While the cracking was announced in '73, I know that is was Winterbotham's book The Ultra Secret in 1974 that enabled the fact that Enigma had been cracked to become widely known. What I would like to know is what reaction there was from the German military, if any.
Follow up: less well-known is Britain's success in cracking German military codes in WWI with Room 40 (among other successes, Britain usually knew in advance whenever the High Seas Fleet was coming out to play). Prior to WWII, how aware was the German high command of Britain's cryptographic success in WWI, and what effect did this have on their security measures?
A previous thread with this question:
(Speculation: the introduction of self-posts rewarding karma may lead to duplicate questions in the future - not that this particular post is necessarily caused by that)