Western Front 1940 Radio Usage

[Alex Zetsu]

The French doctrine did not make large usage of radios during the 1940s. A lot of communication was done by motorcycle riders and signal flags. Some of this was due to the lack of radios, but pre-war planning actually emphasized minimizing usage of radios even among units equipped with them. They were not explicitly ordered to go to radio silence, but they were told that unless a message needed to be really urgent, it was best delivered by other means to avoid the possibility of message interception. This also meant radios for vehicles was not procured in significant quantities because if you aren't going to send messages, you don't need a lot of them.

During the war, this proved to be the downfall of the French in 1940. All parties in the war form the Germans to the Soviets to the British would make extensive use of adutio orders over radios to coordinate their units.

However, I'm a bit puzzled as to why the French were wrong. Encryption was possible, but not for a radio that could fit in a vehicle communicating voice orders. So a divisional commander might send his orders to his units, but they could not be encrypted the same way text could. So in 1940, the French were busy communicating through a mixture of old and new methods while the German divisional commanders constantly used orders that could be intercepted. The Panzers had radios to receive and transmit orders, but these were "plain voice." (as opposed to plain text) The few French radio operators could listen to all these delicious information being sent (not much else to do when you're ordered not to use your radio much) and know what the Germans were doing. Why wasn't this the key to French victory?

 

[Catspoke]

Language difference, plus many of the orders are mundane stuff, fuel trucks to here, kind of thing, or you don't have the ability to react on your side quick enough, I bet alot of the messages are like "advance with me " vs messages like 6 hours from now we attack the ridge"

 

[Karelian]

All German intercept units were thoroughly familiar with the French system as a result of the many field messages which had been copied during the Phoney War. The intercept units of Army' Group B were also familiar with the Belgian, Dutch, and British systems. December 1939 the Germans broke a special cryptographic system used by the French command in radio messages to the armies and military district headquarters. It had been used contrary to regulations prior to the opening of hostilities in September 1939. The Germans were able to solve this system because the radio station guilty of the violation was reprimanded and thereupon repeated the same messages in the proper system.

The Germans could identify the probable concentration areas of the French and British armies from the practice messages sent by the field radio stations, although the boundaries of army groups, armies, corps and divisions could not be established with any certainty.

By 10th of May French radio traffic in the Poperinghe - Ypres - Courtrai area, and British traffic in the Ghent area, enabled the German HQ to realize that elements of the French Seventh Army had advanced into Belgian territory. As early as 12th May a message from the headquarters station of the French Seventh Army was decrypted, indicating that the latter intended to defend the Dyle (River) positions.

Unusually long encrypted messages -- that the Germans were unable to break -- from French First Army headquarters to an unidentified higher staff located south of the Somme suggested that joint action or breakout attempts were being agreed on by radio. These breakout attempts then actually took place near Valenciennes, Arras, and Cambrai. Clear-text messages sent on 24 May, in which complaints were voiced about the lack or ammunition, rations, and fuel, confirmed to the Germans that the situation within the pocket was becoming critical.

Generally speaking, the Entente units transmitted too many messages and thus enabled the Germans to intercept them with out any trouble. However, except for serious violations of radio security, such as the sending of messages in the clear, German intelligence was far from omnipotent, because the majority of the Entente cryptographic systems proved unbreakable.

The French formations also had different performances: The 9th Army observed strict radio signal protocols and discipline.
Source:

https://www.nsa.gov/Portals/70/documents/news-features/declassified-documents/friedman-documents/publications/FOLDER_240/41748999078819.pdf

 

[Carl Schwamberger]

... However, I'm a bit puzzled as to why the French were wrong. Encryption was possible, but not for a radio that could fit in a vehicle communicating voice orders. So a divisional commander might send his orders to his units, but they could not be encrypted the same way text could. So in 1940, the French were busy communicating through a mixture of old and new methods while the German divisional commanders constantly used orders that could be intercepted. The Panzers had radios to receive and transmit orders, but these were "plain voice." (as opposed to plain text) The few French radio operators could listen to all these delicious information being sent (not much else to do when you're ordered not to use your radio much) and know what the Germans were doing. Why wasn't this the key to French victory?

There is some evidence the French did, but first what Karelian said. Much radio messages are to perishable to be of immediate use. A long term collection can serve analysts is studying enemy methods, but in the moment some are useful most are not.

I've often wondered if it were mere coincidence Guderians corps HQ was bombed by French aircraft around noon on 12th May. His advance CP, and his primary HQ had been hopping across the Ardennes for two and a half days spewing out a stream of distinctive signals. Even being all encrypted it would not have taken a competent signals analyst long to ID this as a important operational HQ transmitters.

Theres also the matter of the Germans using telephone wire whenever practical. When Guderian masked the movement of his forward CP circa 16 May it was done with a considerable length of telephone wire. That 12km+ length of wire was not on the trucks as a afterthought. The signals unit was prepared to run telephone connections whenever appropriate.

 

[Alex Zetsu]

There is some evidence the French did, but first what Karelian said. Much radio messages are to perishable to be of immediate use. A long term collection can serve analysts is studying enemy methods, but in the moment some are useful most are not.

I've often wondered if it were mere coincidence Guderians corps HQ was bombed by French aircraft around noon on 12th May. His advance CP, and his primary HQ had been hopping across the Ardennes for two and a half days spewing out a stream of distinctive signals. Even being all encrypted it would not have taken a competent signals analyst long to ID this as a important operational HQ transmitters.

Theres also the matter of the Germans using telephone wire whenever practical. When Guderian masked the movement of his forward CP circa 16 May it was done with a considerable length of telephone wire. That 12km+ length of wire was not on the trucks as a afterthought. The signals unit was prepared to run telephone connections whenever appropriate.

While Karelian brought some light on situation, it is rather comical. Much of the French communication was done with motorcycles. Some details are here, but most of the information is about Gamelin not the communications situation http://www.taylorfrancis.com/books/e/9781351126625/chapters/10.4324/9781351126625-1 But they gave out just enough information to have a leak. So while they suffered from a information lag where commanders in the backline are getting an outdated picture since most of their communications were old fashioned, they had enough of a leak to give the Germans information. I think they might have been better served with radio silence orders instead of getting the worst of both worlds.

While the Germans made use of telephone when practical, most communications from divisional commanders to brigade commanders orders were done in unencrypted radio signals. They signals units have a similar problem with much of the German logistics, a lot of stuff being bottlenecked in the Ardennes. Guderian just barely got his wire. And orders done to panzer platoons had to be done unencrypted. I won't dispute the German usage of secure communications when they could or that the French did use radio both of encrypted messages and plain text.

It is true that the volume of unencrypted messages was much higher on the German side, even division commanders were resorting to them at times.

 

[Karelian]

And to add insult to injury the French military intelligence did provide a lot of good information about the German intentions - but after they alarmed the French High Command of the early invasion dates that the Germans themselves called off, Gamelin became convinced that they were crying wolf, and disregarded their correct predictions that the Germans would attack through Ardennes.

After that the secrecy of tactical radio usage was of secondary value, because the German Hail Mary-strategic risk had paid off, and they had managed to achieve an operational surprise. Their air superiourity also enabled the Germans to mask their tactical movements during critical times of the campaign, even though the French did what they could with ground recon and raids. Martin S. Alexander has good articles about this aspect of the war.