The roots of warfare are often found in the middle of a story. If you have tons of stuff people want and don't protect it somebody's going to take it. Some societies do it defensively, some native american societies will build these tall sorts of abodes or in rock cliffs where they can pull up ladders if the dangerous raiding people's nearby them show up. Not choosing anything is an option that will get your people wiped out taken into slavery absorbed and eventually have them disappear.