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Germans broke British naval codes in 1941

• Message 1. 

  Posted by Erik Lindsay (U231970) on Sunday, 17th February 2008

  Apparently a German U-boat captain obtained the naval code book from a sinking British freighter off Norway and gave it to B-Dienst right away. As I understand it, Bletchley Park spotted this within a month or two and promptly warned the Admiralty that the German U-boat fleet had access to British naval codes. For some reason, the Admiralty did nothing about that for nearly a year. The loss of hundreds of ships and thousands of lives can therefore be laid at the dragging feet of the British Admiralty.
  
  Why was nothing done to change the codes? Who was responsible for this criminal neglect and was anyone ever held accountable?

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• Message 2

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  Posted by peteratwar (U10629558) on Monday, 18th February 2008

  Any sources for this?
  
  Seems unlikely a freighter would have had any of the more secret codes.

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• Message 3

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  Posted by Backtothedarkplace (U2955180) on Monday, 18th February 2008

  Hi peter@war.
  
  All merchant ships carried copies of the convoy codes and I think some of the lower naval codes.
  
  So its pretty much correct. As to whay there was a delay. probably due to the fact that they needed to protect enigma. A sudden change in codes after it had been broadcast in a supposedly secure code and you might as well tell the germans yuo can read their signals. The delay is probably down to them waiting for it to be "discovered" by an alternative and less important source. or to replicate the actions of a slow discovery that the codes have been cracked.
  
  Not nice if you were on one of the ships sunk as a result. But given the effects that enigma is supposed to have had on allied planning probably one worth taking.

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• Message 4

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  Posted by Erik Lindsay (U231970) on Monday, 18th February 2008

  I don't follow your logic, backtothedarkplace. What does protecting enigma have to do with the information that the Germans have broken the British naval code? Enigma was the German code, and B-dienst was convinced that it was impenetrable. They had no reason to believe otherwise if the British were suddenly to change their naval code.
  
  Considering how dependent Britain was on imports for survival, delaying a change in the RN naval codes for nearly a year when the Admiralty KNEW that the Germans had broken the current code was downright criminal.
  
  I suspect (this is just my personal opinion) that the Lords of the Admiralty didn't trust their own code breakers and/or felt that using such sneaky tricks to fight a war was ''unsporting''...''not cricket, doncha know?'' so they ignored the information.
  
  If any of you have other opinions or know the real score please, have at it.

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• Message 5

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  Posted by Backtothedarkplace (U2955180) on Monday, 18th February 2008

  Hi Erik.
  
  lets see if I can explain my self better.
  
  The UK knows its codes are broken because it is reading enigma.
  
  Any action we take compromises the security of that fact.
  
  Enigma is the goose that lays the golden eggs. While the codes captured by the Germans are important. even running the risk of possibly revealing that Enigma has been broken is out of the question. Enigma is giving much much more than simple tactical information and remember if the German navy twigs its broken the whole German armed forces is going to change code machines. The window into the German plans closes.
  
  So you have to wait. Until either the capture of a German ship gives you the information or a spy feeds it to you. or the germans get careless and broad cast it in clear. or an escaped prisoner reveals it.
  
  Only once there is a reason that you know the germans will buy can you change your codes.
  
  Part of the problem with Enigma or for that matter any signal intelligence. is the fact that any action you take using info you have received jepordises your source. You can re route the vital convoys. But you cannot protect every single convoy using it. If there are too many lucky british escapes the Germans will get suspicious which the U boat command did at least twice. once they upgraded the ir system by adding new rotors to the machine and once they reviewed it and once an admin review decided it was safe to carry on using it. If the allies had been less careful in using it then a third review might have decided to either add another level of encryption. Or change the whole system even if it was just to be on the safe side.
  
  Did the descision taken cost lives? Probably. Were ships sunk that neednt have been? Probably.
  
  But look at what the Germans got up to in the periods where we couldnt break Enigma. Imagine the happy times lasting for ever?
  
  

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• Message 6

  , in reply to message 5.

  Posted by SONICBOOMER (U3688838) on Monday, 18th February 2008

  Apart from anything else, by 1944 the U-Boats were an largely beaten force.
  There would have been no D-Day, or the build up to it, if this had not been the case.

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• Message 7

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  Posted by Triceratops (U3420301) on Monday, 18th February 2008

  There was the sorry tale of the SS Automedon captured and sunk by the German Raider Atlantis.
  
  Amongst the confidential papers captured,were the assessment of Japanese intentions and the admission that Britain would not go to war to protect French Indo-China and plans and deployments for Commonwealth forces in Malaya and Singapore.
  
  The importance of these documents to the Japanese war effort can be surmised from the fact that Japan only presented three ceremonial Samurai swords to German nationals in WW2. One to Hermann Goering, one to Erwin Rommel and the other to Bernard Rogge, captain of the Atlantis.
  
  
  
  
  Trike.

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• Message 8

  , in reply to message 5.

  Posted by Erik Lindsay (U231970) on Friday, 22nd February 2008

  <quote userid=</quote>Hi Erik.
  
  lets see if I can explain my self better.
  
