On 7 December 1941, Japan attacked the US naval base at Pearl Harbor. It's one of the most notorious surprise attacks in history, but how much of a surprise was it? Did US President Franklin Roosevelt in fact know that the attack was coming and even encourage it as a means of propelling the US into World War Two? In this new episode of Conspiracy, the Pulitzer Prize-winning journalist Steve Twomey joins Rob Attar to tackle the "back door to war" conspiracy theory, explaining why many Americans have been willing to believe in a president's treachery.

The HistoryExtra podcast is produced by the team behind BBC History Magazine.
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