May 5, 2013

Finest Hour 151, Summer 2011

Page 44

Churchill and Intelligence – Golden Eggs: The Secret War, 1940-1945 / Part III: Closing the Ring

Again and again, before and during the desert battles and landings in Europe, Enigma decrypts monitored by Churchill gave precious clues that saved Allied lives.

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By Martin Gilbert

The Western Desert

During each phase of the war in the Western Desert, Enigma revealed German strengths and weaknesses, including Rommel’s fuel shortages, and the dates and routes of the despatch of fuel oil by ship across the Mediterranean. The army, navy and air commanders-in-chief were thus notified when and where the enemy was weak, and what advantages could be taken. On 4 May 1941, for example, Churchill drew the attention of General Wavell, Commander-in-Chief Middle East, to a decrypt that had just been sent him, with the note: “Presume you realize authoritative character of this information.”

Churchill, asking Brigadier Menzies, head of the Secret Intelligence Service, for a translation of the actual decrypt rather than the usual summary, added: “Actual text more impressive than paraphrase showing enemy ‘thoroughly exhausted,’ unable, pending arrival 15th Panzer Division and of reinforcements, to do more than hold ground gained at Tobruk…also definitely forbidding any advance beyond Sollum, expert for reconnaissance, without permission.”¹ Enigma would reveal if that permission were given.

Churchill sent General Wavell the unsummarized translated text of an Enigma message decrypted three days earlier. Normally, to protect the source of the information, only summaries or paraphrases were sent, but Churchill judged it crucial for Wavell to know precisely what the Germans were planning. OL (Orange Leonard), the prefix to the message, was a typical digraph used to transmit messages from an individual spy: anyone other than Wavell who saw this reference would assume that it was an agent and would be unaware of the true source.

Wavell’s successors, Generals Auchinleck and Montgomery, were each regular beneficiaries of the daily flow of decrypted German messages. On 6 November 1941, Churchill in one of his first telegrams to Auchinleck wrote: “I presume you are watching the constant arrival of anti-tank guns upon your front, both as observed by road and as reported in our most secret by air.”² The “most secret” were Enigma messages from the Luftwaffe. In the second week of November Churchill informed Roosevelt that two Axis convoys on their way to Benghazi with fuel oil and military supplies for Rommel had been sunk.³ The destruction of the convoy had been possible because of intercepted messages which, when deciphered, had given their precise routes and timings of the convoys.

Churchill was worried lest the secrecy of his Signals Intelligence be endangered. When he asked Menzies about a British naval signal from Malta giving details of the convoy, Menzies reassured him: “The Malta signal was sent out as a result of an aircraft sighting, which quite naturally corresponded with our Most Secret information. The signal, however, was based on the aircraft sighting and not on our material. No security, therefore, was disregarded.”⁴

A day after Auchinleck launched his November offensive in the Western Desert, Enigma revealed a setback to his troops in a sudden flash flood. Churchill ensured that Auchinleck noted this “special information.”⁵ Churchill was even able to follow Auchinleck’s advance through Enigma, telegraphing on November 21st: “From what I learn from special sources which you know, I have formed a favourable impression of your operations.”⁶

On the fifth day of the battle, concerned to maintain the secrecy of the Enigma-based information during the inevitable ebb and flow of troops and armies, Churchill telegraphed: “C is sending you daily our special stuff. Feel sure you will not let any of this go into battle zone except as statements on your own authority with no trace of origin and not too close a coincidence. There seem great dangers of documents being captured in view of battle confusion. Excuse my anxiety.”⁷

Two days later Churchill repeated his concern: “Please burn all special stuff and flimsies while up at the Front.”⁸

Churchill’s scrutiny of Enigma was continuous. Also on November 23rd he informed Auchinleck that he had asked Brigadier Menzies “to emphasise to you the importance of our MK 9.” Churchill hoped this information would encourage Auchinleck to run “quite exceptional risks.”⁹ Drawing Admiral Cunningham’s attention to this same Enigma, Churchill telegraphed:

