Kronos April 10, 2013 1:30 PM

I have found the battle of Midway to be one of the most interesting naval engagements of the past 200 years. At a recent family reunion another history buff told me of a shared relative who was an eyewitness to Midway as a gunner on a U.S.N. aircraft. Amazing how vital the crypto was to the outcome, especially against overwhelming odds.

Jonathan Wilson April 10, 2013 9:35 PM

One of the interesting things they did was to send a fake message in-the-clear about Midway knowing that when the Japanese picked it up, they would probably tell the commanders in the fleet (the one they were almost sure was on its way to Midway) about the message, allowing the code-breakers to confirm that Midway was in fact the target.

Clive Robinson April 11, 2013 3:39 AM

@ Jonathan Wilson,

One of the interesting things they did was to send a fake message in-the-clear… …allowing the code breakers to confirm that Midway was in fact the target.

I don’t know if this trick was thought up independently or not, but the British at the behest of Bletchly Park used to send out RAF aircraft to drop mines in entrances to important German harbors and docks. Knowing full well it would be seen and sent out as an “All vessels” warning using the weaker “Dockyard Cipher” as well as the stronger Kriegsmarine enigma for U-Boats. Thus giving them a known plain text to work with. Bletchly called the process “gardening” as hopefully they were “sowing the seeds that would alow them to reap the harvest”.

Clive Robinson April 11, 2013 4:13 AM

It should be mentioned for those that don’t know the Japanese cipher machines (given colour codenames like “purple” by the US Cryptographers) were entirely different to the German enigma system.

They were based on “half rotors” and “uni-selectors” as their base components. IIRC due to the complexities of Japanese they actually had a seperate rotor for the equivalent of vowels which actually made attacking them slightly easier.

These days we would probably regard the Japanese cipher machines as being marginally inferior to the German Enigma and British Typex. But that in now way diminishes the work the small team of US cryptographers put in to break the systems the Japanese used.

Also the US actually had seperate teams of cryptographers working independently of each other. One of the teams worked on German Enigma as the U-Boats had become a distinct problem in US coastal waters. Part of the problem was that the supposed “special relationship” was not working at the time and Churchill whilst trusting the US President and one or two key US staff at the time did not trust the US armed forces to properly follow the “Ultra Rules” and thus keep the breaking of Enigma secret. Part of this distrust was down to the fact that some British code breakers were detailed with actually receiving and breaking US Naval transmissions and thus it was assumed the Germans Likewise. This was based on the fact that the Germans were reading British Naval traffic was known at Bletchly (but for various reasons it was not acted upon in the way you might think).

The WWII battle of the signals is a fascinating subject, not just at the mechanical end of breaking and cataloging the intel but also at the higher levels. It has all the failings of bitter inter-departmental rivalries causing systemic failures but also games of bluff and double and triple bluff between not just the oposing sides but nations on the same side.

All in all it was amazing at just how these small teams actually did their jobs and have such major outcomes on the direction of the war despite the rivalries and chicanary of the more general service and government bureaucrat turf wars.

Needless to say that many if not most never saw the recognition they rightly deserved in their lifetimes, and it is only of more recent times that the debt we owe is finally comming out from under the shroud of secrecy.

Michael Hoffmann April 11, 2013 11:01 PM

This topic can’t leave me but with mixed feelings. Among my grandfather’s war stories, he told me about “his” Enigma and explained to me how it worked and how it was totally unbreakable.

He passed away before “Ultra” was declassified. I wonder what he would have said when he found out that in effect the Allies (and by extension the Soviets) were reading over his shoulder.

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