These bases define the win conditions of the Strongholds mode. Each Stronghold has infantry, air, and vehicle support structures already attached. Capturing Strongholds increases population capacity.
Atriox sees little value in simulation training, preferring to blood his warriors in actual combat. Pain and fear are the best teachers, for what price is there to failure in the sterile realm of simulations and shadow-enemies? However, there are occasions when monitoring and screening are useful in identifying recruits that have the talent needed to lead Banished forces, and what better test for a new Banished lieutenant than a Stronghold on a chaotic front line?