I asked the First Sea Lord to wireless you today about the vital importance of intercepting surface ships bringing reinforcements, supplies and, above all, fuel to Benghazi. Our information here shows a number of vessels now approaching or starting. Request has been made by enemy for air protection, but this cannot be given owing to absorption in battle of his African air force. All this information has been repeated to you. I shall be glad to hear through Admiralty what action you propose to take. The stopping of these ships may save thousands of lives, apart from aiding a victory of cardinal importance.¹⁰

What Churchill called “our information here” was the summary of a decrypt giving details of the German air fuel cargo on board two oil tankers, Maritza and Procida, destined for Benghazi and the German airfield at nearby Benina.¹¹ Within twenty-four hours of Churchill’s telegram, both ships had been sunk, and Rommel’s aircraft fuel supply drastically curtailed.

Enigma determined the British decision to take the offensive in the Western Desert. On 15 March 1942, Churchill explained to Auchinleck: “A heavy German counter-stroke upon the Russians must be expected soon, and it would be thought intolerable if the 635,000 men on your ration strength should remain unengaged preparing for another set-piece battle in July.”¹² If no earlier offensive was possible in the desert, Churchill added a day later— knowing from Enigma the German strategic plans—it might be necessary to transfer fifteen air squadrons from the Western Desert “to sustain the Russian left wing in the Caucasus.”¹³

One crucial Enigma message on 2 May 1942 revealed that by June 1st, Rommel would have enough fuel for a thirty-eight day tank offensive.¹⁴ Rommel launched his offensive on May 26th. Knowing the date, Churchill had urged Auchinleck to strike first, but Auchinleck had felt unable to do so.

On 20 August 1942, Churchill, then in Egypt, visited the forward positions at Alam Halfa across which, it was already known from Enigma, Rommel’s attack would come. Enigma also indicated that Rommel might launch his attack on 25 August. Churchill immediately appointed General Maitland Wilson to establish a defensive line for Cairo and the Suez Canal. Further Enigma decrypts gave five days’ respite: the attack came on the night of August 30th.

While in Cairo, the Prime Minister was allocated a Special Communications Unit to provide direct access to the Enigma decrypts. His wireless operator was Edgar Harrison, who was later seconded to him on his visits to Turkey, Nicosia, Teheran and Yalta.¹⁵

Enigma decrypts continued to expose Rommel’s fuel supply. When one signal reported the sailing of a convoy from Italy to North Africa on September 6th, Churchill wrote to the naval and air chiefs, Sir Dudley Pound and Sir Charles Portal: “This is evidently an occasion for a supreme effort, even at the risk of great sacrifices by the Navy and Air Force. Pray inform me tonight what action you are taking.”¹⁶ The action was to attack the convoy. Three of its four merchant ships, laden with aviation fuel, were sunk.

A decrypt on 8 October 1942, a message from the Western Desert to the German High Command, revealed Panzer fuel stocks would soon be down to four and a half days’ battle supply, and that only three days’ worth of this fuel was located between Tobruk and Alamein. This message was decrypted at Bletchley at virtually the same moment it was read in Berlin. The decrypt was sent to Menzies, then immediately to Churchill, the chiefs of staff and Montgomery. The decrypt continued that as a result of this fuel shortage, the Panzer army “did not possess the operational freedom of movement which was absolutely essential in consideration of the fact that the British offensive can be expected to start any day.”¹⁷

A series of October decrypts had enabled the RAF to pinpoint and to sink the “vitally needed tankers” bringing tank and aircraft fuel across the Mediterranean to the German and Italian forces in North Africa. Further decrypts revealed “the condition of intense strain and anxiety behind the enemy’s front,” giving the Defence Committee “solid grounds for confidence in your final success.”¹⁸

On the evening of November 2nd, Rommel sent an emergency situation report to the German High Command: His forces were exhausted, and no longer able “to prevent a further attempt by strong enemy tank formations to break through, which may be expected tonight or tomorrow.” On the other hand, Rommel told Berlin, an “ordered” withdrawal of his troops was impossible in view of the lack of motor vehicles. Rommel added: “The slight stocks of fuel do not allow for a movement to the rear over great distances.” On the “one available road” his troops would certainly be attacked “night and day” by the RAF. In this situation, he warned, “the gradual annihilation of the army must be faced.”

