Seventy Years Ago This Month at Bletchley Park

October 1939

Germany completes invasion of Poland.  Although the starving people of Warsaw had surrendered on 27th September, the Germans delay their triumphal entry until 1st October.  The impact of aerial bombardment had been devastating.  The final battle in Poland takes place near Kock, seventy miles south-east of Warsaw from 2nd to 5th October when General Kleeberg’s group, after complete encirclement, finally surrenders when they run out of ammunition.  Hitler takes the salute in Warsaw on the 5th October.  In total during the one-month campaign some 60,000 Polish soldiers have been killed, with 25,000 civilian casualties.  The Germans capture 694,000 Polish troops, with a further 217,000 taken by the Russians. Many of these captives are to die in slave-labour camps. The German losses amounted to not more than 14,000 men. Now the murder of the Polish upper classes is being implemented; thousands of teachers, doctors, priests and other professional people are rounded up and slaughtered. The aim is stated explicitly as being to eliminate the governing classes.  The surviving Jews are constrained to a few cities; the medieval ghettos reappear. At least one honourable German, Field-Marshal von Rundstedt, orders that such activities should cease in the areas under his control.  And the escape to the West continues, with some 40,000 military and civilian Poles eventually reaching France, where General Sikorski has established his Government-in-Exile on 30th September.  Some Polish destroyers and submarines succeed in evading the German blockade and make their way to Britain.

Germany and Russia dismantle the old Poland.  Poland is partitioned between the Germans and the Russians whose armies cover up to 350 kilometres in a week as they move up to the secretly agreed demarcation line along the Rivers Bug and San.  Stalin agrees to supply Germany with oil in return for the eastern provinces of Poland, which he incorporates into the Soviet Ukraine. Germany incorporates the western provinces into its fast growing Empire.  Poland is partitioned and eliminated from the map of Europe except for an area around Warsaw, which is to be treated “like a German colony”.  With Hitler’s acquiescence, Stalin moves to take control of the three Baltic States, Estonia, Latvia and Lithuania giving Russian access to the naval bases on the Baltic.

The Phoney War.  Meanwhile in October, and for months to come, activity on the Western front and along the Maginot line is confined to patrolling; except at sea, action by Britain and France is reduced to propaganda. The Prime Minister, Neville Chamberlain, explains “there is no hurry as time is on our side”. And in any case “it might well be that the morale of Germany will crumble”. British bombers continue to fly over Germany, on the night of 1st October over Berlin, – dropping leaflets! But early in October this “confetti war” is discontinued because the British public find that this pathetic campaign makes even worse the humiliation they feel over failing to come to the aid of their Polish allies. 

However, unknown to the British public, at least the secret “double-cross” war had started with a success when the Welshmen, Arthur Owens and Gwilym Williams convince the Germans that they are good fascist agents.  This leads to a deception campaign in Wales with a sham sabotage plan aimed at the water reservoirs.  It triggers the unveiling of one of the few remaining German agents in the country, who soon finds himself recruited into the burgeoning British double-cross campaign. [It was to be the reading by BP of the codes of the German Counter-Intelligence Service, the Abwehr, which made the double-cross campaign so successful, for BP helped the British controllers to know just what the Germans were trying to do with their agents].

Hitler prepares an offensive against the West.  In a public speech on 6th October Hitler suggests that peace might be possible, and secret negotiations with Britain take place.  But on the 14th October a British battleship, HMS Royal Oak, is sunk by a German submarine at its anchorage in Scapa Flow, joining the aircraft carrier Courageous that had been sunk in the Western Approaches. More British naval ships are sunk in air raids on Rosyth and Scapa Flow in mid-October.  These disasters make it difficult to take the negotiations seriously.  And indeed on 9th October in secret, Hitler has issued a directive to his commanders to prepare for an offensive through Holland, Belgium, Luxembourg and Northern France to take place on 12th November.  That date is known to the British Cabinet, due to a leak from officers working for Admiral Canaris who controls the Abwehr. The British Intelligence survey at the outbreak of war had predicted that Germany would over-run Poland in three weeks and would then launch an offensive in the West during November. That the attack was imminent was confirmed by warnings from the Dutch Military Attaché in Berlin, via the Vatican. [This offensive was postponed, at first due to bad weather].

