Your automatically spawning army is the backbone of your attack and defense. Everyone in the game starts with footmen, but it's in your best interests to upgrade your barracks as soon as possible. Each upgraded barracks improves your base defense and spawns different units, like dryads, skeleton mages, and raiders. People often forget that higher tiers also gets you more hit points on your base. It's fairly easy for an opponent to destroy your Tier One base late in the game.