I want it to be realistic and historically accurate in as many ways as possible, including the attitudes of the time. And then, be a good film for the other types of film that it is.
I think that characterization can get in the way, especially if the film fails to show how war dehumanizes people, at least, if that’s historically appropriate.
Pacifist though I am, I’m also very interested in military history, and I enjoy war games and violent games and films, for fun as well as for interest. And I tend to think it is often a mistake which backfires when films intentionally try to give an anti-war message. It’s an unwise mistake because it doesn’t need to be done, and adds a layer of fakeness to the pacifist message. War and violence are terrible, horrible things which only need to be presented realistically in order to make a pacifistic impression.
e.g. Midway
BTW, I think the best war film (for my bullet) overall may be The Longest Day, though it may not be the absolute most realistic, nor does it show horror and humanity the best.