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Updated: 11 Apr 2016


Enigma - The Truth
(compiled from many sources including emails)

The geese that laid the most golden eggs - Churchill about his enimga staff

Eisenhowers Letter ref Bletchley Park

The American Film industry, in it's infinite wisdom, has decided to rewrite history many times in the past.  But their latest examples of historical (hysterical?) facts leave a lot to be desired.  One such film rewrites history with regards to the German Naval Code Machine - Enigma.  The truth according to the film industry, is the American's decided to help out their "poor" British Allies by stealing the machine from the German's to assist us in breaking the German War Codes.  Phooey!  We already had enigma before America joined the war.  The truth was printed in The London Times Supplement dated June 1st 2000. Written by Hugh Sebag-Montefiore. Here it is reproduced. I have since also bought his excellent book. The true story is related later on in this article. The USA were not privy to Ultra decodes until AFTER Pearl Harbour in Dec 1941.

Bletchley Park began its life as a Governmental Department in 1938 as the HQ of the Govt Code and Cypher School, and later renamed the Government Communications HG, or GCHQ. It is now a shrine to the people who worked there and of the Prime Minister who recognised its importance, Winston Churchill. In 1938 Station X went into operation in a small room in a tower of the main building. The aerial was strung across a lawn from the tower to the top of a cedar tree which still stands there to this day.

From this small beginning huts sprang up all over the grounds and at its height, some 10,000 people worked there, 24 hours a day, in three shifts. Amongst the mathematicians ecruitred was Alan Turing, a Cambridge don who, in 1936, described a theoretical computing machine. At Bletchley, Turing designed improived versions of basic machines and put them to work decoding. Known as Bombes, these were nicknamed Bronze Goddesses.  An electro-mechanical machine which was wired into the enigma machine to solve the complex equations and permutations of the codes. Many of these were built and housed in buildings in the surrounding area.

At the beginning of 1940, Turing spent some time in France with the exiled Polish cryptographers, whilst back at Bletchley Park, he has already made a ground breaking invention. It was an electro-mechanical device, which became known as the "bombe"  (Not to be confused with the "bombi" used by the Poles, the "bombe" was a more sophisticated version) which could work out the wheel settings and plug board connections used by the Germans on any given day. Similar to the Polish "bombi", the more sophisticated British version consisted of a series of Enigma machines wired together which could be rotated through each wheel setting to test whether or not a setting worked or could be ruled out. It was here that any similarity to the original Polish version ended. The "bombi" could only work out settings as long as the Germans continued their practice of a double transmission of settings for example a wheel setting would be ABC for that date, when passed though the Enigma it emerged at STD, the message would then begin STD STD. Turing's "bombe" would still work if the Germans dropped the settings to only one eg STD.  Turing once remarked to a colleague that "if I had 10,000 chinamen at my disposal, the bombe would not be required. The "bombe" did in fact, work on finding that were NOT correct, thereby arriving at the correct solution by default. The first "bombe" was installed at Bletchley Park on 18 March 1940 but failed in its task. Gordon Welchman suggested to Alan Turing some modifications, Turing readily agreed, and the "bombe" went through some modifications. Turing then made even further modifications and the machine began to produce results. This was then known to the code breakers as the "spider".

A four rotor machine introduced by the U Boat service in 1942.
Bletchley Parks biggest ally in the fight to decode German codes was the Germans themselves. They refused to believe that their codes could be broken and many operators lapsed into a sense of false security.

Added to this an incredible card index system in which individual germans were filed away and cross referenced to show anything that could be used then, or later. One such german operator, filed away, persistently used his girlfriends initials as a key! Another signal sent a Lt ? to Foggia. Innocent enough? No

Bletchley cross referenced this with previous times this Lt had been mentioned and came up with details of a Luftwaffe move from St Omer in France, to Foggia Airfield in Italy. The Germans had posted an entire Squadron to there and all because a person was posted there via enigma.

To all intents and purposes, the Allies had a person within the German High Command, standing looking over the shoulders of Adolph Hitler - enigma!!

Enigma u-534

The Germans made a glaring mistake in their use of Enigma and this was picked up by the eagle eyes of the staff at Bletchley Park. When it was Hitler's birthday every German unit, in whatever theatre, would send birthday greetings to Berlin. The signals would invariably end with "Heil Hitler" - as did many other communications as well. When spotted the cryptographers had a small insight, with the settings for H, E, I , L, T and R known. It was not much, but every little bit helped. A young Winchester graduate, Pendered, was sent to the factory making the "spiders" where he tested the machine thoroughly, making tweaks and refinements. Then, one day, the "spider" produced the required results, in German, and on 8th August 1940, was installed in Bletchley Park. Bletchley has Abwehr codes broken as early as 1941, they also, through the war, broke the luftwaffe codes and naval codes as well as codes from the German High Command. In 1944 they decoded a message which gave away the HQ of the Panzer divisions in France, Panzer Group West; the same day it was destroyed by RAF bombs, effectively ruining any coordination plans for counter attacks. Eisenhower said later that Ultra saved the lives of many many thousands of allied forces in WW2. England knew more, in many cases, than the German High Command itself.

Before the next section it might be worth visiting my page on the U-33 and the story of the Enigma Wheels here on its own page: U-33 which took place in February of 1940 and slightly precedes the remainder of this narrative.

April 15th 1940 the U-49 was sunk after being forced to the surface by the Royal Navy and an important opportunity to gather intelligence was lost. The Admiralty was livid and gave out some specific instructions to ships commanders.

At 1030 hrs on April 30th 1940, the Destroyer HMS Griffin was patrolling off Norway when a lookout spotted a vessel that seemed at first sight to be a Dutch trawler.  The craft might not have attracted a second glance had it not been that John Lee-Barber, Griffin's Commander, had received a radio signal that another British warship in the vicinity had been attacked by a German armed trawler, posing as a Dutch fishing vessel, which led him to suspect that the ship in his gun sights might not be what it seemed.  Lee-Barber signalled the ship to heave-to.  Then, ignoring the very rough seas, he asked Alex Dennis, his First Lieutenant, to lead a boarding party to check it out.  From a distance the vessel, which had the name Polares painted on its bow, looked like any other neutral trawler, and it was flying the Dutch flag.

