In my world a lot of people can fly. It isn't everyone and it isn't all to the same skill level. Some people can only float around a bit, while a master can break the sound barrier. There are enough people like this to form all-flying squads in an army.

Castles in real life are very open to the sky, and while crossbows and other ranged weapons would still exist, I would question their effectiveness against a troop of flying people with more movement options than a walking solider.

How could a castle built for defense be made accounting for assaults from the sky?

EDIT: Mechanics of flight: It is performed 'superman' style, where you can float stationary and move around as if in water. No arm flapping is needed and no 'exhaust' wind shoots out from your body. Flight can really be in any direction but headfirst is generally the best for looking and aerodynamics.

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    $\begingroup$ In our world all people can fly (and, moreover, indirect artillery fire has been a fact of life for more than 150 years), so we make our fortifications underground; for historical examples see the fortifications of Liège or the Cheyenne Mountain Complex. It's strange to see a question asking about the effects of a commonplace and well-known aspect of the present world. $\endgroup$
    – AlexP
    Aug 19, 2017 at 19:13
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    $\begingroup$ @AlexP, the OP's question is not asking about the "effects of a commonplace and well-known aspect of the present world." Please note the medieval-europe tag, during which time nobody could fly. $\endgroup$
    – JBH
    Aug 19, 2017 at 19:16
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    $\begingroup$ @JBH: The question explicitly says that some people can fly; therefore, it is a fake-medieval world where they have (magic-powered) aviation, so in this aspect it's like the present world. Note that having aviation will change the society so much as to erase any resemblance to the real middle ages; for example, there will be nothing like the real-medieval isolation of the many little political structures and there will be nothing like the real-medieval lack of accurate maps. $\endgroup$
    – AlexP
    Aug 19, 2017 at 19:19
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    $\begingroup$ @JBH: How don't they have aviation? In real-medieval Europe they had, you know, bombs and incendiary projectiles. Now they have bombers. And by the very possibility of flight they have airborne troops. And aerial observation. And airborne couriers. This is not medieval Europe. $\endgroup$
    – AlexP
    Aug 19, 2017 at 19:47
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    $\begingroup$ @AlexP This is WB:SE, isn't it? The OP prefaced the question with, "In my world...", right? The OP set rules for his world and for some reason you think the rules aren't acceptable. Please post your objections as an answer or, if you prefer, we can take this into chat because for some reason you're not catching on to the fact that the genetic and/or magical ability to fly does not confer technological advancement. Will it change society? Sure! That's not what the OP's asking about. Will it bring the Industrial Revolution hundreds of years early? No. It might even delay it. $\endgroup$
    – JBH
    Aug 19, 2017 at 20:03

5 Answers 5


Assuming a Middle Ages technological level (you may want to specify) I would assume high towers connected with a web of nets to impair flying attack while providing good visual reckoning.

Battlements would have some coverage to protect from air, even if I presume airborne archers would be much less precise than the ones with their feet firmly on the ground.

I would also suggest a copious array of trained falcons and owls to help in the fight.

Other characteristics would depend heavily on details of these "flying abilities", in particular:

  • would people be able to remain static in a position?
  • how much effort will it take to fly?
  • can they fight effectively while flying?
  • how long can they hover?
  • do they have to flap their arms (impairing aiming capabilities)?


If flight is so common and stead and effortless then it may be better to use bunkers instead of castles.

I strongly suggest to give some limitation to flight, something along the lines:

  • You can fly fast and steady, but it requires concentration, so using another device that requires concentration (e.g.: bow or crossbow) is difficult or impossible; flying attack is limited to a lance kept on rest (tournament style) or sword (scythe style).
  • You can only move from point A to point B, in straight line at chosen speed and attitude.
  • You can not stop; you need to keep a minimum speed to fly smoothly, otherwise you start to wobble (like a real plane).
  • Flight is hard, maneuvering laborious and hovering strenuous.
  • Any combination of the above.

Otherwise it would give too much of an advantage and underground bunkers may be necessary.

Underground bunkers, however, would be more vulnerable to ground attacks, given a medieval setting, as it is difficult to fight back. You can only delay enemy advance to be able to escape via some other route (see the Rolling Stone Doors of Derinkuyu and their usage).

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    $\begingroup$ The webs are great. The falcons and owls are fantastic. $\endgroup$
    – JBH
    Aug 19, 2017 at 18:00
  • $\begingroup$ I will elaborate on the mechanics of flight in my main question, thanks. $\endgroup$ Aug 19, 2017 at 20:09
  • $\begingroup$ Lances would not work by the way as you they are on the ground and you are flying, meaning they have something to brace against and you don't. Shadiversity addresses this problem with centaurs. You would not have a delayed reaction on yourself so the flying person would get full body whiplash and if the lance hits something solid (shield) it would be like you holding a lance and charging into a cliff, It would HURT $\endgroup$
    – P.Lord
    Jul 7, 2018 at 14:09

I would consider the following:

More enclosed: If your developmental timeline permits it, copper for steep surfaces and slate for more level surfaces. A focus would be on steep rooftops so that dropped objects will fall to the ground rather than penetrate the structure. Coatings (e.g., rubberization or tar) might also be employed to protect surfaces from acids and other corrosives.

Protected Walkways: Where many of Earth's castles had an open space where all traffic, people and animal alike, traversed, I can imagine a focus on covered walkways, connected buildings, and even underground foot-traffic passages for everything but carts. (And maybe even some large ones for the carts.

