Fall of Singapore. This was perhaps the worst month of the war for Britain, marked by one unmitigated disaster after another.  The Japanese army fighting their way down the Malay Peninsula reach the Causeway, cut the crucial water supply, and land on the Island of Singapore on the night of 8th February 1942. The British Commander, General Percival, surrenders on 15th February, leading 130,000 men into captivity. This is the greatest catastrophe ever to befall British arms.  At a stroke it destroys the British reputation throughout India and the Far East, leading inexorably to the post-war loss of Empire.  The Japanese lost 3,000 men in the whole campaign, and unknown to the British were desperately short of ammunition when they bluffed us into the surrender. The lack of significant air defence seems to have been one primary cause, though it is difficult to deny that poor leadership and low morale were major factors. It remains almost unbelievable that the big guns were sited to defend against attack from the sea but yet little had been done to build defences against an attack from the landward side, despite this weakness being realised in Whitehall and by General Percival since 1937. He had refused to fortify the Island on the grounds that it would be ‘bad for morale of troops and civilians’.  The lack of adequate Intelligence on the advancing Japanese was certainly a factor, but probably relatively unimportant; we seemed to believe that their force was considerably larger than it in fact was.  Our naval Y team and most of the cryptographers had been evacuated to Colombo, sailing on a warship on 5th January 1942. But a few Army and RAF radio operators and cryptologists, including Arthur Cooper, brother of Josh Cooper who was head of the Air Section at BP, volunteered to stay behind and were able to offer a limited service by listening in to the Japanese naval aircraft and so providing some warning of the time and targets for the air assault. (Arthur Cooper was said to be able to complete the Times crossword in his head). The three cryptographers escaped on 11th February to join the small Army Y station in Bandung on Java.
 
The Western Desert Intelligence War. Excellent Intelligence, provided by Luftwaffe Enigma and Italian Navy C38m decryptions by BP, had been the major factor in forcing Rommel back to El Agheila, enabling the crippling attack on Rommel’s supplies. But now this attack falters because of our naval losses due to U-boats, the intrepid Italian human torpedo charioteers, and the air-attacks on Malta. So Rommel obtains limited re-supply, in particular of tanks and fuel. Though warned by BP from C38m decrypts that two convoys have reached Tripoli, the Eighth Army is caught unaware by Rommel’s opportunistic attack on 21st January. Rommel knows he can catch the Eighth Army unprepared and off-balance from his field intercepts and the Intelligence he is obtaining by reading the encrypted messages from the well-informed US military attaché in Cairo. BP has ceased to be able to read the Africa Corps Enigma key, Chaffinch, since 6th December and the Italian Army high-grade book cypher is becoming difficult to read. For once Rommel has the best of the Intelligence war. His advance is finally halted on the 9th February by his supply position when he has forced the Eighth Army back to the Gazala line, virtually where the British Operation Crusader had started way back on 18th November.
 
