Edit: This question has been reopened!

Medieval castles are mostly designed towards delaying or obstructing ground attackers. The only real threat a castle faces from above, at least from humans, comes from arrows volley fired up towards the battlements and arcing downwards or siege equipment. These threats are negligible if a castle is placed high enough, but for air attacks this isn't necessarily the case. Technology is around the mid-medieval era with the inclusion of fantasy races. It would be best if the castle's fortifications still retained most of their potency against ground threats as originally intended, as ground forces remain the most numerous in world with air units usually reserved in an auxiliary or decisive shock role due to their relative scarcity.

I've decided to group threats into two basic archetypes:

  1. Airborne Skirmishers: riders on the backs of flying monsters such as a griffon or wyvern, or monsters themselves like gargoyles use ranged attacks to suppress or kill the castle garrison. Carrying stones and dropping them, javelins, archery, incendiary projectiles, etc would fall under this category.
  2. Melee Assault: melee attackers are inserted onto the defenses via airborne mobility. This would cover riders dropped off onto the battlements or beasts capable of melee attack themselves. Swooping attacks also fall here. Their goal, besides killing garrison troops would be to disrupt ranged defender fire and taking strategic points such as a gatehouse.

Against either threat a standard crenelated castle battlement would have little to no effect. Crenels and merlons only provide horizontal protection. Gatehouses and moats would similarly have no effect. Garrison troops on the wall would have a tough time against skirmishers, and only limited defense against melee attacks. Spears, the most common militia weapon due to ease to use, low cost, and long range aren't so good on walls. They are best in large tight overlapping formations hard to form on thin battlement walkways, and if formed make easy targets for air skirmishers. Bow users are precious with how long it takes to train a proper archer to properly use warbow draw strength. Losing them to melee assaults that get through their arrow fire is suboptimal. Mixing archers and melee garrison forces on the walls might cripple both parties, as spears and bows need free space to maneuver. The battlements on walls that would help them against ground attacks basically ties the garrison's hands against air attack. They need proper defenses to give them a defensive advantage against all attackers.

My first thought was wooden hoardings, or temporary wooden framed extensions built around rampart or parapet battlements. These usually included arrow loops for returning fire on besieging forces, but only horizontally. The roofs were usually solid to provide better arrow protection and sometimes covered in rawhide to counter incendiary attacks. A solid roof, while protecting best against ranged skirmishers also keeps defenders from firing up at them, ceding the sky. They would also just provide good landing spots for melee assaults, who could just land on them safely and rip through to get down to the garrison underneath. Possible solutions include adding wooden spikes on top or opening arrow loops upwards, but both have downsides. Namely increased weight and increased fire chance from wooden spikes, while arrow loops weaken the original purpose of protection against missiles.

My second thought would be to place matching height towers in pairs with their roofs sealed off and gently sloped towards each other. By firing through arrow loops/slits across at each other, the tower pairs could cover each other's roofs versus melee assaults. With the only openings underground or arrow loops, there would be no easy access into the towers from the air. If the arrow slits are above the hoarded battlements, they would also be able to fire down safely on airborne melee assaults trying to go down through the hoardings. This is a rather costly solution, effectively requiring double the flanking towers and obscures wall line of sight towards ground targets at the base of the wall which isn't a big problem with single towers.

The last idea I had would be to give up castles altogether and go full underground bunker. This is a bit extreme, but would force a ground invasion. Naturally this isn't a very pleasing option for matters of prestige, one of the main administrative duties of a castle. It would also be only subpar versus land assaults, being vulnerable to tunneling efforts and flooding in most terrain.

Any ideas or suggestions?

