In What would an age of sail flying ship look like?, my answer suggested ships that fly using 'keels' that utilise a difference in physics to that of our own world to achieve flight.

Now, I am trying to incorporate these flying ships into a setting similar to early 1800's Europe, around the time of the Napoleonic Wars, save that magic exists, similar to that depicted in Ars Magica 5 (warning: 20Mb PDF) save that magi operate openly, and are active at all levels of society.

The TL:DR of Ars Magica is effectively that magi can accomplish many things on a small scale over a limited timeframe, but large scale, long timeframe stuff gets difficult and expensive, and Magi comprise around only 0.05% of the population. There are simply not enough of them to go around. Most combat ships might have one, a ship-of-the-line would have one or perhaps two, and a flagship would have two or perhaps three. Fortresses might have several. However, Magi would effectively cancel each-other out in broad terms.

However, it has been pointed out to me that the fact that has historically allowed an empire to form is the effectively two-dimensional nature of warfare: since troops may only move en-masse on the surface of the world, in order to reach the heart of an empire, you must first fight your way across its' breadth.

Even today, that is true; despite having troop carrying aircraft, troops may still only be delivered to a battlefield in large quantities by surface transport.

However, with the existence of sailing ships with a potential armament similar to a ship of the line such as the 1808 HMS Caledonia, or the potential to carry an equipped body of 300-400 troops (where the largest modern troop-carrying aircraft can carry only around 100 equipped troops) and the ability to fly as high as it is humanly possible for the crew and passengers to breathe and continue to operate the ship, this means that it ought to be relatively easy to overfly the outskirts of an empire and aim a decapitating strike directly at the enemy capitol.

Historically, ships of the line were prevented from becoming unstoppable mobile fortresses by the simple fact that they could only sail where there was sufficient water, and that their wooden construction prevented them from using the best defence against them, namely heated shot, and additionally, the stone construction of the shore fortifications would have made heated shot less effective.

However, where ships may fly above land or sea, and can have considerable advantage in altitude, and where heated shot falling back to earth would pose more risk to the possessions of those firing it, flying ships would become unstoppable except by other similar ships. In such a circumstance, nations could be expected to be small and numerous, as the only effective defenses could be applied to small, localised structures.

So, my question: given the aforementioned changes to the technology of age-of-sail warfare, namely keels allowing flying ships, and Magi, how could empires be established?


To be clear, I am not looking to change the way these ships work, I am looking for innovations - preferably mundane, but if necessary they could be magical - that will prevent the indiscriminate overflight of a nation's sovereign territory, without having to have defence in depth.

To put it another way, I would like a way for nations to be able to establish an effective defensive perimeter, rather than having to blanket their entire area with defences.


Since it would appear that some are not reading the linked articles, I'll restate here how the keels work:

In this universe, Ether Theory has been proved: Ether is a universal medium through which everything passes. Most substances barely interact with the ether, but some interact more strongly, and some interact differentially, having low resistance when moved in one direction, but high resistance when moved in another, like a pipe moved through water. The amount of resistance that an object provides to movement is dependent upon its volume. A couple of cubic metres of keel would be enough to support a flying ship massing up to four thousand tons so that it would descend at a rate of a few metres per minute if it was not moving.

