Today, I learned that if the Japanese military had been in the habit of reading the Chicago Tribune, WW II might've run a lot longer.
You see, in June 1942, a Trib reporter spilled the beans about the U. S. reading encrypted IJN radio traffic, thanks to a buddy who was XO on the USS Lexington. It's still unclear exactly how the Tribune's Stanley Johnston got the information from Commander Morton Seligman. Seligman, an otherwise exemplary officer who had been headed for great things, found his Naval career stopped cold; Johnston narrowly avoided being brought up on espionage charges and the whole thing was swept under the rug, in hopes the Japanese military wouldn't notice.
Given the complete lack of love between the Tribune's Colonel McCormick and President Roosevelt dating back long before the war, FDR probably regretted having to officially ignore the incident.
What do you know, Imperial Japan wasn't reading the Chicago papers. They never found out we were reading their mail, or at least a fair amount of it. They might not have believed it; feeling secure behind a difficult language for outsiders to learn and an encryption scheme that added complications to a mechanical system similar to Germany's Enigma, they apparently never considered any risk to their secure communications other than losing code books to the Allies.
To this day, the Tribune considers their report quite a wonderful scoop; but it could have delayed the war's end by a couple of years if Japan had realized we were reading over their shoulder the whole time.
Commander (on retirement, Captain) Seligman served ashore until 1944, and never uttered a word of complaint or explanation about it for the rest of his life.
6 months ago