But as Alex Dennis and his boarding party rowed closer in their whaler, he saw something that made his blood freeze.  He had caught sight of a deck gun "dressed up" with a canvas cover so that it looked like a rowing boat.  The large number of men milling around on the deck made Dennis feel only more uneasy.  His suspicions were quickly confirmed when he jumped from his whaler onto the trawler deck.  He was greeted by a bemused sailor who blurted out "German Ship" in a guttural German accent.  As Dennis looked around he observed two torpedo tubes concealed under fishing nets, that could have inflicted serious damage on the Griffin had the destroyer attempted to approach the trawler.  Dennis eventually established that the ship was the German Schiff 26, a trawler commandeered by the German Navy that had been on the way to Narvik to deliver ammunition, guns and mines to the occupying German army.

As other members of Dennis's boarding party leapt aboard, one of them let off his pistol by mistake, which startled him but served the purpose of terrifying the Germans.  After that they queued up obediently on the deck so that they could be taken back to the Griffin as prisoners.  Meanwhile another drama was being played out in the sea on the opposite side of the Polares.  The German crew had thrown two huge bags of confidential documents and cipher apparatus into the water.  One bag sank immediately  but the other floated tantalisingly on the surface until Griffin's gunner, Florrie Foord, dived into the water in a last minute attempt to recover it.  He caught hold of the bag but the line to which he was attached broke while he was being hauled on board, and he fell back into the rough sea.  For one ghastly moment it seemed that nobody on Griffin would ever see either Foord or the bag again, but he appeared once more, still gallantly clutching the bag, and gratefully grasped a second line that was thrown to him.

Once again his one handed grip was not strong enough, and he disappeared under the water before bobbing up yet again.  When the line was thrown to him a third time, he managed to secure a makeshift lasso over his shoulders and was hauled up, frozen, with the all important bag.  Whilst Foord was drying himself, Dennis and his men made preparations to sail Polares to Scapa Flow, the British Naval base in the Orkneys. What happened there was to horrify John Godfrey, the Head of Naval Intelligence.  The trawler should have been met by an alert reception committee and placed in a quiet corner, well out of the way of prying eyes, so that the documents on board could be inspected in secret. Instead it sailed into the centre of Scapa Flow - with the Swastika that Dennis and his men had raised provocatively overhead, and swept past the fleets flagship.  Security was so lax that nobody stopped a Universal film crew filming the event. Fortunately the film was confiscated before it could be shown.

The Crucial Capture





Looting was allowed after the boarding party had departed but before Naval Intelligence was able to inspect what was left on the ship, Intelligence Officers found the deck littered with papers, among them Enigma cipher documents and pages from a cipher pad.  These documents, and those recovered from the water by Foord in the freezing waters off Norway, were to enable the naval enigma code to be broken, on May 11 1940, for the first time in the war. The signal pad pages with plain text German and the matching cipher text on them were all that was needed for the "bombe" machines developed by Alan Turing, the Bletchley Park code breaker,  to work out how the Enigma had been set on the day it was captured. Once that had been established, the code could be broken for that day; if the scrambling elements inside Enigma, the three rotors and the plug board, could be set  in exactly the same position as that set by the sender when enciphering his messages, the code breaker merely had to tap out the cipher text on the Enigma keyboard and the letters constituting the German plain text message would light up the Enigma lamp board.

However, the documents recovered provided the key for only 5 days, Apr 22 - 27 1940. The Enigma settings were changed each day, and Bletchley Park still had to find a way of working out the settings for days when there were no captured clues.  Another document from the Polares was to be of much greater significance, for it laid out the procedure  used by senders of messages to indicate to legitimate receivers how to set the scrambling elements in their Enigma machines so that the receivers could unbutton the messages they received.  Knowledge of this "indicating procedure" enabled Alan Turing to devise another ingenious, though long winded, method of breaking the naval enigma code. This method was known as banburismus.  The name for this device came from the town of Banbury, where the sheets were mostly made. This eliminated many "possibles", leaving only "probables". However, it could be used in practice only if he had access to so called "bigram tables" which, in the course of the indicating procedure, were used to convert pairs of letters of the alphabet selected by the message sender into other pairs.  Unfortunately, the bigram tables were not included in the sheaves of paper discovered on the Polares. Bletchley Park's code breakers had to wait almost a year before the seizing of more Enigma codebooks enabled them to make the next breakthrough.

One thing was crystal clear and had to be dealt with urgently. The Enigma codes had to be got hold of once and for all. At the beginning of May 1940, the Germans dropped the double transmission of settings (as mentioned earlier) and the Polish "bombi" would now have become obsolete. After 7 years of reading German codes, the Allies were struck blind. However, in Norway, the Germans continued to use the double transmission, so at least there, Bletchley Park could continue to operate. As things sometimes occur, a "miracle" happened. John Herivel, a 21 year old mathematician, had reasoned, months before, that if all the codes on a particular day were checked, the initial settings of rings could be marked on a chart, the settings with the most marks against should be the code settings for that day! For months this setting was used without success until after May 1940, when the Germans had reduced the settings transmissions, did his idea become important again. After 3 weeks of these attempts, Herivel walked into the Luftwaffe and Kriegsmarine hut to find that the night shift had produced a code! This became known as the Herivel Tip. His tip not only threw up settings but revealed other German errors. On 22 May 1940 the German Air Force code was broken and with very few exceptions, remained broken for the remainder of the war.

Intelligence is only as good as its results however, and to that end it failed insomuch that although the German Blitzkrieg plans lay open for all to read, the superior weapons of the Germans made little difference to the knowledge of what they would do, and when. Coupled with the disbelief in Commanders when handed such intelligence, in many cases, information was simply not passed on.

