With the number of Cold Resistance Level soldiers in the Nine Towns, let alone a thousand-man army, each town could easily muster at least four to five troops. However, it's impossible for all towns to rally all of their Cold Resistance Level soldiers for military service.
Town operations must continue, and normal hunting and gathering activities must not stop. Each town's various agencies and all jurisdictions within the territory need people to govern. All these tasks rely on Cold Resistance Level soldiers to be done.
Joining the army is different from other things; once you become a soldier and join as a member of the army, you can't leave the camp casually.
Moreover, maintaining an army involves not-low daily consumption of war armor, weapons, healing pills, cultivation materials, and so on…
Considering all these factors, throughout the Nine Towns of Moao Mountain, only the most powerful Northern Three Towns can form an army using Cold Resistance Level soldiers.
