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Seventy Years Ago This Month at Bletchley Park December 1940The First Victories on Land. Throughout the month the bombing of the UK – and Germany – continues in ever more ferocious and indiscriminate fashion. Gradually the British air defence improves, not least because the RAF is learning to take proper advantage of the information gained by the reading of the Luftwaffe signals. The “battle of the navigation beams” is being won, which may not reduce the tonnage of bombs falling on the UK but does reduce its accuracy and so its impact on the war effort. And at last there is good news from overseas; the Greeks have counter-attacked and thrown the Italians back into Albania. And now on the 9th December the British army counter-attacks along the Egyptian coastal strip and throws a much larger Italian army back into Libya. Though of course very few people know it at the time, the reading of the enemy’s signals plays a considerable part in this first significant land victory. Intelligence in the Middle East 1): Italian Army & Air Force. Before Italy entered the war, BP had been regularly reading a wide range of Italian high-grade cyphers, including those of their three armed services, and of their diplomatic service. Decrypts gave nearly a month’s warning about the entry of Italy into the war on 11th June 1940. The Italians changed their army and air force high-grade ciphers on 10th June. They also introduced new lower-grade cyphers for all the Italian armed forces but these were soon read, albeit at first with some delay. By July BP was making progress in reading the new high-grade army and air force cyphers, and by August a steady stream of decrypts was reaching Cairo. BP increased the number of cryptanalysts in Cairo to ensure that as much of the traffic as possible would be read locally. So the British had been expecting the Italian attack from Libya into Egypt on 13th September 1940, though the decrypts did not give the actual date. The arrival of Italian air reinforcements in Albania had been revealed by decrypts and so their attack on Greece on 28th October was no surprise; steps had been taken to provide some limited RAF assistance to Greece and to plan for troop transfers to Crete. In November the cryptanalytical personnel of the separate Service intelligence staffs in Egypt were merged into a single “Combined Bureau Middle East”. BP remained responsible for research and initial attack on high-grade cyphers, while the Bureau took on all work on the M.E. lesser cyphers and for exploiting readable high-grade intercepts. Italy had introduced new high-grade cyphers for the area on 20th September but BP and CBME had begun to recover the army and air force cyphers by the end of that month. The work at BP on the sub-Enigma Army cyphers is being carried out in the Army Section under the remarkable Lt Colonel John Tiltman, one of the greatest of the great BP cryptographers, working in the Mansion and in Hut 5. Air Section, under the highly experienced and capable Josh Cooper, is working on the sub-Enigma Air Force cyphers in the Mansion. Leading their Sections throughout the war, both John Tiltman and Josh Cooper were amongst the nicest of men. Intelligence in the Middle East 2): Italian Navy. The Italian naval high-grade book cypher was changed in July, and was never broken thereafter except by captures. Dilly Knox at BP had first broken the Italian naval Enigma in April 1937, and then he and his girls in the Cottage broke it again in September 1940 but the Italian navy used it for only a few messages a day, though these decrypts were to prove invaluable in the early months of 1941in the run-up to the Battle of Cape Matapan. The Italian navy Enigma machine was taken out of service in the summer of 1941 (no-doubt under pressure from the Germans who recognised how vulnerable a normal Enigma machine without a stecker-board was) and replaced it with the Swedish Hagelin C38m machine, which was soon broken by BP and read regularly thereafter. But at this time in December1940 there was little decrypt information available on the Italian navy, and not much photo-recce information despite the great success at Taranto on 11th November when, aided by a last minute change of plan due to recent photo-recce information, torpedo bombers from HMS Illustrious sank an Italian battleship and two cruisers at their moorings, and damaged two others. British Offensive in the Desert. So in planning his counter-offensive along the Egyptian coastal strip the overall commander in the Middle East, General Archibald Wavell, has the benefit of copious information on the Italian forces that he faces, though less than he would like to have on the Italian navy. In particular about 80 % of the Italian air force high-grade cypher is currently readable