  • $\begingroup$ I think Napoleonic Era British Empire is a good example that it is workable; they defended themselves with their fleet, the forts were not needed and the army was used away from home. Just keep some of your ships at home ready for defense: assembly of an invasion force by an enemy is likely to be noticed so you can assemble your own forces for it/attack the concentration point. $\endgroup$ – SJuan76 Nov 2 '19 at 10:02
  • $\begingroup$ @SJuan76, defense by sea is a two-dimensional problem, where there is effectively only one degree of freedom (left and right). Air defence is a three-dimensional problem, and history has shown that it is very much harder to defend when there are two degrees of freedom (left/right and up/down)... consider the Battle of Britain during WWII. While during all of Britain's history as a major naval power, Britain has never been invaded by sea, during the Battle of Britain, German aircraft routinely penetrated Britain's air defenses... even when the British knew they were coming. $\endgroup$ – Monty Wild Nov 2 '19 at 10:51
  • $\begingroup$ A century later the UK did quite well against zeppelins, and yet some 30 years later it defended against a similar aerial attack... yes neither zeppelin nor Messerchsmith/Junkers are "air fortresses", but neither were the planes fighting them. $\endgroup$ – SJuan76 Nov 2 '19 at 12:25
  • $\begingroup$ Look up the Temeraire book series by Naomi Novik. Fascinating books set in a Napoleonic era where ship-sized dragons exist and are used in every country's army. She basically treats the airforce as an extension of the navy, using naval ranks and tactics, but supplemented with their own manoeuvring and signalling systems, anti-air guns that shoot pepper at dragon snouts, etc etc. Of course the main character is British so the naval angle is to be expected, but pick up the books anyway, for inspiration or for a good read. $\endgroup$ – KeizerHarm Nov 3 '19 at 15:42

You have a solution built in.

Your flying ships are far more restricted than you realize. A flying ship cannot sail into the wind, ships on water rely on the differential drag between the air and water to tack but if a flying ship tries this it just ends up sailing WITH the wind even faster. They may not even be able to sail perpendicular to the wind. so your ships can really only sailing in a roughly ~90 degree arch with the wind. This means if your countries map their prevailing winds they know where the ships have to come from, meaning they have to defend a much smaller area. Likely only a single border of hte country. In addition mountains which alter wind patterns will still act a barriers. countries can field their own ships with long anchor lines in defensive positions and they will be roughly as effective as ships of the line.

  • $\begingroup$ That doesn't make sense... they'd be no more limited in their ability to sail upwind than any seagoing ship, probably less so given that the keels don't allow very much leeway at all. They'd still have to tack or wear to cross the wind, but tacking could be dive-assisted, so even big, otherwise sluggishly-handling air ships could tack where a similar seagoing ship would have to wear. $\endgroup$ – Monty Wild Nov 2 '19 at 15:56
  • 1
    $\begingroup$ @MontyWild seagoing ships can sail into the wind because water has s much more drag than air, they are using the differential drag to get a net forward motion, without that differential it won't work, on a sky ship both planes are being hit by the same wind so there is no differential te exploit. If you are still having trouble this paper may help. atmosedu.com/Geol390/articles/Physics%20Of%20Sailing.pdf $\endgroup$ – John Nov 2 '19 at 21:34
  • $\begingroup$ John, you seem to have misunderstood the nature of the keels I described in my question: they provide a very significant differential drag, well in excess of that provided by water. They 'bite' into the ether, the fabric of reality, not air. Ether was disproved in our universe, but not in the universe of my question. $\endgroup$ – Monty Wild Nov 3 '19 at 7:49
  • 1
    $\begingroup$ @MontyWild in the future consider including a description of how your ships work in the actual question. $\endgroup$ – John Nov 3 '19 at 13:35
  • 1
    $\begingroup$ @MontyWild Please don't complain about an answerer not understanding the nature of your keels. Your question provides scant detail about their nature. Even your linked answer to the earlier flying ships question provides precocious little. 'A difference in physics" could mean almost anything. Basically this is a good question, but more background information is vital. $\endgroup$ – a4android Nov 3 '19 at 23:28

Suicide skiffs

Your keels, if I understand their fundamental operating properties correctly, can also be used as oars (in a smaller capacity) by fastening small ‘keels’ perpendicularly to a long wooden spar and using them to push off the aether on the backstroke, then turning and sliding them through the ether on the forestroke.

This means that a small, light skiff packed with gunpowder and featuring grappling hooks can happily be ‘rowed’ almost directly up to intercept any ship of the line travelling in a predictable wind driven path.

