Food

Food is your main currency in the game, everything is bought and sold for food. If you can't make food, your army "starves" and you need to make another farm quickly before you starve to death and lose. Careful though, each farm can only produce a certain amount of food. After that it becomes barren and you can't build another farm on it. There is no way to refresh the farms either, they stay completely barren, even if it switches hands.