The decrypt of this message reached Churchill on the night of November 2nd, when a copy was also sent to Cairo for Alexander. Three other decrypts that same day testified to the imminence of a German retreat, and the exhaustion of the German army. “Presume you have read all the Boniface,” Churchill telegraphed to Alexander on November 4th.¹⁹

Following the Allied victory at El Alamein, Montgomery advanced westward. After landings in Morocco and Algeria, the Americans under Eisenhower advanced eastward. Tunisia became the battleground of both forces against a determined enemy. Enigma decrypts over a ten-day period showed Churchill and the Combined Chiefs of Staff the extent to which Hitler was determined to hold Tunisia, and alerted them to strong Axis reinforcements, including several formations of high quality: 10,000 German and Italian troops in the second week of November, with 15,000 more to follow.²⁰ When military setbacks took place—disturbing Allied public opinion—the detailed reasons for them could not be explained publicly, for fear of disclosing the source of the knowledge.

A month later, Enigma decrypts showed the effect of Allied air and sea attacks. “Boniface shows the hard straits of the enemy,” Churchill telegraphed Eisenhower on December 16th, “the toll taken of his supplies by sub-marines and surface ships, and especially the effect which our bombing is having upon congested ports.”²¹ Churchill did tell Eisenhower that the naval attacks were particularly successful because Enigma regularly revealed sailing dates, routes and cargoes.

As Alexander set the assault on Tripoli for 14 January 1943, Churchill telegraphed to him on December 27th: “Reading Boniface, after discounting the enemy’s natural tendency to exaggerate his difficulties in order to procure better supplies, I cannot help hoping that you will find it possible to strike earlier….”²²

On 5 January 1943, as Alexander and Montgomery planned their Tunisian offensive, Churchill drew the Chiefs of Staff Committee’s attention to decrypts from which he was “pretty sure that the Germans in Tunisia are very short of transport and have not the necessary mobility for a large-scale deep-ranging thrust.” This being so, on noting “in Boniface” the anxiety of the Commander of the Fifth Panzer Army, General von Arnim, about an attack in the southern sector, Churchill asked that the possibility of a southern operation should not be excluded, especially as it would force von Arnim to divert forces to the south, and thus give “the relief we seek” in the northern sector.²³

Churchill was alarmed on February 17th to read two reports about the success of Allied supplies entering Tripoli harbour, and an Enigma message exhorting Rommel to bomb the harbour. Churchill at once urged the Chiefs of Staff Committee to send “remonstrances” to Admiral Cunningham, adding:

He is the best fellow in the world, but he ought not to have said the passage marked in red, which is directly contrary to our policy of minimising the use of Tripoli harbour, and which is calculated to deprive Montgomery of the element of surprise expressing itself in an unexpectedly early attack with greater strength. On the advice of the Chiefs of Staff Committee I purposely lent myself to a very discouraging view of the Tripoli unloadings. But all this is undone. Boniface shows that this is Hitler’s view.²⁴

Churchill was always alert to the dangers of discovery. “You will I am sure,” he telegraphed to Montgomery on March 1st, “Tell even your most trusted commanders only the minimum necessary.” One of the two decrypts to which Churchill had drawn Montgomery’s attention that day showed that, at that point in the battle in northern Tunisia, one of von Arnim’s units, the 21st Panzer Division, had “only 47 serviceable tanks.”²⁵

A single division at Medenine guarded Montgomery’s supply lines. No extra troops seemed to be needed, but on February 28th a decrypt revealed Rommel’s intention to attack Medenine with three Panzer divisions, thus encircling the British forces in front of the Mareth Line. Further decrypts showed that Rommel would deploy 160 tanks and 200 guns.²⁶ Montgomery responded at once, rushing up the New Zealand Division, 400 tanks and over 800 field and tank guns 200 miles along the single tarmac road, switching the balances of forces in Britain’s favour. The RAF, too, alerted by Enigma, was able, just in time, to increase its forward strength, building it up to double that which it was known was available to Rommel.