So your border defences are a series of forts packed with three man skiffs. Two men row like the blazes to put the skiff in the way of the larger enemy vessel, while another preps the ships weapons.

Now, if this were a regular battle the larger, faster ships of the line would simply blow past the skiffs, putting them in a stern chase and heading for the heart of your territory.

But this isn’t a regular battle for one good reason:

The ground is only hostile to the attackers.

Your skiffs are packed with greek fire and gunpowder and covered in grappling lines. All the defenders need to do is crash their skiff into the attacking ship, entangle themselves in the rigging, then light the fuses and bail out. Even one small, low crew skiff successfully detonating will bring the huge troop transport down to the ground where it will be quickly overwhelmed. The cheapness of the skiffs and the low crew requirements lets you make a veritable wall of death for any attackers, with swarms of suicidal skiffs mobbing and downing the larger troop transports. Unlike the open ocean your skiff sailors will return home heroes while the badly burned enemy will run into regiments of soldiers.

TLDR: Use skiffs as missiles.

  • $\begingroup$ Better still, keels can also be used as screws $\endgroup$ – Monty Wild Nov 4 '19 at 23:37
  • $\begingroup$ @MontyWild: yes... yes they can... hmm... $\endgroup$ – Joe Bloggs Nov 6 '19 at 21:30
  • $\begingroup$ The problem with this is the power source. Sailing ships have external power, but skiffs, whether oar or screw driven, have an internal power source, namely the crew. How many crew would it take to drive a skiff loaded with enough combustibles to be a threat fast enough to intercept a sailing ship - and to ascend to the correct altitude? If they're already at the correct altitude, how did they get there, and how can they stay there? $\endgroup$ – Monty Wild Nov 6 '19 at 22:55
  • $\begingroup$ @MontyWild: I was envisaging either constant running patrols skipping back and forth between forts (easy to do since your ships have such low crew requirements) or having the forts close enough together that an enemy ship can be spotted and interceptors launched in plenty of time (given that maximum altitude is much lower than maximum visibility). Probably a mix of both with flares for communication. $\endgroup$ – Joe Bloggs Nov 7 '19 at 14:14
  • $\begingroup$ @MontyWild: My original answer was going to be kite mines, so if we’re in an area of sufficient wind to let the big ship outpace the interceptors you can lift the interceptors with big ol ropes and wings. $\endgroup$ – Joe Bloggs Nov 7 '19 at 14:21

Firstly, restrict your flying ships to lower altitudes where ground-based forces can inflict enough damage to prevent their passage overhead. Possibly, as second but related suggestion: introduce flying dragons that can be trained to attack enemy flying ships of the line, into your world. Effectively this would constitute anti-aircraft or flying ship countermeasures to maintain territorial integrity and allow an empires to flourish.

Secondly, the keel material works best for small vessels. Cost of the keel material could be additional factor. The amount of keel material increases exponentially with the size of the flying ship. This could result in flying ships that require so much keel material incorporated into them, that there is almost nothing else but its keel.

Logistics. Napoleon opined an army marched on its stomach. if the carrying capacity of a flying ship was restricted, then any flying ship would have to live off the land during its flights. This is not dissimilar to maritime shipping in the Age of Sail, which regularly had to stop to reprovision themselves. This can be related to speed with which a flying ships can travel, maritime sailing ships weren't zippiest mode of transportation known. Slower flying ships will take longer to traverse territory.

Ports. As maritime vessels need ports to leave and go ashore. So flying ships might be only easily land and take-off from ground-based facilities. Consider the types of facilities required for airships and zeppelins.

While flying ships may be able to undertake "naval" action against major cities or even imperial capitols, they may not be able to land large numbers of assault forces.

The above suggestions, either singly or in combination, are intended to allow empires to flourish. They ensure large tracts of territory won't easily penetrated, or, at least, no easier, than they would have been by land forces during the Age of Sail itself, and certainly not before it. It is by finding various ways of maintaining territorial integrity and this will allow an empires to flourish. This should be similar in nature and kind to those that existed in the Europe of eighteenth and nineteenth centuries.

