Just wondering why there were so many different investigations and hearings, by many different authorities, after the Pearl Harbor disaster? Looks to me like there were nine, in total. Starting just after the attack and ending with The Joint Congressional Committee, in 1946. Just seems to me that if the first investigation, got to the bottem of the problem, another investigation wouldn't be needed. Same thing with the second investigation and so on. I am just wondering, by the ninth committee/inquiry/investigation/board/commission, if it didn't become obvious, that they weren't going to get the bottem of it. A number of the key players in all this, just didn't seem to cooperate and/or chose to kept there mouth shut. I'm sure many felt, that this was monday morning quaterbacking and there was a war to win. Finding blame, was not really going to change what happened. I'm just not sure any investigation, should have taken place during the war. After the war was over, I can see it, at least to some extent. By the time the war ended, warfare had changed so much, FDR had passed on and the whole world was totally different.
If you look at the sequence of the investigations you'll see the evolution of the process. They lay it out in "part 40" of the Congressional Investigations, the "summary volume". Short answer is that the Army and the Navy conducted investigations, then they were sent back to clarify certain things, and, after further review, a few more questions were asked. The 9th investigation, the Congressional Hearings, was the most exhaustive because they knew what questions had already been asked and what needed to be asked. The former investigations were included in the exhibits of the Pearl Harbor Attack Hearings. One interesting feature of the Hearings is the executive order to release the Magic intercepts.