The Japanese attack on Pearl Harbor sparked a flurry of questions, the most obvious being “How could it have happened?” Despite a worldwide intelligence and surveillance network and a meticulously trained home guard, the United States could not prevent Japan from sneaking up and delivering a devastating blow. In the years following the attack, eight major investigations would attempt to answer the question of how it had happened.

The first investigation was a closed-door board of inquiry ordered by President Roosevelt eleven days after the attack. The Roberts Commission, named after its chairman, Supreme Court Justice Owen Roberts, concluded its investigation January 23, 1942, by laying the blame on Admiral Husband Kimmel, commander in chief of the U.S. Pacific Fleet, and Lieutenant General Walter C. Short, commanding officer of the U.S. Army's Hawaiian Department. In its official report, the Roberts Commission declared that the two men had failed to exhibit the qualities of high command. Kimmel and Short had been relieved of duty by the time the commission concluded its investigation, and both men soon retired.

Six more closed-door investigations were conducted by the U.S. Army or Navy over the next few years, their results cloaked in secrecy because of concerns over military security. It wasn't until after the war that the public would learn exactly what had happened on December 7, 1941.

Congressional Investigations

November 15, 1945, saw the beginning of a joint congressional investigation into the disaster. It lasted six months and produced more than 15,000 pages of testimony. Both the majority and minority reports issued at the end of the investigation placed the primary blame on Kimmel and Short, noting that the two men had failed to heed warnings from Washington of a potential enemy attack and that they had failed to properly alert their forces. The committee concluded that while Kimmel and Short had made “errors in judgment,” they were not guilty of “dereliction of duty.”

The congressional committee's report was not the end of the debate. Many questions remained, but the documents that might answer them would not be declassified for many years.

Why Warnings from Washington Were Not Heeded

As for war warnings from Washington, they were received and acted on, but ineffectively. Kimmel received a dispatch from the Navy Department warning of anticipated aggression by Japan, and Short received a similar warning from the War Department. Kimmel decided not to raise the alert status of the navy forces he commanded because he didn't want to frighten Pearl Harbor's civilian population. He did, however, send two aircraft carriers with escorts to deliver planes to Wake Island and Midway, an action that accidentally helped save the valued ships when the Japanese finally attacked.

Short, who was in charge of Pearl Harbor's defenses, reacted to the warnings from Washington by bolstering precautions against sabotage, considered the main threat because of the island's large Japanese American population. To that end, he followed military policy and ordered all the warplanes parked wingtip to wingtip so they would be easier to guard. Sadly, the plan only made them a more convenient target for Japanese bombers.

Kimmel and Short were also hobbled in their defense by the fact that they were denied access to intelligence reports based on the decoding of Japan's communiqués to its diplomats in the United States. Had they known what the intelligence community knew — but failed to share — they might have reacted differently.