… before we get into the design of point defenses, we should talk about what these are for. Generally, fixed point defenses of this sort in the pre-modern world are meant to control the countryside around them (which is where most of the production is). This is typically done through two mechanisms (and most of point defenses will perform both): first by housing the administrative center which organizes production in the surrounding agricultural hinterland (and thus can extract revenue from it) and second by creating a base for a raiding force which can at least effectively prohibit anyone else from efficiently extracting revenue or supplies from the countryside. Consequently if we imagine the extractive apparatus of power as a sort of canvas stretched over the countryside, these fortified administrative centers are the nails that hold that canvas in place; to take and hold the land, you must take and hold the forts.
In the former case, the fortified center contains three interlinked things: the local market (where the sale of agricultural goods and the purchase by farmers of non-agricultural goods can be taxed and controlled), a seat of government that wields some customary power to tax the countryside through either political or religious authority and finally the residences of the large landholders who own that land and thus collect rents on it (and all of these things might also come with significant amounts of moveable wealth and an interest in protecting that too). For a raiding force, the concentration of moveable property (money, valuables, stored agricultural goods) this creates a tempting target, while for a power attempting to conquer the region the settlement conveniently already contains all of the administrative apparatus they need to extract revenue out of the area; if they destroyed such a center, they’d end up having to recreate it just to administer the place effectively.
In the latter case, the presence of a fortified center with even a modest military force makes effective exploitation of the countryside for supplies or revenue by an opposing force almost impossible; it can thus deny the territory to an enemy since pre-industrial agrarian armies have to gather their food locally. We have actually already discussed this function of point defenses before: the presence of a potent raiding force (typically cavalry) within allows the defender to strike at either enemy supply lines (should the fortress be bypassed) or foraging operations (should the army stay in the area without laying siege) functionally forcing the attacker to lay siege and take the fortress in order to exploit the area or move past it.
In both cases, the great advantage of the point defense is that while it can, through its administration and raiding threat, “command” the surrounding hinterland, the defender only needs to defend the core settlement to do that. Of course an attacker unable or unwilling to besiege the core settlement could content themselves with raiding the villages and farms outside of the walls, but such actions don’t accomplish the normal goal of offensive warfare (gaining control of and extracting revenue from the countryside) and peasants are, as we’ve noted, often canny survivors; brief raids tend to have ephemeral effects such that actually achieving lasting damage often requires sustained and substantial effort.
All of which is to say that even from abstract strategic reasoning, focusing considerable resources on such fortifications is a wise response to the threat of raids or invasion, even before we consider the interests of the people actually living in the fortified point (or close enough to flee to it) who might well place a higher premium on their own safety (and their own stuff!) than an abstract strategic planner would. The only real exception to this were situations when a polity was so powerful that it could be confident in its ability to nearly always win pitched battles and so prohibit any potential enemy from getting to the point of laying siege in the first place. Such periods of dominance are themselves remarkably rare. The Romans might be said to have maintained that level of dominance for a while, but as we’ve seen they didn’t abandon fortifications either.
Bret Devereaux, “Collections: Fortification, Part III: Castling”, A Collection of Unmitigated Pedantry, 2021-12-10.
March 19, 2025
QotD: The purpose of fortification
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