Rommel, unaware that he had lost both surprise and superiority, launched his attack against Medenine on March 6th. In fierce fighting, the trap was sprung; of 140 German tanks, 52 were counted derelict on the battleground on the following day. Not a single British tank was lost. The German assault infantry, their protective shield itself assaulted, were pinned down and depressed by “a devastating volume” of fierce and medium gunfire. At seven o’clock that evening, Rommel intervened personally, ordering “an immediate cessation of the battle.”²⁷

Rommel’s decision to call off the battle of Medenine was decisive. Had he succeeded in driving back the Eighth Army, which he might indeed have done without his Enigma messages being read, all the Anglo-American plans for Operation “Husky” could have been set back, and a landing on Sicily might even have proved impossible in 1943.

This success for Britain’s most secret source came at a time of sudden fear that the secret was about to be exposed. Churchill’s March 1st warning to Montgomery had been a timely one. Eight days later, on the 9th, the Enigma decrypts themselves revealed that the Germans were suspicious of Britain’s impressive Intelligence. Only later did it become clear that they still did not imagine that their Enigma machine ciphers were vulnerable.²⁸

By March 28th the German and Italian forces were in full retreat, and Churchill sent Montgomery a summary of the recent Enigma decrypts: General Messe’s 164th Division “has lost nearly all its vehicles and heavy weapons,” the 21st and 15th Panzer Divisons “are regathering on heights south-east of El Hamma,” and the Italian commander-in-chief of the Mareth garrisons had asked the 15th Panzer Division “to cover his retreat.” “You should have received all this through other channels,” Churchill wrote, “but to make sure, I repeat it.”²⁹

The battle to drive Axis forces out of Africa was hard fought and prolonged. But following Montgomery’s capture of the Tunisian port of Sfax on April 10th, with more than 20,000 prisoners taken in three weeks, Enigma revealed that the opposition was finally weakening. The next day Churchill telegraphed Alexander: “‘Boniface’ shows clearly the dire condition of the enemy, particularly in fuel.”³⁰

On April 25th Alexander commented: “Enemy is unlikely to be able to stand our prolonged pressure, but he will continue to offer bitter and most stubborn resistance until his troops are exhausted.”³¹ What Alexander sensed in the war zone was confirmed by what Churchill learned from the decrypted German messages. “Boniface,” he telegraphed to Alexander on April 26th, “clearly shows the enemy’s anxiety, his concern over his ammunition expenditure, and the strain upon his air force.”³²

On May 12th, German resistance in Tunisia came to an end. An Enigma signal from General von Arnim to Berlin—decrypted at Bletchley—stated curtly: “We have fired our last cartridge. We are closing down for ever.”³³ Von Arnim himself was captured and 150,000 of his soldiers taken prisoner.³⁴

Sicily and Normandy

The planning for the Sicily and Normandy landings involved two major deception plans. Both depended upon Enigma for the Allied knowledge that the Germans had fallen for them.

The first deception, using the body of a recently dead Briton and forged documents, swapped Sicily—site of the actual landing—for Greece. German troop movements to defend Greece against the expected attack were seen in the Enigma orders. In the words of a member of the deception staff—the London Controlling Section, located just below Churchill’s above-ground rooms in the Board of Trade building—”Enigma told us that the Germans were falling for it.”³⁵

On May 14th, only two weeks after the body had floated ashore off the Mediterranean coast of Spain, a “most secret” message sent from the German High Command to Naval Group Command South pinpointed the “possible starting points” for Allied landings in Greece, specifically Kalamata and Cape Araxos, both of which had been mentioned in one of the bogus letters washed ashore with the body. The German High Command message went on to order reinforced defences at Kalamata and other Greek ports, minelaying and installing operational U-boat bases.³⁶

An Enigma decrypt of this German message reached London that day.³⁷ To Churchill, who was in Washington, Brigadier Hollis at once telegraphed: “‘Mincemeat’ swallowed rod, line and sinker by right people and from best information they look like acting on it.”³⁸

By autumn 1942, planning had begun for a landing in Northern Europe within the following two years. Churchill’s knowledge of what would be involved in such a landing gained immeasurably from Enigma when, on 30 September, Bletchley Park broke the German “Osprey” cypher used by the Todt Organization. This gave an important window into a massive German construction project: the anti-invasion preparations of the West Wall.