  The UK knows its codes are broken because it is reading enigma.
  
  Any action we take compromises the security of that fact. </quote>
  I disagree, bttdp. I realize that Bletchley Park was aware that the RN code was broken because they read it on a German transmission… but when convoy after convoy is precisely intercepted, I don’t think the German’s would be suspicious if the RN suddenly changed its convoy codes. It might be considered a simple precaution or it may be attributed to a feeling on the part of convoy planners that such constant and accurate interception of their ships was more than a coincidence.
  BDienst was so sure that Enigma was impenetrable that I doubt if a change in the convoy codes 3 or 4 months after German intelligence broke the codes would have raised any eyebrows. For those reasons alone, I feel that your argument doesn't hold water. But there are other, more solid reasons.
  
  
  Reflect: After enigma was first broken, convoys were re-routed to skirt the wolfpacks, but the RN didn’t hesitate to use the info then. That strikes me as something far more likely to tell the Germans that their code had been broken than merely changing our convoy codes. German intelligence knew that something was wrong when all those allied ships ‘’just happened’’ to be directed away from the waiting wolfpacks time and time again, but neither they nor Doenitz ever believed enigma had been broken. He added extra rotors to the machines as a precaution since it couldn’t do any harm, but he was certain, right up to the end of the war, that the information about wolfpack movements was being leaked by spies in the dock areas or by someone in his own organisation.
  
  So I repeat...why didn't the Admiralty inform the people who had to handle the convoys and those who scheduled them, as well as the cryptographers of the RN that their codes had been broken?
  
  (And I still don't understand your reference to Poland)

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• Message 9

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  Posted by Backtothedarkplace (U2955180) on Friday, 22nd February 2008

  Hi Erik,
  
  Poland? I havent mentioned Poland. Have I?
  
  I'd still stick with the need to protect Enigma I'm afraid. To suddenly insist that a code is changed without being able to explain why? Just isnt going to happen now let alone during the war. Then theres the code itself. A book code I think? Means Inventing securely printing and circulating a whole new set of code books which is expensive and complicated to organise because to minimise leakage you are going to have to simultainously change on every single boat in the world at sea or not. That will take some organisation.
  
  The other option is that they just didnt care. which I dont belive.
  
  

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• Message 10

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  Posted by stalteriisok (U3212540) on Friday, 22nd February 2008

  hi dan
  
  very good posts and i am with you there !!
  
  certain things were known - but had to be ignored because of the bigger picture - which we now know about
  
  Crete - we knew when where and how - but we could only half use it because it was so obvious - the U boat war was won because enigma gave the details and pretended it was because of allied technology
  
  crete was lost but the battle of the atlantic was won because of enigma
  
  st

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• Message 11

  , in reply to message 10.

  Posted by Anglo-Norman (U1965016) on Friday, 22nd February 2008

  Fri, 22 Feb 2008 23:20 GMT, in reply to stalteriisok in message 10
  
  I believe that the value of Enigma intelligence is overrated. By the time much of it was decoded the situation had changed. The Battle of the Atlantic was won by improved technology, tactics and - perhaps most importantly - air power, against which U-boats had little protection.

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• Message 12

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  Posted by George1507 (U2607963) on Saturday, 23rd February 2008

  Most of this thread is baffling me. If the British code books were captured I can't imagine any reason why the codes weren't changed. It's possible that the British didn't know, that would seem to be the most likely explanation. If they did know then I can't see how acting on it would compromise the fact that they were decrypting enigma. If the Germans had wondered how the British were aware of it, I would have thought that they would suspect that the British knew about the ship being captured rather than enigma being cracked. Indeed the Germans were reluctant to believe that enigma could be cracked. There was a fair amount of evidence but they ignored it.
  
  However, having access to the code books is not the same as being able to decrypt messages. Bletchley Park could not decrypt messages at will - indeed most messages were not decrypted for weeks or even months, and many have never been decrypted. Breaking the code required slips from the enigma operators to give them clues about the wheel settings.

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• Message 13

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  Posted by Erik Lindsay (U231970) on Saturday, 23rd February 2008

  Hi George:
  
  I agree in general with your observations. I think the most telling point in the argument against British intelligence fearing the Germans would realize their code had been broken is the fact that when it was, convoys were routed away from the waiting wolfpacks. If the Germans didn't figure out their codes had been cracked by those actions, changing the British code certainly wouldn't alert them.
  
  As to the Admiralty being aware that our convoy codes had been broken, it's a matter of record. Bletchley knew that the Germans were reading our codes about 3 months after they began doing so, and promptly told the Admiralty. Admiralty, for some reason, sat on that information for at least 10 more months while our convoys were being attacked and butchered by U-boats waiting right across their routes. Thousands of tons of supplies and equipment along with the lives of the merchant seamen were lost because of their stubborn (or criminal) neglect.
  
  I brought this up because I was hoping someone might know why Admiralty failed to act on the info sooner than they did or if anyone had been held accountable for what, IMO, was an unforgivable failure.
  
