Did Roosevelt Know About Pearl Harbor in Advance?
A persistent theory says President Franklin Roosevelt knew Japan would attack Pearl Harbor and let it happen to bring the U.S. into World War II. U.S. codebreakers were reading Japan's diplomatic messages, but the National Security Agency says those decrypts did not reveal what the Japanese military was planning. Eight inquiries assigned blame for unpreparedness. None of the findings the NSA summarizes says the attack was knowingly allowed.
Verdict: Unproven. The sources below do not establish this claim. That is not the same as proving it false. How we rate stories
The Story
On 7 December 1941 Japanese naval aircraft struck the U.S. Pacific Fleet and Army in Hawaii. According to the National Security Agency's history, 'In a little over 2 hours, 18 warships--including 8 battleships--and over 160 aircraft were knocked out of action.'
How could it happen? One answer that has never gone away is that it was allowed to happen. American codebreakers had been reading Japan's most sensitive diplomatic messages since mid-1940, under the cover name MAGIC, and the NSA says they 'kept President Roosevelt informed of every Japanese diplomatic and political policy turn.' To believers, that means he must have known.
'MAGIC didn't tell Roosevelt and other government leaders what the Japanese military was planning,' the NSA's history says.
The NSA's account explains the gap. 'MAGIC didn't tell Roosevelt and other government leaders what the Japanese military was planning,' it says. 'Those ciphers and codes had largely resisted the efforts of American cryptologists to break them.' Any investigation, the NSA adds, 'would be as much a revelation of what we DIDN'T know as of what we DID know.'
There were eight. The Roberts Commission was hostile to the Hawaii commanders, Gen. Walter Short and Adm. Husband Kimmel, and exonerated Washington. The Army Pearl Harbor Board censured Generals Marshall and Gerow. The Naval Court of Inquiry cleared Kimmel and blamed Admiral Stark. The last, a joint congressional investigation that opened on 15 November 1945, saw all relevant classified documents, including the MAGIC translations. Its 1946 findings spread the blame among the Hawaii commanders and the War and Navy Departments. A minority report also censured Roosevelt, but, like the majority, found senior officials in Washington and the Hawaii commanders culpable for the disaster.
In the NSA's words, 'Kimmel and Short would bear the onus for the disaster,' and the arguments continued. As one of Kimmel's lawyers wrote to him in 1953, in words the NSA quotes: 'Pearl Harbor never dies, and no living person has seen the end of it.'
Origins
The NSA's history says that within days of the 7 December 1941 attack there were calls for an investigation, and that the eight inquiries never settled the issue 'for many people.' It says the following fifty years brought a stream of 'revisionist' histories in which conspiracies 'to suppress intelligence by Churchill, Roosevelt, and others would be "exposed."'
The Claims
- Roosevelt had intelligence that Pearl Harbor would be hit and kept it from the commanders in Hawaii.
- U.S. codebreakers had read Japan's attack plans.
- The attack was allowed to happen to overcome American opposition to entering the war.
Key Evidence
- U.S. codebreakers really were reading Japan's top diplomatic traffic. The NSA says that from mid-1940 American cryptologists 'had read the most sensitive Japanese diplomatic messages and had kept President Roosevelt informed of every Japanese diplomatic and political policy turn.' This intelligence was code-named MAGIC.
- Washington officials were blamed. The NSA says the 1944 Army Pearl Harbor Board censured Generals George Marshall and Leonard Gerow, and the 1944 Naval Court of Inquiry blamed Admiral Harold Stark for failing to adequately advise Admiral Kimmel. A 1946 congressional minority report 'also censured Roosevelt.'
The Evidence Against
- The NSA says 'MAGIC didn't tell Roosevelt and other government leaders what the Japanese military was planning,' because Japan's military 'ciphers and codes had largely resisted the efforts of American cryptologists to break them.'
- For the 1945–46 joint congressional investigation, the NSA says the Truman administration 'released all of the relevant classified documents, including the MAGIC translations.' The committee's findings 'apportioned the blame among all the principals: Hawaiian area commanders and the War and Navy Departments.'
- Even the minority report that censured Roosevelt concluded, 'like the majority findings,' that a list of senior officials and the Hawaii commanders were culpable. The NSA's summary describes failures of preparation and warning, not a finding that anyone knowingly let the attack happen.
Documents & Sources
- Gov DocumentOfficial RecordThe Investigations (National Security Agency, Center for Cryptologic History) nsa.gov ↗
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