until it is changed at the end of December, though it was being read again by the third week in January 1941. And much information is obtained from the Italian army cyphers until they are changed yet again early in January. General Wavell was that rare example of a British general who seemed to grasp immediately how to take advantage of the decrypt information without a long period of building up confidence in the unusually reliable information. Robert Lewin suggests that “Lacking the inhibitions of more conservative officers, Wavell looked at Ultra in a natural way as merely a normal weapon”. Operation Compass, launched on 9th December, achieves complete tactical surprise and is overwhelmingly successful. (It is the first occasion in which the impact of the deception measures being taken by the British to mislead the enemy about the coming attack could be monitored from the enemy’s own signals). By 17th December General Richard O’Connor has thrown the Italians out of Egypt and the battle continues as the Italians retreat along the Libyan coastal strip, which would soon become all too familiar to the armies not just of Italy and Britain but also of Germany. The advance is aided by the steady stream of information on the enemy forces derived from decrypts, in particular from the Italian Air Force. So the British know that the Italians are suffering from the low serviceability of their aircraft. (And the reading of the Luftwaffe Red Enigma Key by BP helps to discount the fear that Germany might be about to come to her ally’s immediate aid). In October the British Army’s cryptanalitical section in Cairo had broken a new group of lower grade codes and cyphers used by the Italian Army. This provides some 8,000 decrypts during Operation Compass. BP succeeds in reading some of the high-grade Army cypher until it is changed in January, sending some 2,600 messages to the War Office for onward transmission to Cairo. And a British field army Y section (3 Mobile Section) provides a stream of traffic from the Italian tactical codes and cyphers, producing over 300 valuable decrypts during December alone. The campaign has been called (probably by Nigel de Grey at BP): “a perfect, if rather miniature, example of the cryptographers’ war”. BP Breaks the Main Abwehr Hand-code. BP had first broken a medium grade German Military Secret Service (Abwehr) cypher in March 1940 when, with the help of a double agent, they read the signals coming from a German spy- trawler off the coast of Norway, though the warning that gave of the forthcoming invasion of Norway failed to be recognised by Naval Intelligence. Now in December 1940 BP breaks the important cypher of the main Abwehr group and continued to read the Abwehr traffic until the Germans adopted a special version of the Enigma machine to carry that traffic. This work on the Abwehr hand cyphers was probably carried out by Oliver Strachey, at that time working in Hut 8, assisted by Henry Dryden. Oliver Strachey was a brother of Lytton Strachey and an old hand from Room 40 in the Admiralty in the First World War. Henry Dryden had joined early in 1939, and had been on detachment to the small team of cryptographers with the British Army Intelligence team in France. In mid 1941, when the Abwehr started to use a machine, the work at BP on their cyphers was split into two teams, with Oliver Strachey and his team (ISOS) continuing to work on the hand cyphers, and Dilly Knox and his team (ISK) taking on the machine. (IS stood for Intelligence Section though it seems to have been widely understood at BP to stand for “Illicit Services”). Dilly and Peter Twinn finally unravelled the Abwehr Enigma in the autumn of 1941, working in Cottage 3. Being able to read the enemy’s Secret Service cyphers enables M.I.5 to trace, then to eliminate the German spies in the UK, and then M.I.6 to monitor the extent to which the Germans are swallowing our hugely important deception programmes. Under the double-cross programme, turned German spies feed doctored ‘information’ to Germany. Liaison with the USA. Discussions between the UK and the USA on defence matters went back until at least 1937, but had rarely extended to intelligence matters. Then in May 1940 the UK Secret Intelligence Service appointed Colonel Stephenson to be their liaison officer with the American Intelligence Services. No doubt with the encouragement of Churchill, Stephenson was able to establish excellent relations with President Roosevelt. This resulted in the President’s special envoy, Colonel Donovan, visiting the UK in July 1940. One of his objectives on behalf of the US Navy Department was to see if a closer collaboration on Intelligence matters could be arranged. The British government invited a United States delegation to come to London for talks about “Standardisation of Arms”, and