Admiral Doenitz, on the other hand, was becoming increasingly suspicious when he noticed that a convoy, positions known to the German Intelligence, suddenly "disappeared" from its position and never reappeared. He reasoned that the British knew where his U boats were waiting and had acted accordingly. This could only mean that they could read Enigma messages. He asked about Enigma's efficiency only to be assured by B-Dienst (German Intelligence) that the codes were safe. They had long ago broken the British Admiralty codes and saw nothing indicating such knowledge in British signals. Doenitz was not convinced. The disappearance of U boats, the Schiff26 and two patrol boats off Norway did nothing to alarm the Germans, putting it down to coincidence as 2 destroyers had already been sighted in the vicinity of Trondheim and had suddenly materialised alongside a German trawler. German enquiries revealed nothing to cause them any concern. Meanwhile, the Polish codebreakers, in Paris, realised that nothing was being done with the information being supplied to the French Government. They had been given full details of impending air raids on some car plants in Paris by the Luftwaffe. Dates, times, heights, courses, numbers of aircraft, fighter escorts and targets. And, when the known raids materialised, nothing at all was done by the French. not a single show of resistance was shown, had the French already "given up"? By the time Paris fell, the Poles were in Toulouse, then moved to Oran in Algeria, only to find themselves back in Vichy France in a Chateau, much to the annoyance of the British who felt they were unnecessarily being put into danger by French Intelligence.

In March 1941 another trawler, Krebs, was captured off Norway in the course of a Commando raid by the British Army and the Royal Navy in an attack on the Lofoten Islands. On the trawler were the Enigma settings for the month of February 1941. Using these settings, Turing and his staff were able more or less to reconstruct the missing bigram tables and then to attempt to apply  Turing's banburismus technique.

But it was not to be Turing or any of the other brilliant mathematicians working alongside him who were to make the leap that would allow the code to be broken once and for all.  Turing's banburismus method did not work at first, and the naval enigma code might not have been broken for months had it not been for the lateral thinking of Harry Hinsley, then aged 22, a history undergraduate, who had interrupted his studies to join Naval Intelligence at Bletchley. It was Hinsley who, at the end of April 1941, identified the Enigma's fatal flaw.  Turing had told him that the code breakers were still stuck. So Hinsley knew that the only material he had to work with were the February 1941 decrypts read as a result of the March 1941 capture of the Krebs.  That did not deter Hinsley who, in the course of his medieval studies, had become adept at making the most of scant historical evidence.  While he was pouring over the messages once again, it dawned on him that he had missed something that had been staring him in the face for days; the same enigma code books used on the heavily armed U Boats that were so difficult to capture were also being used aboard isolated and unprotected trawlers.  The trawlers, which were transmitting weather reports to the Germans, were in their turn being sent naval enigma messages.

Although the weather ships were not enciphering their weather reports on enigma machines, they had to have one of the machines on board if they were to decode the enigma signals transmitted to them.  This was an act of almost unbelievable folly since, if the code books could be captured from one of these vulnerable trawlers, the naval enigma system, used by the U Boats, Nazi Germany's most effective weapon, would be compromised.  Hinsley had discovered Enigma's Achilles heel!  He immediately told the Admiralty what he had found out.  Then he explained how the discovery might best be exploited.  If the Royal Navy were to send a warship to board one of the weather ships, the German crew would doubtless have time to throw their current enigma settings into the sea before they were boarded.  However, Hinsley was almost certain that the next month's Enigma settings would be locked in a safe.  That being the case, he reasoned, if the Germans were frightened sufficiently by the warships guns, the locked up codebooks might well be forgotten when the ships were abandoned.  The Admiralty accepted Hinsley's hypothesis. At the beginning of May 1941, no fewer than seven destroyers and cruisers were sent to the northeast of Iceland where the Munchen, one of the weather ships, was operating.  In the course of the raid, the weather ship, and the Enigma settings for June 1941, were captured.  As a result of this planned capture, and not as a result of the fortuitous capture of the U-100 two days later, naval enigma messages transmitted during June 1941 were read almost as soon as they were sent.

But halfway through June 1941, Turing had to ask for Hinsley's help again. The German's had replaced the bigram tables worked out so painstakingly by the British code breakers. This was a serious problem for the code breakers. Since Bletchley Park needed to read Enigma messages for about a month to be able to construct the new tables, and since the code breakers only had Enigma settings for the two week period ending at the end of June, there would be a code breaking blackout unless further settings were captured.  But Hinsley and the Admiralty were concerned that capturing another weather ship might give the game away. There was no point in seizing the settings if the Germans immediately altered them because they knew they had been captured.  So there were agonised discussions about what to do before the Admiralty decided to take a risk.  On June 25th 1941 four warships set out from Scapa Flow to capture the codebooks from the Lauenburg, another weather ship operating north of Iceland, which Hinsley had selected.  On the way Kim Skipwith, the Commander of the Destroyer HMS Tartar told his men that they were looking for a meteorological ship that was providing the Luftwaffe with weather reports. "If you chaps don't want your homes to be bombed, you'd better find her", he told them. He then warned Tom Kelly, his chief gunners mate, that when they found the ship he would be instructed to open fire but he must on no account hit the target. "That'll be very easy", Kelly retorted impudently. "I just want to encourage the crew to abandon ship, pronto", Skipwith explained.

At about 7pm on June 28th, a lookout on Tartar shouted "There's something over there, behind that iceberg!".  That something was the Lauenburg. Shortly after Kelly's gunners opened fire, two lifeboats full of the Lauenburg's crew were seen being rowed away from the weather ship.  Minutes later Tartar steamed alongside and a boarding party led by Lieutenant Hugh Wilson leapt aboard.  They were joined by Allon Bacon, a Naval intelligence officer.  "There's nothing much here", Wilson told him.  Nodding dismissively at the disorganised piles of paper lying in the charthouse and on the deck, he added "You don't want this rubbish do you?". To which Bacon replied that he wanted it all and declared himself satisfied only when all the paper had been bagged and taken to Tartar.  Only then was Kelly instructed to fire on and sink the Lauenburg.  On the journey back to Scapa Flow, Bacon closeted himself in the Officer's day cabin to sort out the documents. Wilson looked in from time to time to offer him a cup of gin, but Bacon refused to be distracted. When Tom Kelly popped his head round the door and asked Bacon if he had found what he was looking for, Bacon, who had disappointed the Task Forces Commander by not bringing back an enigma machine said, "No, but I've found something a damn sight more important".  Among the mass of charts and signaling papers he had come across three loose sheets that Hinsley had hoped he would find. Two of these were headed Steckerverbindungen  (plug connections) and one was a list of the Innere Finstellung (inner settings) i.e.: the enigma wheel order, and the settings for the rings around the wheels that could be altered only by fiddling around inside the Enigma machine.

