Utilising ULTRA

I have been reading a couple of things lately which have led me to start thinking about how the information gleaned from Enigma and Lorenz decrypts was used. There is no end of stuff on the crypto-analytic side of things but I'm thinking here of how the information was organised. There are references to a card index but no explanation of how it worked. Was there one index or several? How were they indexed? Can anyone point me to a book or site which might cover this?
Unfortunately I do not have the book to hand but Station X is a good start.

The card index listed information so if Lt Smith was mentioned being posted to X unit as signals officer and later on his name came up as being in X town they could deduce that X unit had moved. It is about picking up very small bit of info and joining them together. It would appear that some net had very high levels of encryption and security and others very poor, but the same person, unit or activity could be mention in both. This would give clues to decoding the more secure signals. So a highly secure signal is sent to unit X and an hour later on the admin net they tell the depot to send all future kit to town Y from Z date. From the card index it is known that this depot provide AAA spares so unit X must be AAA. Get the idea.
Code Breakers The Inside Story of Bletchley Park edited by F. H. Hinsley and Alan Stripp gives a decent description of how the decrypts were organised and passed onto who ever needed them, but the technical details of the how the codes were decrypted is a bit too much for my tiny brain to handle.
This guy's work (written from the perspective of an information specialist rather than an intelligence officer) will probably answer any questions about GC&CS card indices in rather more detail than you want


A paper he gave last year is available on-line at


which may do the biz without you looking further


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