Long before the rise of Valyria, Westeros was divided into countless Petty Kingdoms. In the south, the Reach is consumed by fire as weak kings are set upon from all sides, and strong ones vie for their remains. In Dorne, the deserts run red with blood and in the north four kingdoms struggle for supremacy, even as they face invaders from all sides. As chaos descends upon the lands of Westeros it remains to be seen which Kingdoms shall forge dynasties to last a thousand years, and which will fade into history.
The Night's Watch will be divided into Recruits (light infantry), Stewards (archers), Builders (infantry), and Rangers (elite archer/lancer hybrid cavalry). This means a pretty limited roster, but that's mostly in keeping with the books. The trick for the Watch will be to not fight the Wildlings on their own terms, instead relying on discipline and hit-and-run tactics to hold back the Wildling hordes.
Sounds really nice :)
Why would Stewards and Builders be in combat?
All the men of the Night's Watch are essentially fighters. The best ones become rangers, as they will usually be the only ones who venture beyond the wall, but all of them train to fight.