With an exception of Airfield, that has the role of servicing Planes, all other Military buildings have one and one task only: production of military force.
Airfield building is designated to station jet fighters and tactical bombers. It provides slots for 4 planes in any combination of numbers. It requires Headquarters LVL 3.
Building Airforce is the main and only task of Aviafactory. It requires Headquarters LVL 2.
Assault Vehicle Factory is a production building with the goal of creating Assault Vehicles. It requires Headquarters and Barracks LVL 1.
Barracks are production building in charge of training infantry units. It requires Headquarters LVL 1.
Shipyard is Naval production building. It requires the surface of the water to build and Headquarters LVL 2.
Space System is Military secret weapon/building, capable of breaking entranched enemies.
Special Vehicle Factory, as the name says, is creating the class of Special Vehicles. It requires Headquarters LVL 2.