  • $\begingroup$ I'm wondering if the airborne soldiers would attack the battlements at all. If the enemy has spears or arrows, the air mounted warriors are very vulnerable and visible. One good hit on their mount and they're likely down. They would sooner drop (fire)bombs on supplies or wooden targets from high above, pelt the enemy in the courtyard with stones or arrows, or land at a safe place to offload the warriors, then return. It can be used in surprise from behind or the like, but in general they would probably stay far away from danger and do ranged attacks. $\endgroup$
    – Trioxidane
    May 20, 2021 at 9:40
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    $\begingroup$ I recall a Youtube video from castle enthusiast Shadiversity on how to fortify a castle against dragons, which presents similar challenges. Long story short, fortifications are useless. Get yourself tons of heavy artillery and crossbowmen. $\endgroup$ May 20, 2021 at 11:27
  • $\begingroup$ Dragons arent really the same as a gryphon or wywern. Its like comparing a nuke to a 500lb bomb. Sure, a concrete bunker is useless against a nuke, but it does a great job vs a 500lb bomb. $\endgroup$ May 20, 2021 at 11:30
  • $\begingroup$ Does your world have magic? If yes, then what kind of war magic do you have? What kind of attacks flying monsters have? Are they magic attacks like projectiles or they are physical attacks with claws? Also, do you have Greek fire or any other burnable substance that can be used in flamethrowers or grenades and is hard to extinguish? $\endgroup$
    – Otkin
    May 21, 2021 at 1:52
  • $\begingroup$ I removed magic from the question to focus discussion. It exists, but not enough capacity to sway a field battle in a meaningful way besides decapitation or guerilla strikes. At most a fantasy creature seen deployed in wars is a bit sturdier than a mundane creature. All normal weaponry from the medieval and past are applicable, greek fire, tar, etc. $\endgroup$
    – yolo man
    May 21, 2021 at 9:21

5 Answers 5


Nets and chains

You'll still need conventional fortifications (castle walls, towers moats and ditches etc) because no matter what defenses you might build to prevent 'attacks from above' your enemies can still simply just land outside your castle/town' and attack it at ground level.

That said a Castle could potentially shield itself from airborne assaults by stringing a series of chain and/or wire reinforced ropes and nets (with blades or hooks added as a bonus?) across the open space between towers. (Note: I'm presuming the mounts of the attackers e.g. griffins etc can't 'hover' for any length of time - they're not helicopters after all. Animals that's size carrying an armed and armored rider would have the choice of flying or landing but not hovering.)

The important thing is that these 'nets' don't have to be 'meshed' in the same manner as conventional fishing nets. The animals your trying to hinder would have 10-15 meter wingspans so your mesh can be 3 meters wide or more and still be narrow enough to prevent the mount from landing. And of course a net with that kind of spacing will not hinder your troops archery (much) as they fire back.

Adding fire/smoke pits/cauldrons at strategic points would help too. The smoke and heat might tend to cause the mounts to swerve away.

For towns you can;

A) have steeply slanted roofs that prevent anyone landing on top of them; and
B) streets designed so they are narrower than the wingspan of the mount used and that twist and turn in a manner designed to leave no landing points other than places like public squares etc that you can net or alternately turn into killing grounds with overlapping fields of fire etc if foes do try to land there.

  • $\begingroup$ How would one string the chains and ropes nets up? Would you attach two ropes at the two endpoints and throw the lines down for someone to run over and connect in the middle? That would take a bunch of extra rope for the slack but should work. Also, what happens if the enemy decides to go after the mooring points first? $\endgroup$
    – yolo man
    May 22, 2021 at 5:41
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    $\begingroup$ The simplest way would be to consider them part of the normal defenses of a castle like walls or towers so once erected they could be left in place more or less permanently. (With sections only being taken down for repair or maintenance as required). So when first installed a series of heavy 'lead' ropes could be dropped to the ground from once section of wall or tower, dragged across any open space by teams of men to the next tower/high point before being tied off to other ropes and then pulled up into place & secured by another team. The 'net' would be cross ropes attached to the leads. $\endgroup$
    – Mon
    May 22, 2021 at 7:22
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    $\begingroup$ Part 2; The point is one giant net covering the entire castle etc even if practicable (which is unlikely) isn't required or even desirable. If only because damage or wear to any one section would require the entire net be taken down! So the best idea is to use multiple nets hung in a 'checkerboard' fashion so that all the Castle is covered but any one piece can be removed and replaced as needed. Remember this 'net' is made with 3-5 meter gaps from strong chains or if possible steel wire reinforced ropes so you want it to stay in place as long as possible. $\endgroup$
    – Mon
    May 22, 2021 at 7:33

The first solution for most of your forces is roofs over their heads.

