[cyberferret]

Like most, I always thought that the allies were desperate to get their hands on these machines during the war.

I was lucky enough to get to play with one of these things when a lecturer from the Bletchley Park foundation toured here some years back. She gave a fascinating and riveting talk on the history of the device.

I was surprised to hear that these were actually commercially available before the war, and that the allies had quite a few of them in store already. The crucial thing they were after were the booklets with the daily rotor and plugboard settings - far more valuable than the machines themselves.

[demallien]

Regardless, Enigma was pretty low-value intelligence. It would give you things like the daily position of u-boat packs, but generally speaking there isn't much you can do with this type of information - maybe increase the ability of your conveys to avoid U-boats, or increase slightly your ability to hunt them.

The real game was the Lorenz-stye encryptors that were used for communications between German commands. These delivered the strategic information about mid-to longterm movement of units and so on which allowed they Allies to correctly anticipate attacks. These were the messages that Colossus was used to decrypt, as opposed to the Bombes which were decrypting Enigma traffic, and which were largely derivative of earlier Polish efforts to decrypt Enigma.

I read a book a while back https://www.goodreads.com/book/show/1127838.Colossus that looks at all of this in detail. Surprisingly, if the book is correct, Turing seemed to have limited contact with the Colossus effort, and was more involved with the Enigma decryption. The Colossus people didn't seem to be terribly occupied by ideas such as Turing-completeness, they were just building machines that were capable of doing certain operations at high speed.

[SteveNuts]

I thought the commercially available models did not include the pegboard, which was crucial for the higher # of possibly combinations?

[cyberferret]

I think you are correct. Also, the Kriegsmarine version had an extra rotor, plus they also used a secondary code book to encode keywords before encrypting on the Enigma.

Those were, from what I hear, much harder to break, thus the efforts to capture the code books and devices from the U-boats.

[detaro]

If I remember right they also used different rotors (and added more of them to swap out over time), so that's another thing to capture.