I have been defending this manga in the comments, but this is starting to get to me. For one, bronze makes for some pretty crappy farming tools. Even during the Bronze Age farming equipment was often made of iron. Iron at that tech level might have not been good for weapons--being heavy, hard, and brittle--but the comparative softness and much greater expense of bronze makes it even worse for farming. Also, the whole point of a standing army is to have people dedicated to fighting, and not farming. If you make them have to focus on growing their own food you're better off just conscripting or getting volunteers as needed for a war.