[Poohbah]

IIRC, the Japanese investigated this incident thoroughly, and concluded that Yamamoto's itinerary was retransmitted not once, but several times, and that fairly low-grade codes were used on some versions. In other words, they convinced themselves that JN-25 was still secure.

An excellent discussion of the intelligence war in the Pacific Theater is John Prados' Combined Fleet Decoded, recently reprinted in trade paper by the US Naval Institute Press.

[hchutch]

I also recommend And I Was There, the memoirs of Edwin Layton. He gives a good account of the codebreaking efforts, and he also provides the best explanation for Pearl Harbor as well.

[Grampa Dave]

You guys are right on top of this.

HCHutch, we had the right people in the code cracking groups and in the OSS including its founder during those dangerous and early days of WWII and right before Pearl Harbor. There were a lot of unsung heroes from then to the end of the USSR.

I have never been a fan of FDR's, but he realized the importance of the secrecy that surrounded our code crackers and what they did. There is no evidence that he ever jeopardized any operations back then, and he helped guard the reality of what had been accomplished re the JN-25 and the Engigma breakthroughs. I'm sure that he learned from his friend Prime Minister Churchill who made some bad intel mistakes after WWI. Churchill was an absolute master of keeping these secrets really secret before and during WWII.

I doubt if history will say the same for Carter, Johnson and of course the Clintoon in protecting the secrets of our people cracking codes and working in secret to protect this country!