machine, Colossus. It has been operated successfully at Dollis Hill on test tapes, but its transfer to BP is delayed while a typewriter output is added, as it has proved difficult to record the counts correctly by reading the electronic valve counter totals on a projected light bulb screen on Robinson. Shortly before Colossus was finished, Gifford at TRE suggested he could design a device to print out these counts and the related wheel positions. This recording proved ‘an indispensable part of the process’, but the building of the printer rack caused some weeks delay in the delivery of Colossus to BP, even though the work is said to have continued throughout Christmas. [The Gifford printer had the advantage over the standard IBM electromagnetic printer of the day in that it could record eight digits at once; however it proved very unreliable and in due course was replaced by a modified IBM electromatic typewriter. Max Newman records, in a minute to the Director on the 18th January 1944 ‘Colossus arrives today’]. Meanwhile work in the Newmanry continues to bring the new Robinsons into service. Because of errors in punching tapes experienced in the Newmanry in the early days of trying to make Heath-Robinson work, all tapes prepared for the counting machines were punched twice independently and compared before use. At this time the prototypes of two tape handling machines for use with the Robinsons and Colossus, called Miles and Garbo, were introduced at BP. Miles, at first called Mrs Miles after a lady who gave birth to quadruplets, made up to four tape outputs by combining up to five tape inputs for crib runs and largely employed electronics rather than mechanical relays. Garbo was a machine for printing from a tape involving operations like differencing; inevitably, its output was called Garbage.

BP at the end of 1943: 1) Staff Numbers. The year 1943 has seen an enormous growth in numbers at BP. The official returns for the BP part of GC&CS (that excludes the ‘Commercial & Diplomatic’ sections under Cmdr Alastair Denniston who have been back in London since February 1942) show that the numbers have grown from 3,100 at the beginning of the year to more than double at 6,800 at the end of 1943. The growth will continue until the end of the war in Europe, but the rate of increase is now beginning to slow. Of the 6,800, some 1,400 are Wrens working at five bombe outstations off-site, Adstock, Gayhurst, Wavendon, Stanmore, and Eastcote. There are now a further 500 Wrens on site at BP, working largely in Hut 8, Naval Section, and the Newmanry. Of the 6,800 total, 3,800 are in the Services, of whom 2,900 are women; 670 of these are WAAF, largely in the Communications centre of Block E; and 330 are in the ATS, largely in Hut 6 and the Military Section, both now in Block D. Of the 3,000 civilians, some 2,400 are women, formally working for the Foreign Office. So 5,300 of the 6,800 total are women, most of them girls only just out of school.

2) Enigma. There are 400 staff working in Hut 6 on the Army & Luftwaffe Enigma codebreaking; and 126 in Hut 8 working on the Naval Enigma codebreaking, but now they are complemented by the OP20-G team in Washington rapidly growing to be larger than the BP team on Naval Enigma. There are 370 working on the Army & Luftwaffe Intelligence in Hut 3, as translators, Intelligence extractors, and creating the now huge ‘index’ of background information covering all aspects of German military affairs. Most of the Enigma teams are now located in Block D, and of course they are beginning to prepare for the flood of work that is expected to emerge as soon as the Allied armies land back in Northern Europe. There are now 99 bombes available in the UK, and a further 77 American bombes in Washington. At last BP has enough bombe time to use them lavishly to break new keys, and to avoid using the manpower intensive methods designed to reduce bombe time, like Banburismus. They have broken so many German Enigma keys that not all can be read every day so a system has been introduced of concentrating on the 30 to 50 keys each day that seem most important at that time. Now they are regularly breaking, on average, some 1,600 Luftwaffe and Army Enigma signals each day, some 1,200 Naval Enigma signals, and other Enigma signals such as those of the Abwehr and railways are being broken in other sections.

3) Fish. The Newmanry, working on machine methods of breaking the top-level Fish codes and which was formed only at the beginning of the year, is now expanding fast and has reached 65 staff. The Newmanry has now established that it can provide some of the Fish machine (the Lorenz SZ42A) wheels settings once the Testery has worked out the wheel teeth positions which, at this time, still only change every month. The Testery is formally part of the Military Section and probably accounts for at least 100 of the 390 staff now in that section. They have broken several of the links from the German Army central staff in Berlin, in particular those to Italy and to several of the Army groups on the Eastern front. This month the Germans introduce a modification to their machines that eliminates depths, so removing the ability of the Testery to do some of the wheel setting by hand methods, making it essential to use the Newmanry machine methods. In total the number of Fish messages broken each month has declined somewhat as the Germans have tightened up on their methods of indicating the wheel settings and are changing some of the wheel settings more frequently, but together the Testery and Newmanry are still, for the moment, breaking some 250 each month of the long and most important messages.

4) Abwehr Codes. Some of the hand codes of the German military secret service, the Abwehr, were first broken back in 1940, and a team under Dilly Knox carried out the breaking of the Abwehr Enigma codes in the autumn of 1941. (It was the last major contribution of the great veteran code-breaker before he died of cancer in February 1943). Now 89 strong, the ISOS under Oliver Strachey is continuing to break the hand-codes, and ISK, 86 strong, under Peter Twinn is regularly breaking the Abwehr Enigma codes. Because of the unusual turn-over pattern of the wheels of the Enigma machine used by the Abwehr, the ISK team now has two special bombes to help them with this work, known as the ‘Funf’ type; (those who remember their Tommy Handley ‘ITMA’ broadcasts will recognise the origin of the name). Their work is always of value for the insight it gives into the German spying activity. But now it has become invaluable by showing the German concerns about future Allied operations, which provides the basis on which deception campaigns can be built. The seeds are now being sown that will flower in the very successful deceptions before the landings both at Anzio and in Normandy.

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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