German code breaking during WW2, Part Three

well_chuffed, Going Postal
A Slidex, bearing a date 12/43, with one vocabulary card and code strips in place, and two more different cards

How successful were the Germans with the Signals Intelligence during WW2 and even just before.

We have grown used to the astounding success of Ultra and possibly associate success with breaking an almost unbreakable code and then using its fruits to further our war aims. These aims included the very significant “don’t let the other side know we can do this”.

This is not the only way to be successful. There can be betrayal of codes , capturing of code books and machines , traffic analysis , deciphering of not so difficult codes all the way up to breaking high level machine generated codes. Later on there was also radar detection and disruption.

The Germans never achieved anything on the technical level of Ultra but they did realise an awful lot of information from Signals Intelligence and had some major successes when using the knowledge.

well_chuffed, Going Postal
The M-209

As was said by one of the German PoWs , when you are winning and advancing fast , the Signals Intelligence is of little use. On the other hand when you are bogged down or retreating it is like gold.

As we have all read , Ultra intelligence could never be used unless there was a plausible other explanation as to how we had acquired the information. The other side was never to know that Bletchley Park had cracked the code. It has to be assumed that at least some of the German side had decided the same but obviously not all of them.

In terms of the number of codes/cyphers successfully read , the Foreign Office has to be the winner. They cracked much of what they looked at , before the war especially they were very helpful to the little man as he set about expanding his realm by bluster rather than outright war , telling him exactly how far he could go without being attacked.

In the TICOM report at the end of Volume 1 , there is a table of countries , their codes and whether the Germans could read the transmissions. They targeted over 50 countries , this was mostly done by the Foreign Office , the Military side were more involved with who they were fighting at any time or who they were likely to be fighting. One of the more obvious omissions before 1941 was the USA , it seems to military did not know they were going to be the enemy adding more confusion to Adolf’s declaration of war on the USA. Possibly one of his biggest mistakes.

As a backdrop to the Spanish Civil War , they did not have much success with the Spanish Government codes but they read all of the Spanish Republican codes. It wasn’t just bombing defenceless villages where they honed their skills.

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When it came to the Anschluss with Austria , they did not really need to worry about the Austrians but they were very interested in the anticipated French and British reactions to the annexation.

The Luftwaffe was reading most of the Czech traffic , this being helpful when the Army moved into Sudetenland and later took over Bohemia and Moravia. Adolf was in Prague  the day after it was captured and he would not be tempted to risk his own neck.

Then came the war. Hitler’s opinion was that the west would not go to war for Poland. There is no indication in the document that his Signals Intelligence supported that view but he was very much mistaken.

The most penetrated military part of the British was the Royal Navy. The broken codes were
Combined Assault Code
Administrative Code
Naval Code Number 2 until 1943
Naval Cipher Number 3 until 1943
Naval Cipher Number 4 until 1943
Fleet Code from 1944 to 1945
Some of these codes were Coastal Command and Coastal Defences , probably not so useful in the longer term but Operation Cerberus , the escapade of the Scharnhorst , Gneisenau and Prinz Eugen racing up the English Channel from Brest to Norway was carried out using intelligence on the whereabouts of the British warships. Although it came under air attack , which the Luftwaffe opposed , no Royal Navy ships seemed to get anywhere near them.

The RAF was also broken into
Air Force Code and Bomber Code were broken
They also had a captured cipher device that was useful to them until 1942

The Army fared little better
Tiger Code , War Office Code and SLIDEX were broken , LINEX stayed secure and TYPEX was not broken even though they captured machines at Dunkirk , Brest and in North Africa.

As was mentioned before , the Atlantic convoys were being hammered while the Germans could read the signal traffic.

The Luftwaffe were experts in traffic analysis , this did not require codes to be broken , the analysis was of what units were where and what they were generally up to. This allowed for example , the Germans to know where bomber raids were heading to by analysing the fighter escort’s progress rather than the bombers making their feints and course changes. They could even work out where the dummy raids were going and ignore them. What they did not work out was how vital our Chain Home radar sytem was during the Battle of Britain , they scarcely attacked it. , has they done so we would probably have lost.

The Germans also jammed radar and radio signals but not where the signals were giving them intelligence they needed. Again , no sign of anyone on our side putting two and two together. There was also an instance where Goering was visiting one of the intercept units and was invited by one of the operators to listen in. He spent half an hour listening to the chatter , remember he had been a fighter pilot , and was absolutely amazed at the amount and type of chat that was being picked up.

The Dieppe raid was also compromised during execution if not before because the signals were being read and in real time during the raid. No wonder it was carnage. There have been several theories that it was betrayed , perhaps it was but they had enough Intelligence from the signals to sink it anyway.

well_chuffed, Going Postal
The Typex 23, pictured, was similar to the Mark 22, but modified for use with the Combined Cypher Machine (CCM)

In North Africa , the Germans were reading much of the British traffic and during the siege of Tobruk all communications from Tobruk were being read. Whatever they tried the Germans knew beforehand what was going on.

As far as the US military was concerned , the Germans paid them no attention until 1941 and had a bit of catching up to do. They had been monitoring their aircraft movements across the Atlantic but not much else. There was some success against the lower level of machine created signals , the M-209 for instance , and the manually produced codes but the Americans had their “big machine” , the SIGABA , and that was never cracked.

On the eastern front the Luftwaffe were also skilled at using traffic analysis and the Army was breaking into some of the codes the Russian Army was using. The one time pads were the most secure method used and they were never broken into.

Looking at the signals that were broken it seems certain that the Germans to some degree also adopted the approach that we used with Ultra. Don’t let the enemy know we can read the codes or they will change them and blind us. Anything we do must explained by other means. With the amount of codes that had been compromised it seems rather strange that Adolf did not know that D-Day was going to be in Normandy. Did the little Austrian really decide to annihilate his nation because he had failed in his dream of a thousand year Reich?

© well_chuffed 2018