The objective of first phase of the war was to dislodge the Taliban and Al Qaeda from their strongholds and to gain ground.
The current phase of the war is to surround the remaining Taliban and Al Qaeda and to annihilate them. (This phase is the phase that Colin Powell unfortunately talked Bush Senior into skipping during the Gulf War.)
Battles of annihilation will always be much nastier affairs than battles fought to drive an enemy from the field. Our Afghan allies had great enthusiasm for the latter but, once they controlled the cities, have no motivation or stomach for the former. Tora Bora showed that our Afghan allies are perfectly content to let the enemy slink away in order to avoid a battle of annihilation.
Unfortunately, the dirty business of this battle of annihilation will be one that U.S. infantry will have to shoulder itself.
If I were the commander, my strategy would be to use airpower guided by SF and Predator spotters against the center of the enemy concentration and to deploy well entrenched U.S. infantry along every possible escape route to kill any who try to escape. I would be patient and would not push infantry assaults into the enemy center. Once we have the enemy surrounded, time is on our side and our infantry should fight on ground and positions of our own choosing.
Sounds like that is what's about to happen. Big Red is going in. Expect casualties on both sides to go up sharply.
My concern is that I don't think we can trust our allies. If we really get serious, I think our guys will have to worry just as much about the "allies" at their sides and backs. I wouldn't trust any of the locals.