How did Churchill communicate with generals overseas?

[carnivorousplant]

I am still reading Churchill’s The Second World War. Volume three, The Grand Alliance.
How did Churchill secretly communicate with his generals overseas? For example, he tells General Wavel that tanks are being shipped to him in a fast convoy through the Mediterranean rather than around the horn, and urges him not to tell anyone that they are coming through the Med which will make their arrival much earlier than expected. The Allies will soon be reading Japanese and German codes. What method did Churchill use to ensure secrecy?

[griffin1977]

From 1943 onward SiGSALY was used by the US and UK.

[carnivorousplant]

We are still in 1941 here, Britain is going it alone, save for Greece I believe.

I didn’t think about he communicated with Roosevelt. From your link, and thanks!

“Before the full involvement of the United States in WWII, the United States and the United Kingdom were using transatlantic high-frequency radio for voice communications between senior leaders. The analog voice privacy system in use, called the “A-3,” provided reasonable protection against the casual eavesdropper, but it was vulnerable to anyone with sophisticated unscrambling capability. This system continued to be used during the early part of the war, and government officials were warned that they could be overheard. In fact, it was later discovered that a German station in the Netherlands was breaking out the conversations in real time. This situation was intolerable, but neither the U.S. nor the U.K. had a ready solution.”

[carnivorousplant]

I thought some ballsy British destroyer was running between Britain and New York with a diplomatic bag.

[DSYoungEsq]

@carnivorousplant

I thought some ballsy British destroyer was running between Britain and New York with a diplomatic bag.

Not owls?

[carnivorousplant]

@DSYoungEsq

Not owls?

I have no idea what the Ministry of Magic was doing in 1941. Perhaps they were making convoys carrying tanks invisible.

[Francis_Vaughan]

Despite the popular impression about the British having had a triumph in encryption breaking the German codes, this is more about the victor writing history. Churchill made an astounding blunder when he wrote the history of WW1. In it he described how the UK had broken the German codes, and how important that was. This was a key component in spurring the Germans adoption of much stronger encryption in WW2. The UK had not considered the problem at all, and were still using very dated technology. And the Germans were breaking their codes continuously. After WW2 the Allies were much more careful. Information about the breaking of the codes was kept secret for a long time, indeed, breaking of the Lorentz machine using the Collossi was kept secret for decades. The fact the the cold war was upon them had a part to play in this (although the Soviets knew all about it anyway.)

[Peter_Morris]

Churchill made an astounding blunder when he wrote the history of WW1. In it he described how the UK had broken the German codes, and how important that was. This was a key component in spurring the Germans adoption of much stronger encryption in WW2.

Cite that it was Churchill’s writings specifically that spurred them?

[carnivorousplant]

Code breaking in WWII was not written about in the book I am reading.

[GreenWyvern]

@Francis_Vaughan

Churchill made an astounding blunder when he wrote the history of WW1. In it he described how the UK had broken the German codes, and how important that was.

Are you perhaps thinking of this:

At the beginning of September, 1914, the German light cruiser Magdeburg was wrecked in the Baltic. The body of a drowned German under-officer was picked up by the Russians a few hours later, and clasped in his bosom by arms rigid in death, were the cypher and signal books of the German Navy and the minutely squared maps of the North Sea and Heligoland Bight. On September 6 the Russian Naval Attaché came to see me. He had received a message from Petrograd telling him what had happened, and that the Russian Admiralty with the aid of the cypher and signal books had been able to decode portions at least of the German naval messages. The Russians felt that as the leading naval Power, the British Admiralty ought to have these books and charts.

The codes were not broken.

They simply acquired the code books, which proved very useful. But when the German codes were changed, they lost the ability to decipher the signals.

This passage wasn’t of any use to the Germans, except to warn them to be more careful with code material.

[carnivorousplant]

Here is an interesting Wikipedia article about WWI codes.

[Francis_Vaughan]

@Peter_Morris

Cite that it was Churchill’s writings specifically that spurred them?

I’m going on memory here, so I would have to look it up, but I’m pretty sure one of my histories on the work at Bletchly Park made this assertion. Of course, that assertion itself would need backing up, and may well be open to some criticism. It gives me an excuse to pull the books out again, but I can’t promise anything.

[MEBuckner]

What about submarine cables for sending telegraphic messages? My understanding is that the British Empire had a big lead in that particular collection of technologies, with telegraph cables on the beds of the worlds oceans linking together the various parts of the Empire in a way that would make it very difficult for a foreign power to intercept. (See the All Red Line, for example.)

[carnivorousplant]

The British dragged up and tapped German cables in WWI. That is how they were able to notify the USA about the Zimmerman Telegram.