Well, it depends on how you look at it. Real history, you know dates, facts, and you can research everything. If you're doing a fantasy story with some historical facts then you will have to fill in the blanks - weapons, clothing, culture, events, and so on. Maybe that's what he was trying to say?
real history is better than pretty much anything u could make up
I would advice you, real story. but you need to make sure that behind the story there is a message given to the readers. usually when there is a message behind the story, the reader get attract by the story. during your manga it would be best to follow the journey of one soldier during the war.
Hey, that's exactly what I want to convey to the readers ^_^ Like our independence is all because these all nameless heroes. Though there are two protagonist (the usual, male and female). So the story follows the "journal" of these two soldiers (one officer and one sniper)