A settlement without defenses is unlikely to resist capture. Here we look at the types of fortifications a settlement may need.
While not an actual fortification, a cleared area devoid of trees often surrounds a settlement to prevent opposing forces from approaching unseen. Decide how far out this region extends from the city or whether it’s been done at all. Trees might have been left there as a trap and the locals know better than to set foot inside.
Whether towers for archery or another missile defense, lookout towers provide the opportunity to rain missiles down on approaching forces. They could be located all around the settlement, but we should establish what’s going to attack and from which direction. An army can typically approach from only one side; if they can do so from all sides, then this settlement isn’t in a good location for defense. The direction from which the primary threat comes will have more towers, as will major entrances. A city wall might also provide an inner walkway that means archers can be anywhere and move easily; in this scenario, actual towers might be mostly for lookouts.
In fantasy settings, the castle is a major part of many settlements and the center of life. In addition to a strategic position for firing upon attackers and making itself harder to conquer, castles are used to shelter locals in case of emergency or invasion. In a village or small town, the entire population might fit in the castle. They’ll be overflowing the rooms, sleeping in halls, maybe even in the courtyard, but it’s better than being in the path of an opposing army. However, in larger settlements, not everyone’s going to fit. No matter the size of the community so housed, there must be enough food and water to outlast a siege or surrender is inevitable. In cities, the castle’s fortifications will be augmented by the city wall, which can protect a larger population and the city itself.
Small settlements sometimes have a wall, which controls entrance and exit in addition to providing protection from attack. Some are only waist high and made of stones, which may seem pointless to us for being so easily climbed over, but limited material might be the reason for this. A settlement near mountains is unlikely to have such small walls of stone. Similarly, a low wall of timber when a forest stands near seems less believable.
We should decide what this wall is designed to keep out. Anything with the ability to control fire will burn down wooden walls, though this is a time-consuming way to remove one, but a wooden wall can still slow an attacking force, especially if it’s comprised of less-intelligent creatures, such as animals or monsters.