A piece of trivia:
"Wardrobe standards were so strict that soldiers during the Virginia filming were not allowed to wear their own civilian Underarmor (tm) or GoreTex (tm) warmth clothing under their uniforms - as real National Guardsmen so often do during maneuvers. This was despite filming on what turned into the coldest days of 2004 - and wearing light-weather BDUs (BattleDress Uniforms)."
Why would Steven Spielberg not allow the soldiers to wear under clothing meant to keep them from freezing? I mean, what the HECK!
Kay: Senators and presidents don't have men killed.
Michael: Oh, who's being naive, Kay?