[Lurking Libertarian]

There is a short story about that I read once. A man (somehow) was transported to 10’th century Iceland. He thought he would be king. But he was frustrated because he didn’t have access to the tools to make the tools he needed to make the stuff he knew how to make.

"The Man Who Came Early," by Poul Anderson (1956). He knows, for example, that gunpowder is made of sulfur, saltpeter and charcoal, but can't find any saltpeter in medieval Iceland.

The other view-- that a modern man sent into the past could rule the world with his knowledge-- probably originated in Murray Leinster's "Sidewise in Time" (1934).

Probably both versions are correct-- in Anderson's story, the hero is thrown back in time with no warning, but Leinster has his professor pack the books and tools he will need to rule the ancient world.

[null and void]

Lest Darkness Fall by L. Sprague de Camp is a pretty good read too.