The Lauenberg - a photo taken from HMS Tartar (below) the landing party clearly visible

It was thanks to these documents that naval enigma messages were read throughout most of July 1941, and also that the latest set of bigram tables were finally reconstructed, which opened the way for Turing and his team to exploit his banburismus procedure.  From the beginning of August 1941 Turing and his colleagues were able to break the naval enigma code using the banbarismus procedure with an average delay of about 50 hours. For the moment the battle for the naval enigma code was won.  Enigma could put a message into code in over 150 MILLION MILLION MILLION different ways. Hitler’s Fatal Mistake?
Almost unnoticed by the depressed British public several events in August 1941 provide the first signs that the tide may be turning.  Hitler orders a halt to the offensive towards Moscow, in order to reinforce the drive to the important oil-fields in the South. Despite the continuation of the German advances in the North to cut off Leningrad and in the South into the Crimea, the decision to delay the advance on Moscow was seen in due course as leading to the failure to take Moscow in 1941. In the Atlantic the Allied shipping losses fall dramatically, due primarily to the mastery by BP of the cypher used by the German submarines enabling the Admiralty to route the convoys round the wolf-packs.  The first of the North Cape convoys carrying desperately–needed supplies to Russia arrives safely in Murmansk.  Across the Atlantic Churchill confers with Roosevelt. The Atlantic Charter that emerges may be little more than rhetoric, but this first building of the friendships between the leaders and their staffs that are initiated on board the ships off the coast of Newfoundland is to bear fruit in joint endeavours which became fully operational once the USA entered the war with the Japanese assault on Pearl Harbour four months later.  That much heralded yet surprise event can now be seen to have been an almost inevitable consequence of the US/UK decision to impose an embargo on supplies of oil to the proud Japanese.
When the USA entered the War, american cryptographers came to work at Bletchley. A US Brig General, who knew about enigma, foolishly hitched a ride on one of Gen Doolittle's bombers on a mission to France. It was shot down and the General was imprisoned in a Stalag. The germans has someone in thier hands who knew all about enigma and the General lived in fear of giving the secret away, as he knew he 'talked in his sleep'!!! After the war he was reduced to the rank of Colonel, but Doolittle, the hero of the bombing of Tokyo, was never punished. Stalin had an 'eye' at Bletchley Park. A British Staff Officer, John Cairncross, was a soviet spy. He collected up debris from the floor of the hut and sneaked them out to pass onto a Soviet diplomat in London. This traitor fed much information to the soviets and it is a miracle that none of it fell into German hands, it could have altered the war and done very severe damage. Cairncross admitted to spying in 1951 after MI5 found papers in Guy Burgess's flat with a handwritten note from him, after Burgess's flight to Moscow. He was never prosecuted (sadly). He died in 1995.

Extract from BP Newsletter Sept 2011.

Alan Ross worked at Bletchley Park on a section that dealt with the German code RHV which was used primarily for small vessels using the Norwegian coast and by other vessels, including U Boats, not fitted with Enigma machines. RHV means “Reservehandfahren” which is, I think, self explanatory. This code was broken for the first time in June 1941, the U-110 had on board some RHV codebooks. But, as we are becoming used to reading, the Germans had made an error otherwise this could not have been read. They did not, for some reason, change the codes as often as say, enigma (Key M was the German name for the machine). RHV translations were not really of any help to the Royal Navy but they were very helpful to Bletchley Park. Messages sent via Enigma were, very often, repeated in RHV – if the RHV cipher was broken then the plain text could also be used as a crib for the still obstinate Naval Enigma.

The code used by naval dockyards, small ships in dockyards and by harbours was known as Werftschlussel. Schlussel being “key” in German. However, it was also used by capital ships and warships to communicate with these yards. Werftschlussel was broken in 1940 and made a significant contribution in October 1941. Bletchley Park was baffled by a new code on the 3 – 5 October 1941 used by U Boats to communicate to the docks.  Bletchley Park used the Werftschlussel as a crib, discovered that the U boats were using a new code. Doenitz had introduced a new key amidst his concern that U Boat positions were being compromised. During this time Bletchley Park was taking in new recruits and new fresh eyes began spotting German errors. One of these recruits, a chap called Jack Good, actually dreamt that an order of code had been reversed. When he awoke he went and tried it out and it worked! In November 1941 the Germans replaced the Bigram sheets with new copies, thereby depriving Bletchley Park of the fuel for the banburismus procedures. This did not stop decoding but time taken to achieve the required result was extended to unacceptable proportions. The problem was alleviated somewhat as Bletchley Park could use 15 bombes.

In December 1941 plans were in place for two consecutive raids on Norway, one in the Lofoten Islands. Naval Intelligence was instructed to accompany these raids in order to assist Bletchley Park with the acquisition of new code books and, hopefully, bigram sheets. Whilst the Navy was conducting street fighting on the island of Vogsoy, Alan Bacon, of Naval Intelligence was searching the armed trawler Fohn, now abandoned, and he found new bigram sheets, enigma setting tables and five enigma wheels. In fact he filled two sacks with relevant information. Another Armed Trawler, the Donner, taken at sea, yielded a complete enigma machine, more bigram tables and 5 wheels.

Further up the coast another raid was taking place and HMS Ashanti had a German Trawler cornered. Due to an error on board the Ashanti, nobody had ordered her main guns trained on the trawler. This was noticed and someone ordered her guns trained upon the Trawler, where the German crew was being held at gunpoint on deck. The sudden movement of the ships armament startled the crew, who thought the trawler was about to be blasted to kingdom come, causing the crew to jump ship in a hurry! A shell from one of the guns was actually fired; it passed straight through the radio room and out the other side, causing the radio operator to abandon ship without calling for help. When boarded, an enigma machine, bigram tables, code books were all transferred to Ashanti, the trawler was then sunk. Both raids had yielded very valuable prizes and by 1st January 1942, all had arrived safely at Bletchley Park. Back in business! But the success of the raids was short-lived when, in February 1942, the Germans introduced the 4th wheel to Enigma.