The second solution is to shoot them down. As early warplanes already proved it is exceedingly hard to hit a target from an aircraft. Early WWI designs dropped metal darts, but an entire box of metal darts had to be dropped on large groups of enemies to even score a single hit. If you have archers with the ability to accurately hit enemies from the unstable position of a flying beast, then those same archers on the ground would be much more effective shooting those aerial targets down.

The third solution is to smoke them out. Build chimneys that spew out thick and debilitating smoke when you are attacked, this obscures targets for them (this even worked during Desert Storm against jet fighters!) And flyers that go through it could become disoriented or disabled in flight, if not blinded as soot builds up on their eyes.

The last solution is nets and cables. You aren't talking about woodland fliers but large relatively ungainly creatures. Using the WWI and WWII tactic of lines attached to balloons near potential targets to give them the risk of hitting one ans crashing. Nets can similarly be hung between towers or across open spaces where fliers might try to land so they get caught in the nets instead.

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    $\begingroup$ archers on the ground should have better accuracy as you say but the airborne ones should have better range given they presumebly have both height and speed on their side $\endgroup$
    – jk.
    May 20, 2021 at 13:15
  • $\begingroup$ @jk I know what you mean. However more height and speed would increase inaccuracy. Having to fire 100+arrows for a single hit against large formations might not be the way to go, and especially fortifications don't have large formations out in the open. $\endgroup$
    – Demigan
    May 21, 2021 at 2:43
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    $\begingroup$ Firing a lot of arrows to kill some of an already small garrison is probably a good thing. That said, a single hit out of 100+ arrows seems a bit exaggerated. Horses at full gallop aren't particularly stable, but horse archers or chariot archers could hit targets reasonably well. Birds and other flying creatures are much more graceful, mostly because they don't need to push off of the rough ground at rapid intervals. A flyer in a circle or banking turn would be especially stable as most avian creatures don't flap during turns at all. $\endgroup$
    – yolo man
    May 21, 2021 at 8:17

Dwarven Cliff Fortresses

The only fortress that is impervious against airborne attacks is a dwarven cliff fortress. It is built into the steep cliff of the mountainside, the only entry to it is a gate in the center of the wall - with thousands of slim arrow slots and gunports allowing to turn the bare rock field with strategically placed road marks (read: range marks) an approach that is deadly to all foot soldiers.

The very design of the fortress carved out of the mountain prevents any airborne unit to attack anything directly: there are no exposed walkways, the solid grown rock of the mountain can withstand the landing of any dragon and ripping out a piece of solid granite from the wall to get into the castle there is near impossible for an airborne fighter.

The natural shape of mountains only leaves one attack vector for the airborne fighters: towards the wall, from where arrows, bolts, and bullets will pour and shoot them down.

Dwarven hill fortresses

In areas where no natural rock is available, the dwarves will use casted rock (aka cement) with iron reinforcement grids in them. The resulting constructions look like small rock outcroppings with domed tops, the area in front of them kept barren. Often these artificial outcroppings are put on top of retainment walls of several dozen feet height to make them inaccessible to footsoldiers.

The downside is, that the hill fortresses actually have a top that could be landed on, requiring the outcrops to have overlapping firing cones.

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    $\begingroup$ I always thought it was silly that Erebor fell to a dragon... like of all the possible places Smaug could have chosen to attack, that was the one place that reasonably should have been able to defend itself. $\endgroup$
    – Nosajimiki
    May 21, 2021 at 14:20

There are many ways to protect your castle against aerial threats while keeping the standard crenalated beauty looking properly medieval.

  1. Roof mounted bolt throwing ballistae on a central tower that overlooks the walls. Aerial skirmishers need to fly and flying requires a low weight load on the beast. Your skirmishers will likely be minimally armored so they can carry plenty of rocks/javelins to harass the battlements as well. A plate armored gryphon might not even be able to fly. This is a well known fact to your defenders, so they use extra light bolts in their ballistae. The bolts have incredible range thanks to their velocity and will down any skirmisher in a single hit. Birds use muscles in their wings, shoulders, back and chest to fly. Any bolt that pierces these muscles (the majority of their body) will drop the flying beast like a stone. Imagine getting shot in the leg by an arrow: you wont be running anywhere.

  2. Airborne skirmishers. If the attacking enemy has them then you should too. Just engage the enemy and they cant harass yiur castle.

