How do I check difficulty level?

Bluemilk92

I want to continue and old, old, old campaign I had going and I'm having trouble. I want to check which difficulty I set it at as I remember at one point telling myself I could beat Captain. If it's just Sergeant then I'll just continue grinding the mission I'm stuck on but if not I may just start a new campaign seeing as changing difficulty is impossible. I would really appreciate any help! I don't mind opening the save file to look for some sort of tag. Remember, all I'm asking is how to identify which difficulty level a current campaign is set at?