This downturn, coupled with the breaking of the Royal Naval Cipher 3 by B Dienst, enabled the U Boats to enjoy a period of relative success as Doenitz could direct his boats to convoys but the British could not divert them away.  The breaking of the Royal Naval codes was a mixed blessing in that it protected the knowledge that the British were “blind” from the Germans, thus ensuring that the secret remained so for a while longer.

HMS Petard

HMS Petard

Britain was also very reluctant to pass on information to the USA due to concerns over security at the American end. The Americans wanted to know why information was drying up but Britain did not inform America of the 4th wheel and subsequent lack of decoded information. This reluctance was well founded as shall be seen later on. By April 1942 Britain told the Americans about the lack of information due to the new 4th wheel being added to Enigma and therefore unreadable and on 13 May 1942, allowed America access to the enigma files. The Americans, armed with blueprints, began construction of their own “bombes”. The Americans told Britain at the same time that they had cracked the Japanese diplomatic “purple” codes. They could read military codes as well. Autumn 1942, the U Boats had the upper hand in the Atlantic Ocean. Doenitz now had 126 U Boats operational. Things looked grim until once again, a U Boat came to Britain’s rescue. It was October 30th 1942, and off Port Said, the U Boat U-559 had been spotted off the Egyptian coastline by a Sunderland Flying boat’s radar screen. No less than 5 destroyers were dispatched to the “kill”. One of these was HMS Petard captained by a man who had a burning ambition to take a U Boat intact! Some of his crew had burning ambitions towards him as well, he drove them quite hard!

The U Boat proved to be a difficult opponent, diving too deep for the depth charges to attack. At that time depth charges were unable to attack deep lying submarines which could dive a lot deeper than British experts imagined. One of the crewmen, and it’s a shame we do not know his name, had the bright idea of putting soap into the holes of the depth regulator, thereby causing the depth charge to detonate much deeper than planned. The soap worked and it forced the U-559 to move away, giving ASDIC operators on the surface a stronger echo. Repeated attacks took its toll on the beleaguered submariners, they were cracking. Grown men broke down in tears under the incessant hammering on the hulls of the explosions. U-559 was also leaking badly. The incoming water was upsetting the delicate balance of the boat and, after discussions; the order was given by Captain Heidtmann, to surface. There was precious little time left. Yet again, under the intense pressure of battle, a German (Gunther Graser) or one of his section, made a serious mistake. Whilst evacuation was under way, they were supposed to open vents to fill the diving tanks, causing the submarine to dive again but someone had not removed the levers retaining pins which bent and the levers became jammed. The Captain of HMS Petard, Thornton, sensing his prize, shouted at his boarding party to search every single sailors pockets, he knew what he was looking for.

Lt Fasson and Able Seaman Grazier
Petard - has its own page

Memorial to Able Seaman Grazier, Tamworth
16 year old Canteen Assistant, Tommy Brown, (one of many who lied about their age) had joined the boarding party  along with Lt Anthony Fasson and Able Seaman Colin Grazier. Tommy went into the conning tower and down into the flooding U Boat. The lights were all still on. Fasson found some water soluble paperwork in the Captains cabin, he passed them to Tommy and he managed to keep them dry despite water coming in through a shell hole and he climbed out and handed them to a waiting whaler. He also helped to remove all the codes from the submarine. The Lieutenant could not remove the enigma machine as it was bolted quite firmly in place. Tommy remembers the Officer hammering away at the fittings in an attempt to break them. Time was short. The water was getting deeper and deeper and Tommy made three trips to the boat with codes and books. Fasson had returned to the control room to wrench a radio or radar set from its fixings but by this time the water inside the U-boat was knee-deep and rising. Brown, now on top of the conning tower, shouted 'You had better come up!' down into the U-boat as its afterdeck was well underwater. As Grazier and Fasson started up the ladder, the U-boat suddenly sank. Brown jumped clear, but U-559 made her last dive taking Lt Fasson and Able Seaman Grazier with her. '
The documents retrieved from U-559 reached Bletchley Park on November 24th. They proved to be the Wetterkurzschlussel and Kurzsignalheft, which yielded a priceless set of cribs. On December 13th, a crib obtained using the Wetterkurzschlussel gave a key with M4's rotatable Umkehrwalze in the neutral position, making it equivalent to a standard Enigma and thus potentially breakable on existing bombes. Six bombes were plugged-up accordingly and run. Later that afternoon, after a blackout of ten months, the naval section at Bletchley Park telephoned the Admiralty's Operational Intelligence Centre to report the break into SHARK. Within the next hour the first intercept chattered off the teleprinter indicating the position of more than a dozen U-boats. A stream of intercepts followed allowing the rerouting of convoys around the waiting wolfpacks. Allied shipping losses in the Atlantic were consequently halved in January and February 1943 and, perhaps even more vitally, procedures were developed which facilitated the breaking of SHARK for much of the remainder of the war. Fasson, Grazier and Brown's action consequently saved millions of tons of Allied shipping and tens of thousands of Allied lives. As eminent naval historian Ralph Erskine has put it: 'Few acts of courage by three individuals can ever have had so far-reaching consequences.'

Ineligible for the Victoria Cross since the action did not take place under enemy fire, Fasson and Grazier were each posthumously awarded the George Cross. Brown, who survived, was awarded the George Medal but died in 1945 attempting to rescue his sister from a house fire. Despite this and the memorial sculpture to the three in Grazier's hometown of Tamworth in Staffordshire; Fasson, Grazier and Brown's action has never received the widespread public recognition which it deserves.

Thornton ordered his men not to utter a single word about this to anyone, it was to remain secret. But 2 men from an accompanying destroyer were later overheard by police talking about the escapade in a public bar. They were whisked away and told in no uncertain terms to keep their stupid mouths shut. It turned out to be an important find as the new weather reporting code books were amongst the papers and could be used as cribs for other codes, including Enigma. But once again, they had got away with it and the Germans knew nothing about the fate of the U-559. The documents retrieved from U-559 reached Bletchley Park on November 24th. They proved to be the Wetterkurzschlussel and Kurzsignalheft, which yielded a priceless set of cribs. On December 13th, a crib obtained using the Wetterkurzschlussel gave a key with M4's rotatable Umkehrwalze in the neutral position, making it equivalent to a standard Enigma and thus potentially breakable on existing bombes. Six bombes were plugged-up accordingly and run. Later that afternoon, after a blackout of ten months, the naval section at Bletchley Park telephoned the Admiralty's Operational Intelligence Centre to report the break into SHARK. Within the next hour the first intercept chattered off the teleprinter indicating the position of more than a dozen U-boats. A stream of intercepts followed allowing the rerouting of convoys around the waiting wolfpacks. Allied shipping losses in the Atlantic were consequently halved in January and February 1943 and, perhaps even more vitally, procedures were developed which facilitated the breaking of SHARK for much of the remainder of the war. Fasson, Grazier and Brown's action consequently saved millions of tons of Allied shipping and tens of thousands of Allied lives. As eminent naval historian Ralph Erskine has put it: 'Few acts of courage by three individuals can ever have had so far-reaching consequences.'

