Knox's report caused FDR to order a commission, headed by Supreme Court Justice Owen Roberts, to carry out a more thorough look at the attack's circumstances.
The Roberts Commission report, issued in December, 1942, exonerated major political figures in Washington, and laid much of the blame for ill-preparedness on the top commanders on scene in Hawaii: Army General Walter Short and Admiral Husband Kimmel. Both were demoted, and both retired from the military within months.
Subsequent investigations began to spread blame for the debacle more widely. Six more probes were held during the war years, counting separate efforts from the Army and Navy, and associated spin-offs.
For instance, a Naval Board of Inquiry held in 1944 blamed Admiral Harold Stark, chief of naval operations at the time of Pearl Harbor, for not adequately advising Kimmel of the critical situation between the US and Japan in the weeks prior to the attack.
Wartime secrecy needed
All these investigations were hampered in some manner by the need to maintain wartime secrecy, particularly in regards to US code-breaking efforts.