As I was watching "What You Leave Behind" the other night, I was struck by something: Odo ends the war by being the most Starfleet-esque person in the show! He reaches out and shows compassion for an enemy, conquering the enemy by making her a friend.
If only Starfleet had remembered their principles much earlier, the war might have ended sooner!
I don't mean to be a Dominion apologist, but it takes two to war. Starfleet was always meant to be a force for good (much like America's modern navy, if the ads are to be believed), and the moment they stopped acting like that, they damned themselves to an interminable war.