Which would itself create a paradox, because a person with an in depth, detailed knowledge of history would distinguish himself as a great seer or prophet of the, 'future'. i.e. imagine showing up at the US War Department on Friday, December 5, 1941. People might not take you seriously that day, but would probably want to talk with you at length the following Monday.
Here's how a defender of the Principle would answer that:
You would not be able to show up at the War department on December 5th, or at any time before the actual attack. Nature would prohibit it, just as nature prohibits a person from jumping 50 feet into the air.
Perhaps your car would brake down on the way. Or perhaps you would fall into a coma on December 4th, and not wake up until December 8th.
I'm not saying I agree with any of this. But that's what a defender of the Principle would say.
In the TV movie Time Element, a man goes to sleep in New York in 1958 and wakes up in a Honolulu hotel room in early December, 1941. At the hotel bar, he meets a sailor from the USS Arizona and tries to convince him not to return to his ship later that night. Of course everyone in the bar thinks he's crazy, and he's soon taken in to custody to be given a psychological examination.
When asked by his examiners who the president is, he at first answers, Eisenhower, then remembering it's 1941, corrects himself, saying Roosevelt. But when asked who the vice president is, he answers incorrectly Harry Truman, bringing stares of wonderment from the interrogators. He tells them that FDR will die and Truman will succeed him, then turns around and asks them if they know the meaning of terms such as rock and roll and Sputnik. He manages to escape immediately afterwards. Most of the interrogators conclude that he's a nut, but one of them is convinced that he is not crazy.