Did FDR know about the Pearl Harbor attack before it happened?

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Did FDR Have Prior Knowledge of Pearl Harbor?

The Japanese attack on the U.S. Naval Base at Pearl Harbor destroyed almost 200 U.S. aircraft, took 2,400 lives, and swayed Americans to support the decision to join World War II.

Within 24 hours, Congress had reversed its position of neutrality in World War II, declaring war on Japan and starting the chain of events that led to the U.S. forces joining the full war.

SEE MORE: Rare new images reveal details of seaplane lost in Pearl Harbor attack

Some claim there is evidence to suggest that President Franklin Roosevelt knew about plans for the attack in advance, and allowed it to happen specifically to justify entering the war.

Journalist John Flynn first emerged with the accusation in 1944.​

See images of the attack on Pearl Harbor:
Attack on Pearl Harbor - Dec. 7, 1941
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Did FDR know about the Pearl Harbor attack before it happened?
** FILE ** In this U.S. Navy file photo, a small boat rescues a USS West Virginia crew member from the water after the Japanese bombing of Pearl Harbor, Hawaii on Dec. 7, 1941 during World War II. Two men can be seen on the superstructure, upper center. The mast of the USS Tennessee is beyond the burning West Virginia. On Dec. 7, 1941, Japanese Imperial Navy navigator Takeshi Maeda guided his Kate bomber to Pearl Harbor and fired a torpedo that helped sink the USS West Virginia. On Sunday Dec. 3, 2006, Maeda and John Rauschkolb a crewman aboard the West Virginia at the time of the attack, met face-to-face for the first time and shook hands. (AP Photo)
The destroyer USS Shaw explodes after being hit by bombs during the Japanese surprise attack on Pearl Harbor, Hawaii, December 7, 1941. (AP Photo)
** FILE ** American ships burn during the Japanese attack on Pearl Harbor, Hawaii, in this Dec. 7, 1941 file photo. (AP Photo, File)
Japanese attack on Pearl Harbour, December 7, 1941, United States, Japan - World War II, Narional archives. Washington. (Photo by: Photo12/UIG via Getty Images)
In this image provided by the U.S. Department of Defense, destroyers in drydock at Pearl Harbor in Hawaii are battered by bombs after Japanese sneak attack on Dec. 7, 1941. Background in dock is battleship Pennsylvania, which suffered only minor damage. Destroyers are Downes, left, and Cassin, right. Machinery and fittings were transferred to new hulls and the destroyers were never stricken from Navy's active list. (AP Photo/U.S. Department of Defense)
The battleship USS West Virginia is seen afire after the Japanese surprise attack on Pearl Harbor, Hawaii, on December 7, 1941. (AP Photo)
FILE - In this Dec. 7, 1941 file photo, smoke rises from the battleship USS Arizona as it sinks during a Japanese surprise attack on Pearl Harbor, Hawaii. Saturday marks the 72nd anniversary of the attack that brought the United States into World War II. (AP File Photo)
US ships 'Virginia' and 'Tennessee' on fire after the Pearl Harbor attack, December 7, 1941, World War II, Washington, National archives, . (Photo by: Photo12/UIG via Getty Images)
Officers' wives, investigating explosion and seeing smoke pall in distance on Dec. 7, 1941, heard neighbor Mary Naiden, then an Army hostess who took this picture, exclaim "There are red circles on those planes overhead. They are Japanese!" Realizing war had come, the two women, stunned, start toward quarters. (AP Photo/Mary Naiden)
This is the front page of the Honolulu Star-Bulletin announcing the Japanese attack on Pearl Harbor, Dec. 7, 1941. (AP Photo)
U.S. soldiers at the Presidio in San Francisco gather around the bed of one of their comrades, Dec. 7, 1941, to read an extra reporting of the bombing of Pearl Harbor, Hawaii, by the Japanese. (AP Photo/John Young)
This picture, taken by a Japanese photographer, shows how American ships are clustered together before the surprise Japanese aerial attack on Pear Harbor, HI., on Sunday morning, Dec. 8, 1941. Minutes later the full impact of the assault was felt and Pearl Harbor became a flaming target. (AP Photo)
An undamaged light cruiser steams out past the burning USS Arizona and takes to sea with the rest of the fleet during the Japanese aerial attack on Pearl Harbor, Hawaii, on Dec. 7, 1941 during World War II. (AP Photo/U.S. Navy)
Torpedoed and bombed by the Japanese, the battleship USS West Virginia begins to sink after suffering heavy damage, center, while the USS Maryland, left, is still afloat in Pearl Harbor, Oahu, Hawaii, Dec. 7, 1941 during World War II. The capsized USS Oklahoma is at right. (AP Photo/U.S. Navy)
FILE-- The infamous attack on Pearl Harbor on December 7, 1941. The USS Arizona is pictured in flames after the Japanese attack. On Sunday, Dec. 7, 1997, the 56th anniversary of the attack that drew the United States into World War II, two Navy men who survived the battle are scheduled to have their ashes scattered on the waters above the battleship. It is an honor extended to those who survived the attack while serving on another ship, or those who served on the Arizona before the attack.(AP Photo/U.S. Navy,File)
In this photo provided by the U.S. Army, a pall of smoke rises from fires started during the Japanese bombing of Hickam Field at Pearl Harbor, Hawaii, Dec. 7, 1941. (AP Photo/U.S. Army)
As the deck of the capsized battleship USS Oklahoma breaks water, damage and corrosion to her superstructure are shown on May 24, 1943 at Pearl Harbor, Hawaii. The Oklahoma capsized after being hit with torpedoes in the Japanese attack on Pearl Harbor on Dec. 7, 1941 during World War II. (AP Photo)
A Japanese dive bomber goes into its last dive as it heads toward the ground in flames after it was hit by Naval anti-aircraft fire during surprise attack on Pearl Harbor, Dec. 7, 1941. (AP Photo)
FILE - In this undated file photo, wreckage identified by the U.S. Navy as a Japanese torpedo plane was salvaged from the bottom of Pearl Harbor following the surprise attack Dec. 7, 1941. An excavation crew recently made a startling discovery at the bottom of Pearl Harbor when it unearthed a skull that archeologists suspect is from a Japanese pilot who died in the historic attack. Archaeologist Jeff Fong of the Naval Facilities Engineering Command Pacific described the discovery to The Associated Press and the efforts under way to identify the skull. He said the early analysis has made him "75 percent sure" that the skull belongs to a Japanese pilot. (AP Photo, file)
A mass of twisted metal wreckage lay along a Honolulu street after the city had been attacked by Japanese planes Dec. 7, 1941. (AP Photo)
U.S. Navy seamen examine the wreckage of a Japanese torpedo plane shot down at Pearl harbor during the Japanese raid on Pearl Harbor, Dec. 7, 1941. (AP Photo)
The wing of a Japanese bomber shot down on the grounds of the Naval Hospital at Honolulu, Hawaii, Dec. 7, 1941. (AP Photo)
Japanese attack on Pearl Harbor, December 7, 1941, World War II, Washington, National archives, . (Photo by: Photo12/UIG via Getty Images)
Firemen and civilians rush to the scene with fire hoses to save homes and stores in the Japanese and Chinese sections of Honolulu, Hawaii, on Dec. 7, 1941. As Japanese aviators rained bombs on Pearl Harbor, starting war in the Pacific, offshore properties are also wrecked and burned. (AP Photo)
Selling papers on Dec. 7, 1941 at Times Square in New York City, announcing that Japan has attacked U.S. bases in the Pacific. (AP Photo/Robert Kradin)

