# Franklin Roosevelt knew Pearl Harbor was coming and let it happen

**No verdict.** The documentary record points overwhelmingly to a genuine intelligence failure (fragmentary warnings buried in noise, not a plot), but a persistent revisionist minority, trained historians among them, keeps the foreknowledge case alive.

Category: Government & Intelligence · Era: World War II · First circulated: 1944 · Believed by: A minority of Americans; strongest among Pearl Harbor revisionist historians
URL: https://theconspiratory.com/theory/pearl-harbor-foreknowledge

## Summary
The most consequential surprise attack in American history, and the one where codebreaking, bureaucratic rivalry and hindsight collide. The mainstream case is intelligence failure, not conspiracy, but the debate has never fully closed.

## The claim
That President Franklin D. Roosevelt and his administration had advance knowledge of Japan's plan to attack Pearl Harbor on 7 December 1941, and deliberately withheld warning from commanders in Hawaii so that the attack would succeed and drag a reluctant United States into World War II.

## Origin and timeline
- Oct 1940: Naval intelligence officer Arthur McCollum writes a memo proposing eight actions to pressure Japan, later cited by revisionists as evidence of a plan to provoke war.
- Sep–Dec 1941: US codebreakers, reading Japan's PURPLE diplomatic cipher, intercept a 'bomb plot' message asking Tokyo's Honolulu consulate to grid-map ship positions in Pearl Harbor.
- 7 Dec 1941: Japan attacks Pearl Harbor without a declaration of war, sinking or damaging 19 ships and killing more than 2,400 Americans.
- 1944–1946: Nine US investigations, including a joint congressional inquiry, examine why the attack was a surprise; none finds that Roosevelt knew the target or time in advance.
- 2000: Journalist Robert Stinnett publishes 'Day of Deceit,' reviving the foreknowledge claim using declassified intercepts; mainstream historians reject its central argument.

## The evidence, claim by claim
- Claim: Washington had broken Japan's codes, so it must have known the attack was coming.
  Evidence: Codebreakers had broken PURPLE, Japan's diplomatic cipher, but not JN-25, its main naval operational code; by December 1941 analysts could read only a small fraction of naval traffic. The diplomatic intercepts showed Japan preparing for war and drifting toward a break in talks, but none disclosed Pearl Harbor as the target, the date, or the method.
- Claim: The McCollum memo proves the administration had a plan to provoke Japan into striking first.
  Evidence: The 1940 memo did propose pressuring Japan and predicted this might lead to war, but it was a mid-level planning paper, not adopted policy, and no evidence shows Roosevelt saw it or acted on it as a blueprint. Its own text reads as aimed at deterrence and containment, not engineering a surprise attack on Hawaii.
- Claim: The 'bomb plot' message shows Washington was tracking a strike on the fleet at Pearl Harbor.
  Evidence: That September 1941 intercept, asking Japan's Honolulu consulate to grid-map ship berths, was real and, in hindsight, was a genuine missed warning. But at the time it was one of many Japanese intelligence-gathering requests about ports across the Pacific, was not flagged as unique, and was not shared with Hawaii's commanders: a failure of prioritization, not proof anyone in Washington knew what it meant.

## Why people believe it
- The scale of the disaster (the deadliest surprise attack in American history up to that point) creates a powerful instinct that failure this total must have been intended by someone.
- The government really did withhold codebreaking intelligence from the Hawaii commanders and later scapegoated them, which lends genuine credibility to the idea that something was being covered up.
- Roosevelt undeniably wanted the United States in the war against Nazi Germany, and it is an easy, if unproven, step from 'wanted war' to 'engineered this particular attack.'

## Open questions
- Why the intelligence Washington already had (above all the September 1941 'bomb plot' message ordering a grid-map of ship berths at Pearl Harbor) never reached Admiral Kimmel or General Short in a form that triggered a full alert is still not fully settled. The Pentagon's own 1995 review, led by Under Secretary of Defense Edwin Dorn, confirmed the intelligence was withheld from Hawaii, but did not establish exactly why: overload, Army-Navy turf-guarding, a judgment that the signal wasn't unique enough to flag, and plain bureaucratic failure have all been proposed. Nine official investigations between 1941 and 1946, and the Dorn review nearly fifty years later, have narrowed the question without fully closing it.
- A genuine historiographical fight continues between revisionists and mainstream historians, not a settled consensus against fringe bloggers. Robert Stinnett's Day of Deceit and John Toland's Infamy both argue for deliberate foreknowledge using declassified documents, but specialists have directly rebutted their central claims: cryptologic historian David Kahn identified basic errors in Stinnett's reading of naval codebreaking records, and Kahn and fellow historian John Zimmerman traced Toland's claim that intelligence had tracked Japanese carriers near Hawaii to a misread abbreviation in a Dutch officer's diary that most likely described ships near the Marshall Islands instead. Gordon Prange's decades of research reached the opposite conclusion entirely. Both camps are working from real archival material rather than invention, which is part of why the fight has never fully resolved.
- Some of the underlying record stayed classified for decades after the war. Stinnett has said his research relied on Freedom of Information Act requests filed over roughly sixteen years, and on more than 200,000 pages of naval records that reached him only through declassification: meaning the documentary picture was still being assembled, and re-argued, more than fifty years after the attack. Whether anything relevant remains unreleased is, by definition, unknown.
- Congress found in 1999 that Kimmel and Short had each performed their duties 'competently and professionally' and that the Pearl Harbor losses were not the result of dereliction of duty by either man, and recommended they be posthumously restored to their wartime ranks; a 2000 defense authorization act repeated the recommendation. No president has ever acted on it. Whether that reflects lingering doubt about the full picture, institutional inertia, or simple political caution has never been officially explained.

## Sources
- Investigation of the Pearl Harbor Attack: Report of the Joint Committee (79th Congress), U.S. Congress, Record Group 128, National Archives (1946): https://archive.org/details/investigationofp0000unit
- Memorandum for the Director: Estimate of the Situation in the Pacific (the McCollum memo), Office of Naval Intelligence, declassified National Archives record (1940): https://en.wikisource.org/wiki/McCollum_memorandum
- Pearl Harbor: Warning and Decision, Roberta Wohlstetter (Stanford University Press) (1962)
- At Dawn We Slept: The Untold Story of Pearl Harbor, Gordon W. Prange (McGraw-Hill) (1981)
- Day of Deceit: The Truth About FDR and Pearl Harbor, Robert B. Stinnett (Free Press) (2000)
- Attack on Pearl Harbor, National Archives (Legislative Archives feature on the investigation record): https://www.archives.gov/legislative/features/pearl-harbor
- Infamy: Pearl Harbor and Its Aftermath, John Toland (Doubleday) (1982)
- Memorandum for the Deputy Secretary of Defense: Advancement of Rear Admiral Kimmel and Major General Short (the Dorn Report), Edwin Dorn, Under Secretary of Defense, U.S. Department of Defense (1995): https://www.ibiblio.org/pha/pha/dorn/dornmemo.html
- Pearl Harbor advance-knowledge conspiracy theory, Wikipedia: https://en.wikipedia.org/wiki/Pearl_Harbor_advance-knowledge_conspiracy_theory

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