Honestly, I could almost make a case for a moderator not needing any knowledge of history, because the stuff we have to deal with typically has very little to do with that.
Most important I'd say is being good with people, and being able to express yourself well.
However, it is quite helpful to be knowledgeable enough about the subjects being discussed to spot a crank, or at least to know how to check into the matter.
For instance, I think of the mods we've had that I'm aware of, the closest we've had to a professional was probably sempaiscuba.
However, the killer skills sempai had that made their moderation the most badass IMHO was not historical knowledge, but rather a background in cyber-defense.
We have a regular Nazi troll, and Sempai has kept them (tempted to use "it" for Nazis) almost completely stymied for the last year.
That being said, @semapiscuba's extensive knowledge in certain areas particularly around archeology has made them an invaluable user, and I dearly hope that continues in the future.
3