Introduction of new U-boat cypher system.  One further disaster strikes the British during February, but the public does not know this, even though it weighs heavily with Churchill and the Admiralty.   On 1st February the German U-boat Command brings into service a new, 4-rotor, version of the Enigma machine. This prevents BP from reading the U-boat signals, and despite Hut 8’s best efforts they were to remain largely unread for many tragic months while the convoy losses mount disastrously.  Admiral Dönitz had been suspicious that the British were reading his submariners’ codes for some months. During the last six months of 1941 he had taken various steps to strengthen his codes.  BP had been able to cope with these but the much more complex way of coding map-references, introduced in December 1941, had resulted in BP frequently being unable to read the positions with any certainty.  The introduction of the new Enigma machine was not unexpected at BP as during the spring of 1941 references in decrypted Enigma signals and captured material had been made to the introduction of a fourth code-wheel, and indeed it had occasionally been employed in error in the months before 1st February.  In December 1941 a German operator compounded his error in using the fourth wheel for one such a signal by repeating it in the three-wheel setting, which of course could be read by Hut 8. This error enabled BP to recover the wiring of the fourth wheel. Hut 8 recognised that sustained success in breaking the four-wheel Enigma key, which they called Shark, would be impossible without the development of a four-wheel bombe, though they did break an occasional Shark key. “After the event they blamed themselves for the fact that, partly from wishful thinking, partly from fatalism, and partly because they were preoccupied with the immediate task of thoroughly mastering the three-wheel Enigma, they had not been more energetic in bringing the vital importance of this need to the attention of their superiors” writes the Official Historian. (It is worth remembering that the author was Harry Hinsley who, at the time in Hut 4, was the direct link between the code-breakers in Hut 8 and the Admiralty’s Operational Intelligence Centre).  But in any case when the warnings were first received the BP management did not wish to divert resources from the three-wheel bombe building programme to this formidable new task As configured, the four-wheel bombe would have to run some 26 times as fast if it were to solve the key in a time comparable to that required to solve the three-wheel machine. At the time of the introduction of Shark BP has been reading virtually every U-boat Enigma message, and breaking the key on the second of the paired days after a delay of only a few hours.  Now, with rare exceptions such as on 23rd and 24th February when Hut 8 broke Shark through a kiss from the dockyard cypher Werft, the only information obtained on the U-boats came from lower grade cyphers such as this.  The damage to our campaign against the U-boats is made even more serious because since September 1941 the Germans had been reading much of the traffic in the main Royal Navy Cypher No 2.  And in December 1941 they began to read the traffic in Naval Cypher No 3, used for Anglo-US-Canadian communications in the Atlantic.  At this time the German U-boats are concentrating along the Atlantic coast of the US, against the easy victims where the coastal shipping is sailing without convoys and unescorted.  So it does not become obvious to the German Naval Command that changing their Enigma machine has had a drastic effect on the ability of the Allies to fight the U-boats.

New Breaks by BP.  It is no real compensation for this major set-back in the Atlantic war, but welcome none the less that in February BP broke two more Enigma keys, that called GGG between Berlin and their Abwehr (Secret Service) posts in the Gibraltar area, and that called Orange 2 used by the SS formations fighting on the Eastern front back to Berlin.

The Channel Dash.  On 12th February the German battle cruisers Scharnhorst, Gneisenau, and Prince Eugen make a dash from Brest up the Channel and through the straights of Dover.  From agents’ reports, from photo-recce, and from Dolphin, the Home Waters Enigma key, the Admiralty is well informed about the state of preparedness of the ships. On 24th December the Admiralty issues a warning that a breakout from Brest is likely at any time. On 2nd February it is concluded that the most likely route for the ships is the Channel passage.  The Air Ministry puts into force Operation Fuller, the plan for dealing with a possible Channel breakthrough. By ill-luck, delays in decrypting Dolphin at this time results in the messages for 10th, 11th, and 12th not being read until 15th February. The convoy of at least 100 German ships sails from Brest at 10.45 p.m. on the 11th.  But despite the air and sea patrols, due to radar jamming and a series of accidents and incompetence’s, largely by the RAF, it is not until 11.25 a.m. on the 12th that news of the detection of the squadron is transmitted from Fighter Command, by which time the ships had already passed Boulogne. The gallant air attacks fail, and the British public is horrified when it is announced that the ships have reached the safety of the German Baltic ports, apparently unscathed. They might have been less upset if they could have been told that the Admiralty knew from Dolphin decrypts that both the Scharnhorst and the Gneisenau had been intending to join the Tirpitz in Norwegian waters but the ships were diverted to Kiel when seriously damaged by mines, especially laid by Bomber Command along their predicted route.  The Gneisenau is further seriously damaged by bombs on the night of 26/27th February and never sailed again. The German Naval Command assessed the operation as ‘a technical victory but a strategic defeat’.