It was not until December 1942 that another breakthrough occurred, again, through German errors. The 4th wheel, it was discovered, was always set to A with its ring setting to Z; which meant that only 3 wheels were still being used. Due to 'apparent' operators laziness the 4 wheel enigma was only being used as a 3 wheel machine! But this could also have been that, when sending weather information or something known as B Bar messages, the fourth wheel was not required.

Seven months later, King George VI was handing out medals to the Petard crew and he asked the ASDIC operator, Ken Lacroix, “We are still not allowed to discuss this are we?” “No Sir, it’s still a secret” “Well, congratulations”, said the king. (See footnote on page 2 on Ken Lacroix). On the 17th February 1943 came another breakthrough with the forcing to the surface of the U Boat U-205 off the coast of Libya by HMS Paladin and HMS Gloxinia. A large amount of documents were removed from the submarine. HMS Gloxinia attempted a tow but the U-205 went down in the bay by Ras el Hillal.

In the Atlantic events were reaching their peak in the battle against the U boat. During March 1943 627,000 tons of shipping was lost to the U boat. On 19th March, code breakers got into the code once again, with the help of books taken from both the U-559 and the U-205. Even a bigram sheet change by the Germans made little difference as Bletchley Park had no less that 70 “bombes” now working, running codes.

After March 1943 All Allied plans for tackling the U Boats came together in unison and the peak of the Battle of the Atlantic was passed. Anti submarine hunter killer groups, like Captain Walkers ships, long range aircraft closing the gaps over the ocean and quicker decrypts of Enigma were the main causes. Better defended convoys too aided the cause. In Africa, enigma decodes enabled Montgomery to inflict a massive defeat on Rommel by reinforcing a weak defensive section in time to combat a German offensive. The defeat was so emphatic that the Afrika Korps sent messages back to Berlin hinting at “code betrayal”. At sea, ships were equipped with the latest centimetric radar, which U boats could not detect. Ships could now take on the U Boat on their own but long range aircraft also were fitted with the same radar. Many aircraft flew from the increasing number of escort carriers becoming available.

May 1943 saw a significant downturn in the numbers of ships being sunk by the U Boat, 264,000 tons compared to 600,000 in March. Doenitz noted that this was at a loss of 31 U Boats, which was unacceptable. Doenitz ordered all boats out of the area to southwest of the Azores – they had lost the Battle of The Atlantic, although the battle would continue to the last days of the war, it was effectively game set and match to the Allies. On 21st September, Churchill revealed to a cheering House of Commons that in the previous 4 months of the war, not one single ship had been lost to a U Boat in the North Atlantic. The corner had well and truly been turned.

Part of the Petard incident above is also transcribed here: Capturing Enigma: How HMS Petard Seized the German Naval Codes by Stephen Harper and Seizing the Enigma: The Race to Break the German U-boat Codes 1939-1943 by David Kahn. I have not read either but found a cross reference on another site.

The U559 was commissioned 27 Feb 1941, a Hamburg boat, and completed 10 patrols. Responsible for the sinking of 4 ships, a warship, and 2 others total losses. 32.30N, 33.00E is the position where it was sank.  The destroyers involved were HMS Petard, Pakenham, Hero, Dulverton & Hurworth. An RAF Sunderland from 47 Sqn. 38 crew members were rescued and 7 dead. That's 9 dead including our two gallant heros Fasson & Grazier.

I am grateful to Ralph Erskine for some enlightening facts about enigma in general and, in particular, the role of Petard and her crew.

See also: Tommy Brown:

Lt Fasson:

The Role of Enigma in the Sinking of the Scharnhorst


Due to the withdrawals of U boats from the Atlantic, the role of Enigma diminished but was counterbalanced by the assistance it gave to a grateful Royal Navy in the Arctic Ocean. Not only did the U Boat threat remain but also the convoys to Murmansk and Archangel were within range of Norwegian based German bombers and also surface ships were in Norway’s Fiords. Tirpitz was out of action, crippled in Trondheim Fiord and the Lutznow had fled back to German national waters. But, still alive, and very much kicking, was the Scharnhorst. Her presence tied up much of the Home Fleet in Arctic waters. Admiral Fraser was receiving enigma reports on the state of readiness of Scharnhorst. Fraser, on board Duke of York, personally took convoy JW55A to Kola in December 1943. Much to the surprise of the Russians. He then returned to bring convoy JW55B which was due to leave Loch Ewe, Scotland on 20 December 1943.

As JW55B sailed Fraser received notice that Scharnhorst was on 3 hours readiness, and on Dec 21st was back on 6 hours notice. Then he was informed on 22nd December that, on 21st December, Scharnhorst was back up to 3 hours notice. Enigma decoding had become relatively fast but there were delays, counted in hours, when codes were changed. News received on Dec 23rd was such a case.

Part of the German coding system on enigma was the Offizier Procedure for anything of utmost importance, one off messages. The method involved an officer setting up an enigma with the same settings as normal, but using different plug board settings. The list of settings changed only once a month. After encoding his message, the transcript was then handed to an operator who encoded it yet again.

But Bletchley Park managed to work around even this extra hurdle using cribs which often contained the word “fort” or “continuation” (fortsetzung) and the time of origin of each message. Leslie Yoxall, 26 years of age, a mathematician, exploited yet another German oversight. As soon as the board settings were discovered, they were valid for the remainder of the month. Yoxall managed to decode a message containing only 80 characters, whereby the normal message length required was in the region of 200.

