Capturing bases
Defeat a base's defenders, then march infantry in to take it.
A base is defended by its defences and by the troops standing near it. Once they are gone, its buildings stand idle: the base is neutralised.
To take it, you need infantry standing at the base, out of their transport. Tanks, aircraft, ships and missiles can beat the defenders, but only Assault and Missile Squads can capture.
When you capture a base, its standing buildings become yours. If every building was destroyed, you choose whether to keep the empty base or tear it down.