Japanese Language Courses. Now that it is vital that we should read the Japanese codes it becomes obvious that there is a drastic shortage in the UK of suitable people who knew Japanese. Accordingly BP’s Chief Cryptographer, Colonel John Tiltman, asks the London University School of Oriental Studies how long it will take to teach a novice enough Japanese to be useful.  The answer of two years as an absolute minimum being rather too long, Tiltman, who had taught himself enough Japanese to break their codes very effectively in the 1930s, sets up a special intensive six months course, using the veteran, white bearded, naval intelligence officer Captain Oswald Tuck as chief instructor. Tiltman observed ‘For a short but glorious period I achieved considerable personal popularity at both Oxford and Cambridge because I was the only person who wanted classical scholars”. The first course started on 2nd February 1942 organised by the Inter-Service Special Intelligence School with 23 students, located above the Gas Company showrooms in the centre of near-by Bedford. At the end of the course the students knew some 1,000 Japanese characters, and were then put through the BP standard, three week, cryptanalyst course also held in Bedford.  In total 7 courses produced some 175 Japanese linguists, with more experts coming from the School of Oriental Studies and a few ex-consular officials.  Further courses were organised within BP for the Air Force who needed experts with skills in the spoken version of Japanese.  The linguists went to BP, to the Diplomatic Section now back in London, or out to the BP outstations at Colombo, Kilindini, or Delhi

The Proliferation of Keys. The evident proliferation of keys now in progress is a security measure by the German cypher authorities. With more separate keys the enemy has more to break and less material is sent on one key setting each day making it harder to break. It is particularly useful in reducing the damage done by capture in the field – as the security authorities believe this is the only way that the UK is reading their codes. In practice the Germans throw away some of the benefit they gain from increasing the number of keys they use, because the number of times the same material is repeated in a number of different keys rises sharply. These provide excellent ‘kisses’ for the Codebreakers. (For example the Orders-of-the-Day issued by Field Marshal Göring have to be repeated in all the Luftwaffe keys. Was it a New Year’s Day greeting that helped Hut 6 to break the new keys on the 1st January 1942?).  BP is now reaching the point where it is breaking so many keys that it has to drop breaking some of the less important, though it tries to read even unimportant keys at regular intervals, both to check that the material remains unimportant and to ensure its cribs are still current. Continuity is vital in keeping cribs current, and, of course, the more a particular key is read the easier it should become to continue to read it.  Moreover, it is beginning to become very apparent that the vast accumulation of detail that breaking so many messages is producing is of great value in its own right. (One nice example of this arose when in 1944 Dönitz started to use personal data in the indicator of messages to his U-boats believing only a particular captain would know it. On at least one occasion the Hut 4 Index was able to provide the code-breakers with the initials of a particular U-boat captain’s wife!)  

Management Changes at BP.  For some months a battle has been raging in Whitehall over the control of GC&CS and BP.  The Intelligence Branches of the Services were never happy that BP was producing Intelligence as distinct from decrypts, and there was always strife over the use of the vital resources at BP, such as bombe time.  The Codebreakers  ‘Wicked Uncles’ letter of 21st September was certainly not the only warning that Churchill had received that all was not well at BP.  Changes were now instituted that may not have entirely removed the friction, but served in the long run to satisfy the Services that the best was being done for them by those in control at BP.  On 1st February the control of GC&CS was split. Alastair Denniston was relieved of the Directorship of BP and returned with the Diplomatic Section to Berkeley Street; and the remainder of BP was placed under the control of his deputy, Edward Travis.  Alastair felt that he had been harshly treated and there can be no question that it had been his great achievement to ensure that BP had an atmosphere for its codebreakers that was much more like a university senior common room than a military hierarchical command.  But as the number at BP had risen it had become more and more apparent that he was not the man to run such a large & complex Establishment.  Travis was to do this with outstanding success throughout the rest of the war; it is said that the Diplomatic Section under Denniston broke every cypher put before them; but they have never received the renown they deserve.

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