Relocation: Earth's castles were often located because (a) the geography made them more defensible and/or (b) the location made observation of the surrounding countryside easier. In your case, I can imagine mountain sides such that only one side of the castle is easy to approach from the air. I can imagine taking advantage of natural caves. And I can imagine (b) not being an issue at all since flying troops would always be more efficient. Rather than locating near waterways, they would locate (perhaps) at altitude to minimize the number of attackers (or, said another way, to maximize the dependency on skill. Weak flyers can't easily reach the castle).

Central Towers: Where our castles tended to have narrow windows to maximize defense from arrows (and because glass was something that came later... large windows meant large drafts), I can imagine tower tops similar to helipads that permitted easy egress for stationed troops. Towers would be thick to accomodate the structure and to hold troops and supplies. Where our castles had (generally) some spires and high places for observation, your castle may have one or two cylindrical towers (basically a flat top, or some structure only on one side or dead center) about which the rest of the castle would be built.

Archers: Not knowing your technology level, I'm assuming that non-flying archers would find emplacement to protect against all but the highest-flying attackers. This might necessitate early development of smoked lenses (sunglasses) to protect archers against the sun as flying between sun and defenders would be an easy counter-attack.

Diminished Dependence on Walls: I'm guessing that having flying troops might cause less dependence on siege equipment. If so, sideways defense against incoming stones might give way to top defense against dropped items. Thus, your castles might not have a substantial surrounding wall (or it may be less prominent).

Avoidance & Detection: Finally, and I'm thinking about pidgeons here, your castles might develop roof spikes to keep unwanted guests from landing and weighted (if there isn't much snow) trip-pads where aerial attackers must land to enter a building that would activate an alarm (fancy way of saying, "ring a bell").

Searchlights: Finally, finally, I can easily imagine early development of basic mirrored optics. Think "searchlights" but with flares (brightly burning candles) vs. arc electricity. Of course, this would only be valuable if the searchlight can see the incoming attacker before the attacker is in range to destroy the searchlight... but it might be possible. Like I said... flares.

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  • $\begingroup$ When talking about Central Towers > Are you considering keeps/donjons ? $\endgroup$
    – dot_Sp0T
    Aug 19, 2017 at 17:57
  • $\begingroup$ No. Traditionally, keeps and donjons weren't tall enough to serve the purpose. However, the purpose of a keep/donjon could easily be combined with the tall towers I'm talking about. Limitations on materials and manpower tend to cause blended purposes. $\endgroup$
    – JBH
    Aug 19, 2017 at 17:59

What's your castle for? There are a few different reasonable answers:

1) Be imposing to look at and tower over the surrounding countryside.

2) Provide a secure strongpoint on a border.

3) Provide a refuge for people to flee to in the event of attack.

4) Somewhere for the rulers/rich to live.

(1) and (4) are the same as ever, except as (2) and (3) change things (although, if your ruling class happens to consist largely/entirely of reasonably strong flyers, their homes may be set up to be inaccessible except by reasonably strong flyers, to reduce how many people can get in).

Now, for the others, a lot has changed: for refuge during attacks (3), the correct answer, where possible, is basically "just bury it". It doesn't matter how well your attackers can fly (except for the ones that are going ridiculously quickly, I guess) if they need to attack down a narrow tunnel. If this is your only use, you're ending up with a tunnel system with only very defensible (and probably mostly hidden) entrances. You might want some farms above-ground, and those are going to be very hard to defend: they've got to be open to the air, just by their very nature. Honestly, I don't see a good way to defend this against a force with superior numbers in the air, unless you dedicate a large percentage of your population to just standing around there under some kind of protection shooting at those air forces. This might just be a matter of not having them, or giving up on them if the enemy has air superiority (therefore making air troops an essential element of any siege force that significantly shortens sieges).

For secure strongpoints (2), it's still mostly a matter of "just bury it", but you still need to have something sticking up above the surface, as a watch tower if nothing else. So basically a tunnel complex as above, plus some towers sticking up that have no entrances and just some narrow slits to look out (too small for anybody to get in through).

If we're adding imposing on countryside (1) in, pretty much as above, but make your sticky-up towers bigger and more imposing.

If we're adding grand residences (4), you might want a more significant above-ground complex (caves aren't that nice to live in). You still want it set up so that you can still get anywhere in the castle while staying underground except for right at the end, and certainly without going into the outside areas, and plenty of (well defended and easily sealed) entrances everywhere to let your rulers get underground in a hurry.

  • $\begingroup$ I edited your answer to improve the readibility. I have a terrible short term memory and was having trouble remembering the numbered reasons when scrolling down to the end of the answer. Feel free to undo if you don't agree. $\endgroup$ Aug 26, 2017 at 13:23

Well, if flying is a large issue in that world, one would probably imagine that they would try to build in places where up is protected, like building inside a mountain or underground, basically building in places where the flying enemy would be forced to stay low and close.


The question you need to ask is how big a rock can you drop how fast and how does that compare to siege weaponry? Is it possible to build a roof strong enough to stand such aerial bombardment for a whole siege?

Bear in mind that having flyers means that the besiegers are vulnerable to bombardment and to attacks on supply lines. Wrecking the supply karts of a moving army cripples its ability to move or to stay away from its supply source. Castles could be even more powerful, particularly if they can have launchers that give flyers an initial boost so flyers above the fortress don't have a big advantage.


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