Depends on how it starts, I suppose. Either you're attacking someone else, thus a build-up before deployment would probably fit better. Give time to show the blood, sweat, and tears shed to finally be prepared for battle, then how quickly it can be all stripped from you when you're on the battlefield.
However, if you're BEING attacked, quick and aggressive is usually a better tactic. When war strikes, most people are caught trying to process the situation rather than immediately taking action. It could be much more dramatic that way.
