You might also want to cross-promote your sub in some of the many other history-related subreddits. There are already dozens of them.

For what it's worth, /r/history occupies a similar niche, though it's got mostly links, which seems to not be the point of your subreddit.

/r/AskHistory isn't loose enough for you?

Out of curiosity, how strict will be the rules for what is said and such? Do you have a rough outline of what you'll be enforcing in respect to rules and argument? Maybe a Godwin's Law decree to keep it within logical constraints and such?

Here is the link for the lazy /r/historydiscussions