Nevertheless, it took 48 hours to inform Fraser that, on Dec 22nd, Scharnhorst had been told to make ready for sea. This coupled with enigma news of increased Luftwaffe reconnaissance warned him that something was about to happen. If the Offizier Code has been more readily decoded he would have heard that “Battle Group is to be at 1 hours notice from 1300 hrs 25th December. Scharnhorst to acknowledge”. It took 31 hours for this message to reach Admiral Fraser on the battleship Duke of York. But by this time it was too late to influence events.

Even when a message could not be decoded it was not the end of matters. Harry Hinsley, Bletchley Park, used a method that, if messages were more frequent than normal, then something really major was occurring, or about to occur. He phone Denning in the OIC at the Admiralty and related this fact. When he had first arrived at this conclusion, nobody took any notice of him, and the Royal Navy lost HMS Glorious and several destroyers to Scharnhorst and Gneisenau.  Now, when Harry spoke, people listened.

Fraser was informed that Scharnhorst has sailed when a message warned a patrol vessel to expect Scharnhorst to pass her at approximately 1800 hrs 25th December. Fraser recorded that, at 0339 hrs 26th December, he received a signal stating that Scharnhorst was at sea. Fraser was too far from convoy JW55B to be of any use. He broke radio silence to order JW55B to steer to the north, away from Scharnhorst. The Germans picked up Fraser’s messages but did nothing to inform Scharnhorst or to recall her. Even when a Luftwaffe reconnaissance aircraft called in to report “5 warships, one apparently big” to its base still the Germans did nothing. The aircraft has found Fraser but not Vice Admiral’s Cruiser Group which was already entertaining Scharnhorst. Scharnhorst escaped one encounter but inexplicably turned directly into the Cruiser Group again and eventually ran into Duke of York. The full story of the Scharnhorst can be found on my web page: Scharnhorst  and back at Bletchley Park as Pondered read the penultimate signal from Scharnhorst to base timed at 1819 hrs which he sent onto the Admiralty at 2347 hrs, he wondered if the message intercepts had had any bearing on the outcome. Scharnhorst succumbed to the guns of the Royal Navy at about 1945 hrs that same evening.

Scharnhorst (above) & Scharnhorst prisoners coming ashore at Scapa Flow

Duke of York firing on Scharnhorst

Maintaining the Secret

Whilst events like the sinking of the Scharnhorst were unfolding. Events in France and elsewhere were also unfolding. The French Intelligence, instrumental in getting enigma out of Poland into British hands, were playing a dangerous game in that the Poles were still on French soil and could be caught at any time. They were in a chateau in Vichy (unoccupied) France. And some members of French Intelligence were active Resistance fighters. They all had one thing in common, they all knew that England had enigma. Their continued liberty was something causing London concern.

One of these agents had been captured and had informed the Germans that the Poles had had Enigma for 10 years before the war but did not bring England into the topic. He revealed Schmidt, the German who had sold Enigma’s secrets to the French for profit. Schmidt was arrested but had committed suicide in Prison. In August 1943 the German Intelligence, B Dienst, in Switzerland, filed a report about Enigma. It caused severe panic in U boat HQ and consternation in Berlin. It stated that “over the past few months, Germany’s naval ciphers, which are used to provide operational orders to the U Boats, have been successfully broken. All orders are being read currently. The Source is a Swiss American in an important position in the US Navy Dept”. German Naval Communications refuted the report, again stating that it was impossible! Doenitz wrote in his diary that from 12 June – 1 August, 13 of 21 U Boat meetings had been undisturbed, but between 3 – 11 August 10 meetings had taken place and ALL had been disturbed.

The mysterious Swiss American’s intelligence became a concern when, on August 18th 1943, more details were filed by B Dienst. This person was “related to the Military Attaché and often traveled to London with the US Navy delegations” and “a special office had been set up for code breaking since war started, for several months it had been very successful” – those who could have done something about it also knew of the refusal to believe it could be happening, citing the numbers of permutations required on the wheels and message settings alone, let alone the plug boards. This voice in Washington had told the Germans about the existence of Bletchley Park but the Germans would not believe it. The previous British reluctance to share information with America had proved to be correctly founded, the Americans simply could not be trusted and these leaks bore this out.

The Germans were so sure of their infallibility that their errors were really quite amazing. Bletchley Park found yet another of these errors when messages sent out on one of the nets, codenamed Dolphin, used by the arctic U boats, were repeated on another of the nets codenamed Shark, used by the Atlantic U boats.  The breaking of Dolphin intercepts became a high priority to enable decode of Shark messages. In July 1943 a second Gamma wheel was introduced, and its associated thin reflector. Either of these two new elements could be inserted instead of the normal 4th wheel. This was used on the Atlantic Shark net. Luckily (!) during the short period Shark became unavailable, U boats were not operational in the Atlantic, and Royal Naval Submarine tracking rooms were able to use HF/DF (High Frequency Direction Finding) to pinpoint a location of a U Boat or U boats. Shipping losses rose from 20 ships in June to 46 ships in July. And, once again, Mavis Baty, in the main, was triumphant in breaking the latest code. This is the same lady who had read the Italian codes prior to giving Admiral Cunningham a great victory in the Battle of Matapan and she used a similar method to crack the Shark code.

On August 29th Bletchley Park reported a 100% decode of all traffic from 1st – 18th August. So much so, that redundant “bombes” were redirected to deal with Army and Air Force codes. The Americans by now where building their own “bombes” but ran into trouble by trying to rush it where Bletchley Park “walked”. The US Navy were sending Bletchley Park Shark intercepts, and others, from about 1 Nov 1943. After the beginning of 1944 and the acceptance of what Bletchley Park was saying, results began to pour in. The American section was known as Op - 20 – G.

With the arrival of 1944, Enigma was to switch its attentions to the U Boats in the Indian Ocean. Many of these had arrived there from being released from the Atlantic. Here in the Indian Ocean they were replenished from tankers such as the Charlotte Schliemann. Thanks to an Enigma intercept, she was found and sunk. Her replacement, the Brake, arrived and the Admiralty was reluctant to attack as it could again compromise Enigma intercepts but the heavy signal rate from and between U Boats alleviated that particular concern as they could have been found by normal means and so the Brake was to be put to the sword also. Once sighted by aircraft, HMS Roebuck was sent in to sink it. HMS Roebuck began firing from a range of 9 miles and an hour later the Brake was sunk. A U boat in the vicinity later reported in that it presumed refueling point had been basically compromised. They had seen the aircraft and assumed a large carrier in the vicinity. It was noted in Germany that “it can be assumed that the enemy knew about the meeting point either by reading our signals or information provided by a traitor”.

