D-Day and the role of Colossus

Seventy-five years on from D-Day, information is still coming to light to show the role of Colossus and the breaking of Lorenz, Hitler’s most secret cipher.
In Block H, the home of Colossus, Mark Priestley and Gavin Clarke reveal the pressures codebreakers worked under in the run-up to D-Day and the difficult choices they had to make in deciding what Lorenz messages to tackle. From their research at the National Archives, they also reveal some of those key pieces of intelligence that Colossus and the codebreakers were able to uncover and that gave the architects of D-Day the confidence to know that the enemy had swallowed the vast campaign of deception over the place, timing and scale of the Allied landings.
It is suggested that you watch the following video "Colossus at 75" to set the scene for the discussion that follows: • Colossus at 75 - Colos...
Recorded: 28th September 2019.

[@spooley1959]

Thank you for preparing and distributing the video of the D-Day talk. It was a great watch and particularly welcome to me as a relatively remote member (in Wiltshire). I look forward to the Apollo talk appearing in due course.

[@jabar2587]

Great lecture and very engaging. I learned so much about behind the scenes and the process of the message intercepts by all involved. Easy to understand and follow. Looking forward to watching more of these types of informative talks

[@rogergreenwood1536]

Fascinating bit of history, well presented. Along with Jellyfish, Bream, Stickleback, Mullet, Perch etc, I do wonder if an obscure network link was named Pike? (Don't tell him).

[@brucevilla]

Thanks for Uploading.

[@nicholasperry2380]

A very interesting talk and I hope Gavin's nerves have recovered since. If anybody knows Mark Priestley could they ask him when the break-in to the June 1944 messages took place? In addition to the Colossus2 myth there are several concerning Allied actions in the first few days such as the 3rd Division advancing tentatively towards Caen as enigma(?) warned German armoured forces were already deploying. It seems unlikely in view of the Q&A session but a date would certainly clear a lot of things up. Thank You.

[@thehaguefortnite_163]

The typewriter on the table had a foresight as well.... ...great talks thanks!

[@markrowland1366]

The low rate of casualties is truely indicative of the value of the investment Bletchley Park showed itself to be. The USA had withdrawn from that field, only hanging by it's fingertips, in the form of a husband and wife who's research and the training provided the leaders in intelligence and the cryptanalysis who were the core of the rebuilding which cracked the Japanese naval and diplomactic codes which helped avoid disaster in early 1943.

[@johndododoe1411]

I gather from the end of this lecture that we should not believe the story of Eisenhower at SHAEF set D-day from a fresh decrypt of a tunny message where Hitler reiterates that Normandy would be the decoy and Calais the real invasion.

[@cowdaddy4595]

That appears to be an Old Wives' Tale. Ike may not even have been aware that the code was broken, considering that the Brits were operating on a need to know basis.

[@jfbeam]

@@cowdaddy4595 Supposedly, the US had their own Colossus machines. So it's possible they had their own intercepts.

[@greggashgarian8360]

The second speaker needs to study the things he's not familiar with better. E.g. A Tiger's 88 can't shoot down planes.

[@deepdiver51]

Plus he needs to slow down…..

[@localbod]

In my experience, anyone who describes themselves as a nerd, is definitely not. Real nerds are just interested in their given subject matter and not what people think of them. Same old 'Tiger tank v Sherman tropes.

[@henryj.8528]

No, the folks at the Knockholt intercept station didn't "listen to a noise coming over the earphones." That's Enigma. Fish traffic was a radioteletype signal which was a 5 bit Baudot code transmitted by frequency shift keying. It was commonly used for news distribution by the 1930s (AP UPI, Reuters). At first Fish traffic was recorded with pen recorders on paper tape. The boring part was having people visually scan the paper tape and mark the letters the zig zags represented. But most radioteletype messages were first punched on paper tape and then transmitted to a receiver which also punched a paper tape. The Knockholt station recorded Fish transmissions using commercial radioteletype equipment. Nothing secret about that. The secrecy was all in the encryption. He also gets it wrong when he says, radio wasn't used in WWI. In fact, the first use of radio in battle was at Tsushima in 1905. By WWI it was commonplace. The weird part is when he suggests that the Germans would shift their frequency if they thought their signals were being intercepted. There's no way to know that and all militaries assume that their signals are being intercepted. The fact that anyone can intercept a radio signal is what makes encryption necessary. Also, there was no qualms about listening to German radio traffic. He mistakenly mixes up the old story about Secretary of State Simpson who in the 1930s remarked that "Gentlemen do not read each other's mail" when he shuttered the "Black Chamber," a State Dept. office that had successfully decoded German radio signals during the first World War. By the time the second World War came around, there were no such qualms. This lecture was not very well researched...

[@jfbeam]

If they thought someone was decoding their transmissions, they'd change the codes. Changing frequency would be useless; it would take a few seconds to find it again. (I guess they've never seen a modern day scanner? Or used an old analog AM/FM radio.)

[@localbod]

I agree. It sounded like utter rubbish to me that anyone from that side of the military would have any qualms about listening to the enemy's radio traffic. Also, the suggestion that radio as a medium for coded messages was relatively new by the second world war is incorrect.