This new Movieline article tries to make that determination. Below is a little tease of the full article.
But Gyllenhaal isn’t wrong. Brothers focuses more on the psychological journey of an individual soldier than the structure of military conflict. You could say Brothers reverses the standard war movie formula by featuring the war in the soldier rather than the soldier in the war, and for that reason alone it does deserve some degree of differentiation. But it also begs the larger question: Has the term “war movie” become a bad word?
I think there’s probably some truth in both ideas. It seems more about the after effects of war rather than war itself, but the marketing people would be fools to not try and sell it differently.