at those talks a US Army representative on the delegation outlined the progress his service was making against Japanese and Italian cyphers and formally proposed that the time had come for a free exchange of Intelligence information. Colonel Donovan returned to Washington to recommend a full exchange of Intelligence between the two Naval Intelligence departments. On 7th September the President agreed that the US Intelligence Services might make available to the British any relevant information from US diplomatic and consular services, and assured Col Stevenson that the UK would be given every assistance in obtaining information on any topic it might raise. Roosevelt agreed that the two countries would exchange complete technical information about Japanese, German, and Italian codes and cyphers – but excluding an exchange of actual intercepts. Senior US and British representatives in Washington formally agreed this accord in December 1940. All this was going on at a time when there was strong resistance to getting involved in the USA. Co-operation with USA on Japanese Codes? Probably BP did not expect that the US had much to exchange. Certainly the Intelligence Services were coming to believe that their opposite numbers in the US could not help much with matters in the European theatre. But perhaps they could for Pacific Ocean matters? In the UK in November 1934, Hugh Foss and Oliver Strachey of GC&CS had made the first break into the Japanese Type A diplomatic cypher machine, and had designed an “emulator” (the “J machine” built by the Metropolitan Police wireless staff at Denmark Hill working for GC&CS) to assist with the decipherment of the signals. And Captain John Tiltman had broken the signals of the Japanese military attaché in 1933, and new military cyphers in 1938 (while working at Bletchley Park during the temporary move of GC&CS there during the Munich crisis). But with the coming of the war the effort at BP had had to be largely diverted to the struggle to read German Enigma, and it was the US Army team, led by the great cryptographer William Friedman, who made the first break into the new Japanese diplomatic cypher machine, Type B known to the US as Purple, on 27th September 1940. So when Roosevelt first agreed to the exchange of intelligence information this break had not been made, but it had by the time the accord was signed. Had Churchill told Roosevelt in confidence about the BP break into Enigma? It seems very probable that Roosevelt was aware of the British success, in outline. So the first steps were taken to that great accord between the two nations in Intelligence matters that grew into the “BRUSA” agreement that lasts until this day. The path of true love certainly did not always run smooth, then or now, but taken overall it was to prove of the utmost significance - for both countries. BP at the end of 1940. When BP first moved back into the Park in August 1939 there were some 137 staff, and a further 49 in the Construction section, which soon moved on to Mansfield College, Oxford, though remaining under the control of the BP top-management. By now in December 1940, there are some 550 staff at the Park (excluding the Construction Section, and the guards, cleaners, etc) with a further 100 in the Y stations at Denmark Hill (the pre-war home of the Metropolitan Police radio intercept unit in South London), Sandridge (the pre-war home of the Post Office radio intercept station near St Albans), Wavendon (a mansion a few miles from BP which serves as the shadow site in case BP is bombed, and is now housing one of the two precious Turing bombes), and Broadway (the London home of GC&CS, now largely empty but to be reoccupied in a year’s time by the Diplomatic & Commercial codebreakers from BP). The BP staff is working in the Mansion (124), the first eight Huts (291), the Cottage (10: Dilly Knox and his 9 female team), and the School House (67). At this time the Wrens have not yet arrived, but there are 7 WAAF working in the teleprinter and telephone exchange room (the “Teleprincesses”) in the Mansion (Room 5, the Ballroom), and 35 WAAF in the “Communications Section”. There are 12 “Volunteer, ATS” in the Military section, Hut 5. Of the 550 staff at the Park, 322 are female, with a further 31 amongst the 56 staff at Wavendon. The Director, Alastair Denniston, in dealing with a minor outburst about the living conditions staged by Oliver Strachey and others in Hut 8 writes “So far as I am aware the attitude of all the staff is keener than it has ever been. All know that they are assisting to the best of their ability in an effort that is bearing fruit on nearly every branch”. True, but over-worked and ill led? The Bletchley Park Trust welcomes the preparation of these notes, but the authors are responsible for the statements and the views expressed. |