The Polish code-breakers resume work with the French.  Having escaped from Poland via Bucharest, the three great Polish code-breakers arrive in Paris where they are welcomed by the French “Fifth Bureau”, the intelligence staff of the Army General Staff.  On 20th October the “Radio Intelligence” service of the Bureau is established in the large Château de Vignolles at Gretz-Armainvilliers, about thirty-kilometres south-east of Paris – code name P.C. Bruno.  Close collaboration has been established with the British team at Bletchley Park and an on-going exchange of information is initiated.  Some of the French listening posts can receive German signals that the British Y service cannot cover.

At Bletchley Park work is in progress that will lead to the breaking of Enigma keys.  Work is now well established at Bletchley Park on the various hand cyphers and minor codes that are being broken there at this time.  But in Cottage 3 in the Stable Yard the Research Section, under the loose leadership of Arthur Dillwyn (Dilly) Knox, is working on the two methods that will lead to the break into Enigma.  Dilly Knox had carried out some distinguished work in Room 40 in the Admiralty during the First World War, and had continued to work for GC&CS between the wars, interspersed with translating some of the minor Greek poets.  He was a great character and a most distinguished code-breaker who would triumph over both an Italian naval cypher and an Abwehr system before, sadly, he died from cancer in February 1943. But he was no great communicator, and was far from easy to work with by now.  Gordon Welchman describes him as “neither an organisation man nor a technical man.  He was, essentially an idea-struck man… By and large, Dilly seems to have disliked most of the men with whom he came into contact”.  He had been at the famous meeting in Poland in July 1939 when the Poles had told the British and the French about their great work on Enigma. The Poles and Dilly seem to have developed a mutual respect. But he probably told only a few of his immediate colleagues what he had learnt there; perhaps just Peter Twinn, John Jeffreys and Alan Turing – certainly not Gordon Welchman who, like Jeffreys and Turing, had joined the BP Research team from Cambridge when war broke out.

Alan Turing, fresh from Kings College, Cambridge, is working on the design of his “bombe” machine, and discussions about manufacture are in progress with “Doc” Keen of the British Tabulating Machine Co.  And John Jeffreys, fresh from Downing College, Cambridge is working on the “Netz” sheet method, though it now requires ten times as many sheets as the Poles had been employing. The Germans had increased the number of different code-wheels for the three slots in the Enigma machine from three to five, so increasing the possible wheel order permutations from 6 to 60.  Jeffreys is developing a machine to mark where the holes have to be punched in the sheets.  60 sets of 26 sheets each are required.  [Punching the holes starts in November and finally the two-millionth hole is completed in December]. Originally the method had been devised by the Polish code-breaker, Henryk Zygalski [who stayed on in Britain after the war as a lecturer at Battersea Tech].  Dilly Knox had earlier devised, but not implemented, a form of this method using linear film rather than sheets, and the method was reinvented by Gordon Welchman in September; he told Dilly only to learn then that the sheets were already in preparation.  [When completed these sheets provide the first wartime break into Enigma in January 1940; sadly, John Jeffreys has to leave BP a few weeks later through ill health, and dies before the end of the war].