  3. Trained attack birds. A horde of pigeons, or hawks would disrupt the attackers enough to make them less effective.

Melee assault is easier to deal with than skirmishers because the gryphon carrying soldiers needs to land for several seconds to offload their cargo. During that time they are incredibky vulnerable to attack. As I said above, a single arrow piercing their armor would cripple their ability to fly. How expensive are those gryphon? Are they worth it to put 2 men on the walls? My guess is no. I really doubt aerial assault is a valid tactic here. Especially when the walls will be bristling with defenders.

The way your army should be using their flying assets is during a direct ground assault to sew panic and confusion on the walls. Skirmishers should only risk their lives and their mount's life during such assaults. They will target perceived weak points with their aerial bombardment while trying to dodge ballistae fire. Things will get messy, but maybe if they kill a few defenders then the way can be opened for the ground troops to scale ladders.

When your army isnt assault castles, a far better use for aerial cavalry is harassing the enemy's supply train. If they really can carry multiple riders then all the better. Your aerial dragoons fly around and find enemy wagons, stealthily dismount nearby, tie up their precious ride home, and finally go reave the caravans before returning to camp.

  • $\begingroup$ I've considered ballistae, but they don't seem very cost effective. They require quality sometimes metal parts and engineering. Ballistae have very slow rate of fire and tracking speeds. They are essentially the smallest siege weapon available, and siege weapons were always limited in number. They were no anti-aircraft guns capable of being trained quickly and precisely on moving targets. Fast moving swivels would be hard without metal and machinery, much less precise. Even if they could be aimed, they would get maybe one or two salvos in before getting attacked. And they would get hit first. $\endgroup$
    – yolo man
    May 21, 2021 at 8:28
  • $\begingroup$ You should have specified that your world is low metal and does not have medieval levels of engineering. I assumed such because you have crenelated castles which implies a certain time and tech level. Ballista are pretty simple the romans used them for field battles as the first field artillery pieces. They were accurate (picking out targets at hundreds of yards away) and had a suprisingly high rate of fire (more than a hand loaded crossbow with a trained crew) Look up Roman Scorpio. They can be built entirely of wood fyi. $\endgroup$ May 21, 2021 at 8:35
  • $\begingroup$ Scorpios are reported to have been powerful enough to (in one case) go through a man's shield, his armor, his body, and then pin him to a tree. They had pinpoint accuracy to more than 100 meters. If you reduce the weight of the bolt it increases the velocity and the range of pinpoint accuracy. Your enemy will definitely be coming within 100 meters if they want to accurately throw javelins/rocks from gryphon-back. Maybe they discovered that it is best to dive bomb your targets which makes them even easier to hit. The greeks built a repeating one called polyboros. That was in 280bc $\endgroup$ May 21, 2021 at 8:41
  • $\begingroup$ It isn't that the world is low metal or engineering, rather the designs of ballista are not like video games where they sit on a rotating swivel or turret. Most ancient ballistae are solid frame from top to ground. Most either have to be lifted and turned or use small wooden wheels on the back feet and wheeled that way, usually requiring more than one gunner. While very accurate, it takes a lot of time to train a ballista on target, and makes tracking moving targets near impossible. Ballista have to be secured (immobilized) before firing to manage the recoil. $\endgroup$
    – yolo man
    May 22, 2021 at 3:44
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    $\begingroup$ I believe you are envisioning the siege sized ballista. Im talking about scorpion sized ones, which the romans actually had on swivels. They used them in field battles to snipe cavalry among other enemies. They had a crew of 2 and shot a bolt every 10 to 15 seconds. They were about 5 feet in length, so not some lumbering engine. en.m.wikipedia.org/wiki/Scorpio_(weapon) $\endgroup$ May 22, 2021 at 8:20

For big fliers: medieval flak guns. Make large ballistae with very wide flight grooves and fire panes of glass or ceramic at dragons, wyverns, and others. For smaller ones, such as gargoyles: net launchers. Make some sort of contraption to fire razor-wire nets with weights on their ends. They will wrap around the enemy, both ensnaring and lacerating them. For protecting your garrison, roofs or holes-in-the-wall would be best. Also, cover the roofs with acid or something else painful to keep ground attackers from landing.


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