Under the expert cryptographic skills of Colonel Tiltman (see Part I, Finest Hour 149, Winter 2010-11, 23), Japanese diplomatic messages whose code had been broken were scrutinised for clues about German coastal defences. It could be time-consuming and frustrating work. In November 1943 the Japanese Military Attaché in Berlin sent a detailed thirty-two-part report to Tokyo about a tour he had just made of the coastal defences in northern France. Eleven parts of this report were solved by the end of December, but the remaining twenty-one parts were not fully decrypted until June 1944. By contrast, a report about the German coastal defences sent to Tokyo by the Japanese Naval Attaché in Berlin on 4 and 5 May 1944, was fully solved and translated by 13 May.³⁹ This gave Churchill and the planning staff valuable insights about what to bomb from the air as soon as possible, and, on D-Day, what to bombard from the sea.

As Normandy planning continued, Churchill was warned that without a series of deceptions, including some in which Stalin would have to participate, no landings would be possible in 1944. On 30 January 1944 the head of British deception operations, Colonel John Bevan, and his American counterpart, Lieutenant-Colonel William H. Baumer, flew to Moscow to explain to Stalin the essential threefold Soviet dimension in the Normandy deception scheme. They made three requests of the Russians:

1) To time their summer 1944 offensive to occur after the cross-Channel landing, in order to confuse the Germans as to which of the two offensives would come first, and to make it impossible for them to withdraw forces from the still-dormant, but imminently active, Eastern Front once Normandy was invaded.

2) To help fake an Anglo-Soviet landing in northern Norway as the first phase in an Allied military advance through Sweden, an essential component of a second front landing in Denmark, and striking southward to Berlin.

3) To appear to be about to mount their own amphibious landing against the Black Sea coast of Romania and Bulgaria.

On 6 March, Stalin agreed to carry out these three deceptions. In the months that followed, as Berlin ordered men and materials to the apparently threatened areas, decrypted Enigma messages revealed that Germans had fallen for them. Without Enigma, there was no way that Churchill could have known that Stalin had either believed in, or carried out, these crucial deception plans.

Integral to the Soviet deceptions was the need to convince the Germans that Calais, not Normandy, was the objective of the Allied armies training in Britain in early 1944. From the moment Enigma revealed the Germans were sold on Calais, the final stages of the Normandy landings could go ahead. Even after D-Day, German Intelligence was convinced that the main thrust would still come at Calais, and held back considerable forces, which Rommel had urgently wished to send to Normandy. Rommel’s appeals, and the High Command’s refusals, were known to Churchill and Eisenhower—and much appreciated by them—through Enigma.⁴⁰

On May 13th the Joint Intelligence Committee warned Churchill and Eisenhower that, on the basis of Enigma decrypts, and reports from agents in France, up to sixty German divisions would be available to oppose the Allied landings in three weeks’ time. After further study of the decrypts, the Committee was able to reassure Churchill and Eisenhower that their estimate fell just below the upper limit that had been set for calling off the landings.⁴¹

Again and again during the preparations for D-Day, during the June 6th landings, and during the advance inland, Enigma decrypts, monitored closely by Churchill, gave precious clues that saved Allied lives. One example: on June 1st an urgent request from Rommel for German Air Force attacks on American positions before a German attack scheduled for 3 pm that day was signalled to the First United States Army with nearly two hours to spare.⁴²

The Bombing of Dresden

Like British help for the Yugoslav and Greek partisans, the bombing of Dresden was also Enigma-driven. Towards the end of January 1945 a series of Enigma messages revealed a German plan to send reinforcements to the Russian front then in Silesia from as far away as the Rhine, Norway and northern Italy.⁴³

On February 1st, through Enigma decrypts, three German infantry divisions from the Western Front were identified on the Eastern Front. “Reports indicate,” Churchill and the Chiefs of Staff were told that day, “that further divisions may be on their way.”⁴⁴

