Military buildings
Where troops are trained, and where their gear and supplies come from.
Forge Makes the basic kit troops train and fight with: swords, spears, bows, slings and shields. 
Armory Makes battle axes for berserkers. 
Gunsmith Makes arquebuses and blasting charges. 
Barracks Trains its workers as troops: warriors, spearmen, or the faction's own kind. 
Archery Range Trains its workers to shoot from a distance: archers, or the faction's own kind. 
Monastery Trains monks. Instead of fighting, they convert enemy troops and siege machines to your side, then wait for their faith to return. 
Wagon Yard Sends supply carts to the front so warriors can eat, drink and build siege engines off the roads. 
Stone Press Presses scrap metal and logs into siege stones for catapults and trebuchets.