For a long time, when I started school, my plan was to get a BA in History, with a Minor in Military studies.
Since then, the plan has changed.
But at the time, I always thought it would be a good basis to try to get a job at a thinktank or war college.
Since then, I have learned that most war colleges reserve teaching posts for actual military personnel, but I am still curious about how one ends up being part of a thinktank.
It seems that were I to do the History with the military focus, that would pretty much be my only chance to actually use this knowledge.
A colleague of mine taught at one of the military staff colleges. She has a PhD from a well-known university, just as you’d expect from most other graduate level instructors or professors.
You may wish to look into getting an internship at a think tank. I suggest you spend some time looking at think tanks and see which ones cover fields you are interested in, then send them a resume and cover letter. But as has been said, getting a job at a think tank really isn’t any different than getting a job in sales or marketing or burger flipping. There are entry level positions in all of those areas, and you just have to start applying in order to find one of those jobs.