Preparations to scale up the Effort.  Gordon Welchman convinces the Deputy Director, Edward Travis, that a large scaling up of the effort will be needed when these methods work. Then, remarkably, Travis persuades Whitehall to provide the resources to back this gamble. Gordon is 33 years old when he comes to BP in September, and had been a Fellow of Sidney Sussex College, Cambridge for the past ten years. Like Alan Turing he is a mathematician, but is working on geometric mathematics, while Alan’s interests are in logical mathematics.  But they had certainly met before they came down to the Park together on 4th September, if only at the few week-end courses on codebreaking that GC&CS had run during 1938/9 for its reserve of academic recruits. Like Alan, Gordon had been allocated to the Research Section, but the Cottage was so crowded that Dilly Knox sent him off to the near-by requisitioned Elmers School. He was supposed to be carrying out ‘traffic analyses’ – looking at the intercepted signals to try to determine where they came from and so provide some indication of military movements, etc. Gordon clearly felt that Dilly did not like him, and so had quarantined him away from the priority work on Enigma in the Cottage. But, in fact in a note to the Director, undated and written on his home note-paper probably early in October, Dilly records that Gordon Welchman is ‘doing well & is keen. I hope soon to get him back here to learn up about the machines’. He might have been less enthusiastic if he had known that Gordon had spoken the Deputy Director, Edward Travis about the need to scale up the effort, once an Enigma key is broken. He is proposing a form of ‘Taylorism’, or mass production, with the cryptographic task broken into parts, each handled by its own specialists. He produces a drawing of what such a hut might look like, with space for Sorting & Receiving the flow of incoming intercepts from the Y stations, with room set aside for 6 Netz stacking tables, for three ‘Bombes’, and for eight people who he calls  ‘decoders’, each working at an Enigma machine. The flow ends with space for RAF and War Office experts, presumably Intelligence Officers to translate and to prepare the outgoing messages.  [It was in essence, a remarkable piece of forward thinking in which he envisaged what was in a few months to become Hut 6 – under his leadership]. No doubt he was well aware that Dilly would strongly dispute such a division of the work into sub-tasks, each undertaken by a specialist in just that sub-task, for Dilly held the view that one code-breaker must take responsibility for all the stages of work on a particular intercept (as a Greek scholar, like himself, would do on ‘decoding’ an ancient papyrus, for example). Gordon realised that the flood of intercepts from a break into Enigma would make such an approach an unrealistic luxury. 

The Y Stations.  The old hands in GC&CS had been concerned that the outbreak of war would lead to a marked fall off in the radio traffic that could be intercepted, as radio silence would be imposed. Just this had happened at sea in the last year of World War I, when tightened security had silenced much of the German fleet’s radio signals. The same had happened on the Western Front once the war had developed a static quality and land-lines had been increasingly employed. But on land there had been an upsurge of radio traffic in the last year of the war, as the fronts became more fluid, as a result of the last big, more mobile offensives by both sides. And now, experience from the invasion of Poland in the early days of WWII suggested that radio traffic would rise once an offensive had begun, even if radio silence reduced the traffic prior to a new offensive. [To the relief of GC&CS, this became the pattern on both sides, with an ever increasing amount of radio communications being used throughout the war, interspersed with a few periods when the traffic fell temporarily as land-lines were reintroduced in periods of static warfare].   In the early days of WWII, the main interception station (called a Y station) for Army and, in practice Air Force, traffic was based at Chatham above the old naval base, manned by the Royal Signals. The Navy had two Y stations at the outbreak of the war, HMS Flowerdown, near Winchester, and one on the cliffs at Scarborough. And there was one main RAF interception station at Cheadle.  [As the war progressed the number of Y stations steadily increased until by the end there were about 36 in the UK, and numerous others overseas, close behind every battle front].  The material from the Y stations was intended to be sent by teleprinter to BP, but despite the large number of telephone lines that were laid into the Park from the main north-south telephone cable that passed nearby alongside the A5 major road, there was always a shortage of teleprinters or teleprinter operators (affectionately called the ‘teleprincesses’ at BP) so much of the intercepts were batched up and sent by dispatch rider to BP. [After the early months it was agreed that communications at BP would be manned by the WAAF, of whom there were some 1,400 in the communications centre in Block E at the end of the war].

The Bletchley Park Trust welcomes the preparation of these notes, but the authors are responsible for
the statements and the views expressed.