Doenitz then instructed U boats to ignore code books and to use crew surnames and/or house numbers. For example, in March 1943, the crew of the U123 required the standard Offizier Settings to be modified by adding  (modulo 26) the house number of the home address of Seaman Lelanz to each of the Offizier plugboard settings. U Boats began to use individual Enigma cyphers (Sonderschlussel) for each boat in November 1944, these were virtually unbreakable.

In March 1944 the Allies were reading of a meeting point in an area west of Cape Verde, off West Africa and ordered all ships to avoid the area so as not to compromise Enigma. But American vessels ignored the warnings and sank 2 U Boats. Admiral Cunningham (Now First Sea Lord) and Admiral King (USN) had a very heated discussion. And once again luck was on the side of the Allies, with the Germans assuming increased aircraft activity and airborne radar as being to blame. At the same time the U-744 had been found 200 miles south of Iceland. Her Captain had fired on what he thought was a solitary destroyer before diving deep. They heard an explosion and assumed a hit, coming back up they were shocked to hear the thunder of screws bearing down upon them, it was another 6 ships! They subjected the U-744 to an all night attack and by morning the crew was suffering from oxygen starvation, lying on the floors, and the batteries had almost expired. The U Boat simply had to surface, 29 hours after the attack had begun. As it surfaced the warships opened fire taking both the Captain’s legs off, and he fell unconscious, onto the deck. Scuttling charged were being set as a boarding party from HMCS Chilliwack came alongside. A crewman, Bert Martin, had the code books and latest charts stuck inside his life jacket when a large wave hit the U Boat, knocking him overboard, never to be found. Enigma codes had been in allied hands and the Germans failed to heed the warning from surviving crew members who sent back word from the POW camp in Canada. Eventually they decided that the U boat had sunk before the boarding party had got on board. A misleading newspaper report helped matters by stating that the U boat sank “as we came alongside”. The secret was still preserved.

On 20th June 1944, more code books and documents arrived at Bletchley, this time courtesy of the US Navy when they captured the U-505. However this did not go down well with London as the crew had seen the books etc being removed. Heated and speedy discussions ensued before the crew was declared “dead” at sea and were not even returned to Germany until 1947. They were hidden from Red Cross visitors and appeared not to “exist”. The U-505 now resides in Chicago after being towed across the Atlantic by the USS Guadalcanal and tugs sent over.

On the night of the invasion of Europe, 6th June 1944, the crews at Bletchley Parks sat and waited for the inevitable rush of intercepts when the invasion was discovered. Mastery of the German codes was practically complete by this time. The code breakers waited anxiously for signs of retaliation and movements to attempt to counter D Day. A weather station in the Bay of Biscay had for months been sending out messages all starting with the same sentence “Weather forecast for Biscay” which was an ideal crib and was used for every code change.  The Germans even sent out a rebuke to the station which had no effect. Harry Hinsley, by now assistant to the Station Chief, sat looking at a map of France. Another fact that speeded up the decoding of intercepts had been found in Washington. The Americans noted that when a wheel had been used it was not put back into the system for 6 months, thus greatly reducing the number of variations required to crack a new code. Yet another German mistake exploited to the full by the Allies.

Harry’s opposite number in SHAEF (Supreme Headquarters of the Allied Expeditionary Force) would ring him from time to time to see if anything had appeared.  His first German Naval coded message was decoded just about 0300 hrs 6 June. Soon afterwards the phone rang and a lady asked if that was Harry. Yes he said, the lady replied that the Prime Minister would like to speak to him. “Has the enemy heard we are coming yet” the voice asked him. Harry told the PM that the first signal was just in and that it was on the printer now.  The pm put down the phone without a word.  90 minutes later the PM was on the phone again, How’s it going? He asked Harry. They had received a signal only 32 minutes ago, already decoded, which read that German torpedo boats were ordered to destroy landing ships off Port en Bessin and Grandchamp. The phone went dead again. He did not allow himself to sleep until lunchtime on 6th June, 24 hours at the desk. Harry’s war had been won. Harry was knighted in 1985 and died of lung cancer in 1998.


The Shark net had been broken every single day since 12 September 1943 as had the Dolphin net. It was not until May 1945, at the end of the war, that the Germans introduced a system that used more than one initial wheel setting; too little too late. Bletchley Park was sure that they could have reconstructed the bigram tables, or captured more, but the Germans surrendered before it was necessary, yet again, throwing luck in the direction of the British code breakers of Bletchley Park.

Reading about all those “lucky” incidents, incorrect assumptions and deception would make a religious person believe that “a god” was very definitely on our side in WW2, misdirecting the Germans into making mistakes, and covering any blunders made from the Allies side. Even the words of a traitor within the US Navy Department failed to convince the Germans that we could read Enigma. And the words of a captured agent should have set alarm bells ringing in German High Command, and again, nothing happened. To tell the Germans that the Poles had been in possession of Enigma for a whole 10 years before the war even started should have told the Germans that others too were more than likely to have been in on it, nothing happened. The Poles who had been hidden in a Chateau with all their work, escaped with only hours to spare as Germans arrived and took it over.

For those of you who wish to know, and possibly understand, the technical details of how everything worked I thoroughly recommend the book Enigma The Battle For The Code written by Hugh Sebag - Montefiore published by Phoenix first published 2000 and read the Notes at the rear of the book.

Appx 1 covers the Polish Code breaking Techniques.

Appx 2 – The Bombe.

Appx 3 -  Naval Enigma.

Appx 4 – Cillis.

Appx 5 – Rodding.

Appx 6 – Naval Enigma Offizier, how it was broken.

Notes abound disclosing masses of detailed information.

I have just purchased this (March 2016)
Next: How Enigma worked

Although linked from this page, I have used material from only one or two these sites: my thanks to Darek for this link