Castles are a stereotypical feature of the fantasy genre, but for good reason: they're a ubiquitous feature of nearly every non-nomadic society well into the gunpowder era, until artillery finally got powerful enough that "build a better wall" stopped being a useful method of defense.

But castles, like walls, sometimes get simplified and misunderstood. So let's take a look at the many purposes they once served.

(Before we do, though, a note on terminology: strictly speaking, "castle" refers only a category of European fortified residence between the 9th and 16th centuries or thereabouts. I'm using the term far more generically, in a way that would probably make a military historian's teeth hurt. There's a whole spectrum of fortification, from single small buildings to entire cities, whose elements also vary according to time and place and purpose, and probably "fortress" would be a better blanket term for me to use here. But because "castle" is the common word in the genre, I'm going to continue referring to my topic that way. You can assume I mean a fortified building or complex thereof, but not an entire settlement -- though some of my points will apply to the latter, too.)

Most obviously, castles are defensive fortifications. What a wall does for the territory behind it, a castle does for everything within its bounds -- extending, in the more complex examples, to multiple layers of walls and gates that can provide fallback positions as necessary. This means that often (though not always; see below) the land outside is cleared, access is restricted, regular patrols go out if danger is anticipated, and so forth.

This defensive function is more concentrated, though, because a castle is frequently also a depot. If you're going to store anything valuable, you want it behind strong walls, whether that's food stores, military equipment, or money. Or, for that matter, people! Prisoners will have to stay put; nobles or other figures of importance are free to wander, but when trouble threatens, they have somewhere (relatively) safe to retreat. This can become a trap if the enemy lays siege to the place, but when you can't flee, holing up is the next best choice.

That category of valuables also includes records. Fortified sites are built not just for war, but for administration; given how much "government" has historically amounted to "the forcible extraction of resources by an elite minority," it's not surprising that defensive locations have often doubled as the places from which the business of government was carried out. Deeds of property, taxation accounts, military plans, historical annals, maps -- those latter are incredibly valuable resources for anybody wanting to move through or control the area. Someone who knows their castle is about to fall might well try to screw over the victor by burning records, along with any remaining food stores.

It's not all about hiding behind walls, though. As with a border fortification, a castle serves as a point from which military force can sally out. Even though these sites occupy very small footprints, they matter in warfare because if you don't capture them -- or at least box them in with a besieging detachment -- before moving on, they'll be free to attack you from behind, raid your supply train, and otherwise cause you problems. Sometimes that's a risk worth taking! In particular, if you can move fast enough and hit hard enough, you might pass a minor castle to focus your attention on a more significant one, leaving the little places for mopping up later. (Or you won't have to mop up, because the fall of a key site makes everybody else capitulate.)

Castles are also economic centers. Not only do they organize the production and resource extraction of the surrounding area, but the people there generally have more money to spend, and their presence entails a demand for a lot of resources and some specialized services. As a consequence, a kind of financial gravity will draw business and trade toward them. Even when the key resources are somewhere other than the castle itself -- like a water-powered mill along a nearby stream -- they're very likely owned by the guy in the castle, making this still the regional locus for economic activity. If there's a local fair, be it weekly, monthly, or yearly, it may very well be held at the castle or nearby; regardless of location, the castle is likely to authorize and oversee it.

This economic aspect may lead to the creation of a castle town: a settlement (itself possibly walled) outside the walls, close enough for the inhabitants to easily reach the castle. In Japan, the proliferation of castle towns during the Sengoku period was a major driver in the early modern urbanization of the country, and I suspect the same was true in a number of European locales. Eventually you may wind up with that thing I said I wasn't discussing in this essay: an entire fortified settlement, with a castle attached on one side or plonked somewhere in the middle. It's not a good idea to let the buildings get too close to the walls -- remember that you want a clear field in which to see and assault attackers, and you don't want them setting fire to things right by your fortifications -- but the town can contribute to the idea of "defense in depth," where its wall adds another barrier between the enemy and the castle that is heart of their goal.

You'll note that I've said very little about the specific design of these places. That's because there is an ocean of specialized terminology here, and which words you need are going to depend heavily on the specifics of context. How castles get built depends on everything from the money available, to the size and organization of the force expected to attack it, to the weapons being used: nobody is going to build a star fort to defend against guys with bows and arrows, because you'd be expending massive amounts of resources and effort that only become necessary once cannons enter the field. Moats (wet or dry), Gallic walls, hoardings, crenelations, machiolations, arrowslits, cheveaux de frise . . . those are all things to look into once you know more about the general environment of your fictional war.

But back to the castles as a whole. Most of the time, they "fall" only in the sense that they fall into the hands of the attacker. A section of the wall may collapse due to being sapped from below and pounded above, but it's rare for the place to be entirely destroyed . . . in part because that's a lot of work, and in part because of all the uses listed above. Why get rid of an extremely expensive infrastructure investment, when you could take advantage of it instead? Wholesale destruction is most likely to happen when someone has achieved full enough control of the countryside that he's ready to start kneecapping the ability of his underlings to resist that control.

Or, alternatively, when somebody shows up with cannon and pounds the place into rubble. Functional castles in even the broadest sense of the word finally died out in the twentieth century, when no wall could really withstand artillery and pretty soon we had airplanes to fly over them anyway. But at any technological point prior to that -- and in the absence of magic both capable of circumventing fortifications, and widespread enough for that to be a problem defenders have to worry about -- you're likely to see these kinds of defensive structures, in one form or another.



(originally posted at Swan Tower: https://is.gd/NzFCtO)