Two days later the Deputy Chief of Staff of the Soviet forces, General Antonov, asked for urgent Allied action “to prevent the enemy from transferring his troops to the east from the Western Front, Norway and Italy, by air attacks against communications.” On the 4th this Soviet request was presented to the Big Three at Yalta,⁴⁵ along with a Soviet Intelligence assessment of the thirty-one German divisions believed to be in transit from the West to Silesia: twelve from the Western Front, eight from the interior of Germany, eight from Italy and three from Norway.⁴⁶

The Anglo-American Combined Chiefs at once agreed to divert some of their bomber forces—then on crucial missions attacking German oil reserves—to attack German Army lines of communication in the Berlin, Dresden and Leipzig region. Nine days later, the Anglo-American bombing began. In the resulting firestorms, tens of thousands of the city’s inhabitants were killed: the direct consequence of information provided through Enigma. (See also Chartwell Bulletin 24, page 9; and “Leading Churchill Myths: Dresden”: http://bit.ly/miyrYK.)

End of the War in Europe

Enigma gave Churchill and his inner circle of military and Intelligence advisers crucial insights until the very end. Sometimes, Churchill had to be reminded of them. On 17 April 1945 he read of a bombing raid three days earlier on Potsdam. He wrote at once to the Secretary of State for Air, Sir Archibald Sinclair and the chief of the Air Staff, Sir Charles Portal: “What is the point of going and blowing down Potsdam?”⁴⁷ Portal replied that it was a report of the Joint Intelligence Committee—based on Enigma—that had noted the shift of German Air Force operational headquarters from Berlin to Potsdam, making it very much a target.⁴⁸

On April 29th, an hour before midnight, as Soviet tanks battled inside Berlin, Hitler sent an Enigma message seeking reinforcements from General Wenck, who was southwest of Berlin facing the British army. The message read: “Where are Wenck’s spearheads? Will they advance?

Where is Ninth Army?”⁴⁹ Thus, even in his final hours, Hitler inadvertently betrayed his thinking and his plans through his own most secret system of communications. This enabled British troops to surround and immobilize the one last hope of a continued fight inside Berlin. On the following afternoon, Hitler committed suicide.

On May 3rd, as the war in drew to an end, a German Enigma message, one of the last of the war, revealed that German moves were being taken to try to forestall a Soviet parachute landing and military advance along the Baltic coast into Denmark. Churchill took immediate action to prevent Soviet forces entering Denmark, ordering Montgomery’s forces to divert from their eastward advance and drive northward to the Baltic. They did so, entering the port of Lübeck with, as Churchill noted to Eden, “twelve hours to spare.”⁵⁰

Thus the last use of Enigma in the war in Europe was not to help Stalin, but to forestall him.

End Notes

1. Decrypt OL211 of 4May41. Churchill to Wavell: Churchill papers, 20/38.

2. Telegram of 6Nov41: Churchill papers, 20/44.

3. “Personal and Secret,” 9Nov41: Churchill papers, 20/44.

3. “Most Secret,” C/8035, 12Nov41: Cabinet papers, 120/766.

4. “Secret and Personal,” 19Nov41: Churchill papers, 20/45.

5. “Personal. Most Secret,” 21Nov41: Churchill papers, 20/45.

6. “Personal and Most Strictly Secret,” 23Nov41: Churchill papers, 20/45.

7-10. Ibid.

11. The message was preceded by a two-letter (digraph) prefix, in this case MK, chosen to imply to any eavesdropper that it was an individual British agent (usually indicated by such a digraph) rather than the German Air Force’s secret radio signals transmitted by Enigma.

12. Prime Minister’s Personal Telegram (hereinafter PMPT) 383 of 1942, 15Mar42: Churchill papers, 20/88.

13. PMPT 393 of 1942, 16Mar42: Churchill papers, 20/88.

14. CX/MSS/945/T12 of 2May42.

15. Geoffrey Pidgeon, Edgar Harrison: Soldier—Patriot and Ultra Wireless Officer to Winston Churchill (Los Angeles: Arundel, 2008), 178.

16. Boniface 1371, T.10, Prime Minister’s Personal Minute (hereinafter PMPM), M.350/2, 6 September 1942: Churchill papers, 20/67.

17. “Personal and Secret.” “Clear the Line,” PMPT 1305 of 1942, 23Oct42: Churchill papers, 20/81.