  So far, no one has.

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• Message 14

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  Posted by stalteriisok (U3212540) on Saturday, 23rd February 2008

  hi anglo
  not sure if you are correct there
  
  in the late 70s there was a series "the secret war" detailing how sneaky beaky things had helped us win
  
  there was one episode about how we won the u boat war which said the same as you - technology, radar, longe range planes, beaufighters (?) with ring radar scanners etc
  
  when finally the truth about ultra was revealed, they remade this episode and showed how ultra had actually won it
  
  it showed that we knew exactly where the u boats were - and when they were meeting the mother ships for resupply - thats when we hit them
  
  but they had to pretend technology did it (ie carrot soup lol)
  
  st
  
  

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• Message 15

  , in reply to message 1.

  Posted by lindavid (U10745308) on Saturday, 23rd February 2008

  I have not heard about this story of the Germans reading RN codes.
  However I can say that Ultra was kept secret and only when a recce had sighted and been seen by them were Ultra intel used, this to protect the secret.
  Crete was defended and could have been but if the reinforcements had been sent this would have tipped off the Germans that codes were broken, thus Crete was only token defended to protect ultra.
  The series The World At War was made prior to ultra being released in the late 70s which may have changed this programme.
  
  Winston said "whatever the cost" perhaps the convoys were one of the costs.
  

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• Message 16

  , in reply to message 14.

  Posted by Anglo-Norman (U1965016) on Saturday, 23rd February 2008

  Sat, 23 Feb 2008 21:35 GMT, in reply to stalteriisok in message 14
  
  Well, I got that theory from a lecturer from a specialist during my history degree in 2003/4 (and have since heard it elsewhere). Of course, that doesn't make it correct, but at least it shows it's still worthy of consideration in rlevant academic circles (as is the Ultra won the war theory).
  
  I think I'll ask the folks at uboat.net - see what they make of it.

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• Message 17

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  Posted by MB (U177470) on Sunday, 24th February 2008

  It is not necessarily a case of people not trusting the code-breakers. Most were unaware of the full scale of the operation and the information was heavily filtered before being passed on.
  
  According to the Bletchley Park War Diaries, soon after the U-Boat messages became readable again in December 1942 BP realised that the Germans were reading Admiralty Cypher No.3 which B-Dienst had started doing in February 1942. By the end of 1942 B-Dienst were reading as much as 80% of this code but only about 10% of the decrypts were made in time to be used by U-Boats. But this enabled them to reconstruct the convoy timetables.
  
  Once it was realised the Germans were reading convoy routing and rerouting instructions (as well as the New York Harbour Master communications giving details of departing convoys) the use of Cypher No.3 was restricted but it took time to prepare new code books. Naval Cypher No.5 came into effect on 10th June 1943 and was never broken by the Germans.
  
  In 1941 BP had been reading the German naval traffic regularly.
  
  One 23rd September a signal was received confirming that three U-Boats were meeting so the Admiralty "rashly risked the secret of source of the information" and a British submarine was sent to intercept them. It did not sink them but collided with one. Donitz wrote in his diary on 28th September "the most likely explanation is that our cypher has been compromised".
  
  MB

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• Message 18

  , in reply to message 15.

  Posted by Anglo-Norman (U1965016) on Sunday, 24th February 2008

  Sun, 24 Feb 2008 12:22 GMT, in reply to lindavid in message 15
  
  Winston said "whatever the cost" perhaps the convoys were one of the costs. 
  
  Possibly. Winnie could be harsh. On hearing that the Channel Islanders were starving, and that the Germans had approached the British Government to provide aid for them, Churchill's response was "Let 'em starve!" He believed that The Germans would nab the aid for themselves, and felt it was better to starve the Germans out.
  
  In fact he was wrong - when the Germans did eventually get aid, from the Red Cross, they ensured it all went to the Islanders.

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• Message 19

  , in reply to message 18.

  Posted by Anglo-Norman (U1965016) on Monday, 25th February 2008

  Mon, 25 Feb 2008 10:21 GMT, in reply to Anglo-Norman in message 18
  
  Re: the importance of Ultra. I had a word with the folks at uboat.net, and their opinion - as I should have guessed - fell somewhere between the two shades of opinion here!
  
  In short, a lot of Ultra was useless, but a lot was important. However, none of it was any use without the technology and tactics to act upon it - and vice versa.
  
  At the same time, Ultra was only one aspect of SIGINT, which gathered together all manner of information. Unfortunately, as aspects of SIGINT analysis are still in use they remain classified, so it is impossible to get a clear understanding of the importance of the various aspects.
  
  Ultimately Ultra must be taken in context as part of a complex network of anti-sub measures - take away any one aspect, and the whole thing could collapse.

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• Message 20

  , in reply to message 19.

  Posted by MB (U177470) on Monday, 25th February 2008

  One of the advantages of the British intelligence operation was that even though much might be useless tactically they could analyse it and get useful information. Some of the trivial messages were also helpful in breaking into cyphers because they tended to be repetitive so predictable.
  
  MB

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