  • $\begingroup$ Given the way that the keels work, the only effective altitude restriction is the availability of oxygen for the crew. In theory, they could sail so high that the only limitation was the force the thin air could apply to the sails being less than the force required to maintain altitude... and then if you had alternative power, you could keep flying to the moon and beyond... This is how they work, so a 'Nerf everything' solution isn't ideal. $\endgroup$ – Monty Wild Nov 2 '19 at 8:24
  • $\begingroup$ As for ports... with landing gear and sufficient wind, they're unnecessary save for convenience... even today, for modern ships. $\endgroup$ – Monty Wild Nov 2 '19 at 8:26
  • $\begingroup$ Finally... a keel's load-bearing capacity is dependent upon its volume, while an aerofoil's capacity is dependent upon its planar area... so they actually favour larger ships. $\endgroup$ – Monty Wild Nov 2 '19 at 11:07
  • $\begingroup$ @MontyWild Given the way you didn't explain how the keels work, my suggestions remain reasonable ones considering they were made in an absence of useful information. Perhaps I should thank you for the edit to your question that makes my answer irrelevant. :) Do try to be clearer about essential details, in future. $\endgroup$ – a4android Nov 2 '19 at 12:15
  • $\begingroup$ @MontyWild I'd like to thank you. Considering your question led me to devise my own version of Age-of-Sail flying ships. I believe they are an improvement on some other flying ship concepts. I appreciate how you kick-started my thinking in this area. You have my gratitude. $\endgroup$ – a4android Nov 4 '19 at 5:36

Have you heard of Anti Air Weapons? These are weapons developed to attack flying targets.

According to the above link the earliest such weapons have been designed to a useful state around 1870ish. Considering that the use of aircraft (in this case balloons) in warfare dates to about the 1800s as a means of reconnaissance, we can easily assume that the development of anti air weapons would follow suit to the first use of your flying ships as assaultcraft.

The simplest designs seem to be built to saturate a 3D area with shells (the distance between shells needs only be a bit less than the smallest dimension of your flying ships), and/or to explode after a certain time which allows for an even larger spread.

On the role of troop transporters/landing craft: your comparison lacks an important understanding. The largest modern capacity of only about 100 equipped troops per plane is in no way comparable to an 1800ish equipped force. Napolean tactics relied on Line Infantry.

The smallest military units back around then being somewhere about 30-50 men. Comparing that to modern tactics, a platoon measures around the same amount of men, but said platoon is subdivided into 3-4 squads consisting of 3-4 individual fire teams which are acting mostly independent.

So by carrying 300-400 soldiers your ships would comparatively amount to about the same carrying efficiency, if not less (considering the need to supply this many troops behind enemy lines).

  • $\begingroup$ The trouble with anti-air weapons is that in the Age of Sail, the range of black-powder weapons was such that it would be very difficult or impossible to defend a border against high-altitude ships. Additionally, since Age of Sail ships could be heavily armoured, it would be very difficult to shoot them down with ground-based guns - to sink a combatant ship could take a considerable amount of time in combat, and a raiding ship is hardly going to hang around to get shot at by fixed defences. $\endgroup$ – Monty Wild Nov 3 '19 at 8:38
  • $\begingroup$ @MontyWild you don't defend the whole border. You defend strategic targets to prevent bombing/landing there. $\endgroup$ – dot_Sp0T Nov 3 '19 at 10:55
  • $\begingroup$ Have a look at e.g. Flak Towers - how hitler defended some cities. The principles apply even if the technology is a century earlier or two $\endgroup$ – dot_Sp0T Nov 3 '19 at 10:57
  • $\begingroup$ If u can't prevent the landing then force them to land at certain locations where you have the upper hand - that is anti air defense too $\endgroup$ – dot_Sp0T Nov 3 '19 at 10:57


Your point about the strength of a flying ship applies if the Empire is built using Medieval or Renaissance style cities. All the flying ship would have to do in that situation would be to stop above the city and drop large rocks until all buildings were reduced to rubble or a relief force of defensive ships arrived.