18. “Bigot,” “Most Secret,” PMPT 1392 of 1942, 29Oct42: Churchill papers, 20/81. “Bigot” was a prefix informing the recipient that the telegram contained material of the utmost secrecy. The decrypts mentioned by Churchill in his telegram to Alexander were QT/4474, 4592, 4599, 4642, 4644 and 4682.

19. PMPT 1420 of 1942, 4Nov42: Churchill papers, 20/82.

20. Enigma decrypts CX/MSS/1698/T.

21. “Private, Personal and Secret,” telegram of 16Dec42: Churchill papers, 20/85.

22. Telegram of 27Dec42: Churchill papers, 20/85.

23. PMPM D.4/3, 5Jan43: Cabinet papers, 79/88 (Chiefs of Staff Committee, 5Jan43, Annex).

24. PMPM D.22/3, 17Feb43: Churchill papers, 4/397A.

25. Decrypt VM 5207.

26. The decrypts were VM 5007 of 0342 and VM 5207 of 1646, 28Feb43: CX/MSS/2190/T14: F.H. Hinsley et al., British Intelligence in the Second World War, vol. 2 (London: HMSO, 1981), 593-95.

27. Major-General David Belchem, All in the Day’s March, (London: Collins, 1978), 147. Belchem was head of Montgomery’s Operations Staff from 1943 to 1945.

28 Hinsley, British Intelligence in the Second World War, 596.

29. PMPT 391 of 1943, 28Ma43: Churchill papers, 4/396.

30. PMPT 498 of 1943, 11Apr43: Churchill papers, 4/289.

31. MA/342, “Personal and Most Secret,” 25Apr43 (received 4 a.m., 26Apr43): Churchill papers, 20/110.

32. PMPT, T.592/3, “Most Secret and Personal,” 26Apr43: Churchill papers, 20/110.

33. David Dilks, ed., The Diaries of Sir Alexander Cadogan (London: Cassell, 1971), 530. Permanent Under-Secretary of State at the Foreign Office, Cadogan had been privy to Enigma since June 1940.

34. The second highest-ranking German prisoner of war after Rudolf Hess, von Arnim was held in Britain until 1947. Many of his soldiers were taken as prisoners of war to Canada and the United States.

35. Jane Bethell, in conversation with the author, 17Jun85.

36. The German General sent to the Peloponnese to prepare for the non-existent assault was Rommel. In the first week of June, a group of German motor torpedo boats was ordered from Sicily to the Aegean; this fact was likewise revealed through Enigma.

37. CX/MSS/2571/T4 of 15May43: published in full, in its original translation, in Michael I. Handel (editor), Strategic and Operational Deception in the Second World War (London: Cass, 1987), 79-80, source, U.S. Army Military History Institute (Reel 127, 5-13May43).

38. “Alcove” No. 217, 14May43: Cabinet papers, 120/88.

39. Secret Intelligence Service archive, series HW.

40. See Martin Gilbert, D-Day (New York: Wiley, 2004), passim.

41. Secret Intelligence Services archive, series HW1.

42. KV 7671 and 7678, quoted in Ralph Bennett, Ultra in the West: The Normandy Campaign of 1944-45 (London: Hutchinson,
1979), 77.

43. Joint Intelligence Committee (45) 31(O), rev. final, 25Jan45.

44. Chiefs of Staff papers, 1Feb45.

45. Transcripts: “Minutes of the Plenary Meeting between the USA, Great Britain, and the USSR, held in Livadia Palace, Yalta, on Sunday, 4 February 1945, at 1700.”

46. This assessment had been transmitted via Bletchley and the British Military Mission, Moscow, to Soviet Intelligence. The message as sent, and the decrypt on which it was based, is in the Secret Intelligence Service archive, series HW/1.

47. PMPM 362 of 1945, 19Apr45: Premier papers, 3/12, folio 3.

48. “Top Secret,” 20 April 1945: Premier papers, 3/12, folio 2.

49. Bennett, Ultra in the West, 234.

50. “Top Secret,” PMPT 771, 5May45: Churchill papers, 20/217.