[infowarrior]

The code most penetrated was the diplomatic code, not the naval code...

Sorry, both the diplomatic codes (purple) and the naval (JN-25) were totally compromised to the US. Our interception of Japanese naval traffic, in compromised Japanese naval code resulted in some telling achievements, such as the victory at Midway, and the (and it cannot be put otherwise) assassination of Admiral of the Combined Japanese Fleet Isoruku Yamamoto. Both these happened well before 1945, or even 1944 for that matter (Midway was in 1942, and the assassination in 1943, I believe...)

the infowarrior

[GATOR NAVY]

I'm still pretty sure by Dec 1941, the code most penetrated was purple. You're right, JN-25 was being read at this point, but not the extent purple was. And all I've read said the Japanese transmitted by radio nothing of their plans for Pearl Harbor except the execute signal. Everything else was hand carried or telephoned to those who needed to know, which means even if we were reading 100% of their transmitted traffic, there would have nothing for us to intercept in the first place.