However, if the fixed settlements were primarily subterranean or built into cliffs it would be far more difficult to attack them effectively from above. Numerous secret entrances would have to be maintained to prevent the attacker from sealing the population in but this could be factored into construction. Ventilation and water supply would also be important for siege situations.

Naturally trade and agriculture would require access to the surface but the settlement could be treated as a 'keep' to be retreated to in case of attack while the surface was exploited during peacetime and between raids.

A flying fleet of one's own would be required to break sieges of subterranean fortresses and to deter attacks.


While most historical empires have eventually settled down to urban living a nomadic empire is possible and a number have existed. Since they would have no central point to attack it would be difficult for a flying ship to locate a point to bomb.

Further, even if the King/Khan/Leader's location was discovered, high mobility would allow a rapid retreat to the sort of terrain that would be difficult for flying ships to attack - caves, woodland, mountains etc.

A flying fleet would certainly help to deter attackers but conceivably a nomadic empire could hold some territory simply by virtue of mobility and avoiding concentration.

  • $\begingroup$ This still doesn't solve the problem I have... how to defend a border under these conditions. $\endgroup$ – Monty Wild Nov 3 '19 at 9:10

With three D dimensionality, the basic equations of warfare have been considerably complicated. No longer do you need to "punch through" enemy lines, but using air mobility to bypass the enemy, you unhinge their defences by landing in unexpected times and places.

This principle was understood as far back as World War One, when General "Billy" Mitchell proposed the idea of parachute dropped "Aero Infantry" or Soviet Marshal M.N. Tukhachevsky proposing "Desantnye" as part of the "Deep Battle" doctrine in the 1920's and 30's. In some regards, this is simply Cavalry raiding doctrine updated for the third dimension. In the modern era, the longest airdrop in history involved a battalion of US paratroopers jumping over Ukraine (on exercise) after an epic direct flight from the United States.

While parachute delivery of Infantry is fraught with danger and generally no longer possible against a peer opponent, under the conditions you propose it seems eminently doable (the parachute was described in the 1490's by Leonardo da Vinci, and modern replicas have worked very well indeed, being quite stable in flight). Tactical manoeuvre is also possible with airmobile troops, represented in the modern era by helicopter troop carriers and gunships. In this case the aim is to rapidly seize key terrain to support friendly movement and deny the enemy the use of this terrain.

enter image description here

Reproduction of Leonardo's parachute

enter image description here

Ju-52 dropping Fallschirmjäger

enter image description here

Soviet era troops exiting a Mi-35 Hind

The major issue with using airborne and airmobile troops is reinforcement and resupply. If the enemy is able to prevent the deployed troops from receiving reinforcement or supplies, then the outcome is quite terrible (for example the British Airborne Division at Arnhem, or the French Paratroopers at Dein Bein Phu). Even then, in the context of the larger effort, such deployments "may" draw sufficient enemy resources to change the outcomes of battles elsewhere (although this was certainly not true at Dien Bein Phu).

It does not require massive troop ships to deliver lots of soldiers, entire divisions were dropped in WWII using aircraft like the C-47 Dakota or Ju-52, and the modern example of a battalion of troops dropping in Ukraine used conventional transport planes to carry about 500 troops and their equipment. So even small "flying ships" can carry out airborne and airmobile operations, and savvy commanders can use airborne and airmobile operations to unhinge the defences and allow breakthrough operations with smaller numbers of troops moving at higher speeds.

  • $\begingroup$ I agree with all of this... but this doesn't answer the question: How to prevent it $\endgroup$ – Monty Wild Nov 3 '19 at 7:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.