There has long been a strain of conspiracy theory, which had significant evidence in its favor nonetheless, that Roosevelt knew that the Japanese were going to attack Pearl Harbor and allowed the attack to go ahead anyway.
This has long been a favorite of rightwingers then and now. Conservatives at the time thought Roosevelt was a traitor who had deliberately filled his Cabinet with many Soviet spies to whom he gave much classified information.
This is the Commie spy network that Joe McCarthy, etc. set about going after in the 1950’s during the Red Scare. There doesn’t seem to be good evidence for this.
To this day, standard anti-Semitism is almost always rightwing or far rightwing and is heavily tied in with anti-Communism among other things such as anti-modernism and anti-liberalism, two movements that the Jews were seen leading.
Anyway, there were many hard conservatives in the Pentagon around the time of World War 2, and quite a few of them were starting to imbibe the “Jewish Communist threat” line.
Winston Churchill himself was one of the originators of the Jewish Bolshevik hysteria when he made some paranoid and agitated statements along the lines that the Bolshevik revolution was a Jewish one soon after the October Revolution was through.
It was these nutty reactionary anti-Communist anti-Semites in the Pentagon who were responsible for the “Roosevelt knew” line.
Revilo Oliver had worked in intelligence at the Pentagon during the war and later said that Roosevelt had allowed the Pear Harbor attack. Two very conservative admirals stated after the war that Roosevelt should be tried for treason for allowing the attack. These two admirals did not have good evidence for their charges.
Oliver is apparently lying. He was an extreme anti-Communist, a White nationalist racist, a Nazi sympathizer, and a hardcore anti-Semite who later became very active in the early days of the National Review, to show you how tainted the early days of Buckley’s journal were.
Oliver is of course also a Holocaust denier who railed about the bombing of Dresden (which he exaggerated as such types are wont to do) and the Nuremberg trials, which he regarded as an outrageous orgy of murder. Which in some ways it was, unfortunately.
It doesn’t take long to deeply review the case of the Pearl Harbor advance knowledge theory to show that it is nonsense. We never cracked the main code that the Japanese used in the weeks before the attack. The Japanese fleet turned off their radios as they sailed to the attack, a brilliant move.
Radar was in its infancy and worked poorly. Nevertheless a radar operator noticed large blobs on the screen and notified his superiors, who laughed and told him they were clouds. Early radar has a hard time distinguishing between ships and clouds. His observation made it up to a general nevertheless, but the general laughed the blobs off as clouds too.
It is certainly true that Roosevelt was trying to push the Japanese into a corner and many thought he was trying to bait them into a war. I believe that’s pretty uncontroversial. In fact, the US was alarmed at how upset the Japanese were at the US’ moves such as the embargo on oil sales to them.
In fact in the months leading up to the attack, the US increasingly felt that the Japanese were getting ready to attack the US. They weren’t sure it was going to happen, but they thought it likely. What they didn’t know was where and when it would take place, and Pearl Harbor was not considered to be a likely a target. The large US garrison the Philippines was considered a more likely target.
Roosevelt definitely wanted war with the Japanese. He had made statements along the lines that no way was he going to allow the Japanese to run amok all over the Pacific, conquering lands and slaughtering the natives while brutally colonizing them.
There was a telegram sent to the Japanese ambassador in Washington the night before the attack telling him that the Japanese government was going to break off relations with the US. It was in an earlier code that had already been broken.
The Pentagon felt that that meant that a Japanese attack may be imminent. However, a warning to that effect sent out to US forces in the Pacific got lost in the shuffle and was only read too late by most of its recipients.
There were 10 full investigations of the Pearl Harbor attack. No foreknowledge of the attack by Roosevelt or anyone else in the administration was ever demonstrated.
Although there is some interesting evidence in favor of this conspiracy theory, at the end of the day it doesn’t seem to hold water and simply seems to be one more club that the Right uses to bash Democrats along with one of the Right’s most hated Democrats of all, Roosevelt.
Furthermore the people who traffic in this theory are pretty unsavory. It is a favorite of a variety of conspiratorial rightwing types, including fanatical anti-Communists, hardcore anti-Semites, neo-Nazis/Nazi sympathizers, Holocaust deniers, White nationalists and other charming folks.