Decades later in 1999, former sailor Robert Stinnett came forward with claims he'd uncovered evidence that the FDR administration deliberately provoked and allowed the Japanese to attack specifically to bring the U.S. into the war.

According to Stinnett the U.S. had cracked Japanese encryption codes years before the attack, therefore FDR knew about it. Those claims have been debunked by historians, who insist those codes were not yet deciphered.

Stinnett also claimed U.S. intelligence would have been able to intercept radio signals from the Japanese planes crossing the Pacific, but former Japanese pilots have since testified that their planes were stripped of all equipment that would have been traceable, making them "radio silent."

There is some proof that Roosevelt had information suggesting there was a possibility of such an attack.

A memo released to the public in 2011, sent to Roosevelt three days before the 1941 attack, included warnings from naval intelligence that Tokyo was focused on Hawaii.

The declassified file included warnings from the Office of Naval Intelligence sent on December 4 that read in part, "In anticipation of open conflict with this country, Japan is vigorously utilizing every available agency to secure military, naval and commercial information, paying particular attention to the West Coast, the Panama Canal and the Territory of Hawaii."

SEE MORE: Survivor of USS Arizona from Pearl Harbor attack dies at 100

Additionally, diary entries by then-Secretary of War Henry Stimson reveal that he had a meeting with Roosevelt just ten days before the attack in which FDR pondered how to maneuver the Japanese into firing the first shot. Years later, Stimson revealed that the commanders at Pearl Harbor had been warned of the possibility of attack, and that he was surprised at how unprepared they were.

Ultimately, the majority of mainstream historians reject the idea that Roosevelt knew of the exact details of the Pearl Harbor attack, but also agree that the administration underestimated the threat coming from the Japanese empire.

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