Ive seen those with Masters teach a class or two for an extra 20 grand a year.
Your friends are lying to you....Try 50 grand for a full time professor and graduate students teaching for tuition reimbursement and stipends.
Go to Barnes and Noble...buy every Military History book they have. Save Your Money...
Which period of history are you interested in? I could see a Masters in Classical History with a specialization in Roman Empire?
European History with a specialization or focus on Napoleonic wars...and Colonization.
I think your focus is too broad...