Garrisons are groups of men who are stationed in provinces to protect
them, and collect taxes in the name of a castle. Garrisons must be
created with the
garrison order, and must be bound to a castle
located in the same region.
For example, suppose that the region Lesser Atnos had 20 provinces. One of these provinces contains Amber Keep [cy09]. A garrison bound to Amber Keep could be stationed in each of the 20 provinces (including the province containing the castle itself).
Continuing the example, garrison units not in the Lesser Atnos region could not be bound to Amber Keep. The castle a garrison is bound to must be in the same region.
Garrisons can be bound to any castle in the region. If Lesser Atnos had two castles, some of the garrisons could be bound to one, and the rest to the second castle.