[Sonic Youth 37]

Check your world map to see who your enemies are and if they're currently hostile or not, that should give you an idea about armies. If you're thinking about raising one, you'll need to make sure you can produce or import enough food, olive oil, fleece, wine, armor (and horses, if you want cavalry) to support your army. To raise an army, you have to build elite houses. To build an elite house, you need spare food, oil, and fleece (not sure about food, but you'll need at least 1 spare oil and fleece) AND to build the home in a high appeal area. Elite citizens don't count in the work force, so they won't deplete your labor. The only thing that is basically a labor drain is the trireme wharf. A fully battle ready wharf takes 100 people, but directing them to stand down allows those 100 to find other jobs.

Also, by default, when you build a palace, you'll start getting Rabble armies (denoted by a hand with a stone flag in the courtyard). These are made of normal citizens and are best used a auxiliary troops in support of hoplites/cavalry. They are effectively useless against foreign invaders.

ALSO! (sorry), the temples of Ares and Artemis will give you 2 companies of super soldiers (Spartans or Amazons, respectively) and the temple of Hephaestus will give you the ability to summon Talos to defend the city. Divine creatures (Talos, Cerberus, Ares' dragon, etc) are good for taking on invading armies, but are poor at battling invading monsters/gods/heroes.