I'm not sure exactly at what level this film is supposed to be pitched. I think it's going for seriously ridiculous. As such, I think Pitt's purposely aiming to portray a ludicrous, image-obsessed, action-talking, hard-ass, macho military officer. The sort, who in reality, is mostly all shadow no substance i.e. the stereotypical american solider view that the rest of the world has. If Pitt wears sunglasses at any one point and chews gum, the stereotype is complete.

If this is what they are aiming for, then I hope it works. Otherwise...
