alternatehistory.com

An idea I'm kicking around: what if during the invasion of Poland the Germans had discovered the full extent of the Polish analysis of the Enigma machines?

IOTL the Germans believed that breaking Enigma would be impractical, and were fairly careless about procedures. Discovering that the Poles could read their early machines and that with some effort the Allies would be able to read messages from the new (as of 1939) machines would be quite a shock.

The Germans will, naturally, take steps to improve their encrypt methods and procedures. This will greatly hamper (though not stop) Allied SigInt. With only minimal and erratic ULTRA intelligence, how is the war changed?
Top