Despite being awesome marvels and once incredibly important, ever since explosives became a thing, castles have become obsolete. Until now...

Imagine two equally advanced civilizations at war. Both factions feel as if castles make great forts in that day of age (futuristic scifi).

These castles externally appear as if they are medieval castles but are also armed with higher degrees of defense mechanisms such as force fields and anti-aircraft turrets. They use the castles to hold weaponry and supplies, house troops, and to hold strategic defensive locations.

The civilizations don't use exclusively castles but I would say that about 33% of each faction's forts are castles.

Why would civilizations with advanced technology (think Star Wars-like technology) even consider using castles as forts?

  • $\begingroup$ The new Voltron series has an advanced civilization with a castle, but the castle also turns into a spaceship. You might want your castles to be mobile! $\endgroup$ – skeletim Sep 20 '16 at 14:26
  • $\begingroup$ I don't know whether you'd consider Britain to be an advanced civilization or not, but Windsor Castle (among others) has been in use since shortly after 1066. $\endgroup$ – jamesqf Dec 6 '18 at 5:17

Advanced civilizations would find something like a castle useful for the same reasons that civilizations have always found fortresses and castles of various types useful; Because the combination of materials technology and defensive architecture available at that time can overcome the ability of weapons to deal damage to a protected target.

If we think about a future civilization with FTL technology (you mentioned "star wars"), we can easily postulate that they would have developed some extraordinary materials technology in order to have an FTL ship that could withstand the stresses and impacts it is likely to see during normal operation.

Development of some material strong enough to handle the abuse that FTL travel would probably dish out would radically alter the offensive/defensive paradigm. We could assume that if a ship can be built out of Superstuff, then why not a fortress?

We would have to figure that the combination of architecture and materials would be enough to resist/defeat a nuclear strike AND orbital bombardment with something like "god rods". That means we are talking about materials so strong that even if the part of the planet underneath the fortress were vaporized by an asteroid, it would largely be intact. That means the fortress would have most of the characteristics of an FTL ship but probably just lack the drive itself.

This could be something that they find useful because of the expense of the drives and the value of whatever other resources are on the planets. We can compare this to the way that castles served as a point from which small armies could "sortie" out against an enemy. Even if the rest of the planet is vulnerable to orbital bombardment, the fortress would be able to cause a lot of damage to attackers while they were within close enough range to attack.

Strategically, this might look like the Napoleonic naval war era, where ships were basically floating artillery platforms, but they always had to worry about the superior guns that could be placed on an enemy fort, and forts were built to cover the entrances of strategically important harbors.

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    $\begingroup$ Materials technology is a featured plot device in the alternate history Castle Wolfenstein series. In the backstory of the series, the Nazis developed an "Über-concrete", which allowed them to quickly construct highly resistant fortifications. $\endgroup$ – Kys Sep 19 '16 at 20:21
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    $\begingroup$ A point about Age of Sail era gunnery: while the ships had smaller guns, they generally had an advantage over forts in firepower due to accuracy, for two reasons. One, the ship was moving and the fort was not, and when you are shooting based on eyeballing it an moving the cannon with ropes, that can be a big difference. Two, The ship could move to bring all its guns into a broadside together, while the fort couldn't. If the ship sailed past the fort's gunport, the fort couldn't do anything. As late as the Civil War, Union naval vessels routinely used this advantage to reduce Confederate forts. $\endgroup$ – kingledion Sep 21 '16 at 0:31

It's not the technology level which makes castles valuable or worthless, it's the differential between the value of being able to hold still, defending a spot of land, and the ability of the attacker to bring offensive weaponry to bear against said emplacement.

Castles were very effective in their era because the kings of the day could afford to spend an inordinate amount of labor building structures that were virtually impenetrable to any weapon of the day. The invention of siege weapons changed the balance a bit, but it was still plausible to build a castle so strong that no siege weapon could take it down. This balance was destroyed with the invention of the cannon. No stone structure could withstand the beating that a cannon unleashed on it.

The key to this is the sense of time. A king could spend decades building his castle and strengthening it against attackers. Attackers, limited by the mobility of offensive weapons at the time, were unable to keep up. There was also a strong sense of desire to stay in one place. A king did not want to move from his castle, so once it was up, the king could just stay there.

So those are the keys to having scifi castles:

  • A reason for powerful people to want to stay in one place for a long period of time.
  • The ability to shrug off any siege weaponry which could be brought to bear.

The latter is the one which is hardest. Modern combat has found many ways to deal with a foe that is willing to hunker down like this. We're so good at destroying things these days, that the most effective combatants are those which are always on the move. That way you can never bring to bear our particularly powerful weapons on them. However, if your technology is shifted such that this is no longer the case, castles could become a thing again.

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    $\begingroup$ Medieval armies had another time limitation: Most peasants only owed a certain number of days of service to their lord per year. (40 days per year was common.) $\endgroup$ – Jasper Jul 25 '18 at 6:25

Some thoughts:

  1. The materials used to construct the buildings could be comparably advanced and resistant to the weapons of the period.

  2. Similarly, there could be some inherent trait about their weapons technology that makes a certain natural mineral or material resistant to it, so that material is used in their constructions.

  3. There could be symbolic reasons for wanting to have your bases appear certain ways. For instance, perhaps there's a cultural motivation to invoke some historical location or imagery.

  4. Depending on the exact nature of their approach to warfare it may actually be advantageous to have a structure like a castle for defense. For example if conflicts largely revolve around ground-based attacks and foot soldiers, it might make a lot of practical sense. Or maybe battles take place entirely in caves. Or perhaps something in the atmosphere hinders their ability for aerial-based combat. Etc.

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    $\begingroup$ Cultural I agree: If they originate from, say, Earth and are now living on a different planet (or in a different time) then they may simply want to replicate castles for purely aesthetic reasons. The interiors of course have all mod cons and the exteriors are protected by force-fields but the look of their homes is still important to any powerful ruling class. $\endgroup$ – chasly from UK Dec 5 '18 at 20:36

Castles, like any fortification, are designed to project power over an area and at the same time resist being taken over. What makes a castle different from a "base" or "bunker" or other fortification is crenelations, arrow slits, moats, double gated archways. These are all things designed to protect counterattackers and make it really hard for ground-based troops to enter.

You said these castles have force-fields and anti-air defenses (anti-ship, missile, energy beam, god-rod, etc.). Well, once it's clear that air assault will not work, an attacking commander may well switch to ground-assault.

It may be that force fields can deflect an energy beam, but maybe they can't stop a physical slow moving object (like a foot-soldier). So, perhaps high-tech weapons have cancelled each other out enough that old-school D-Day style frontal assault is the only choice.

And what would be really handy when you've got thousands of armed troops running at you? Crenelations, arrow slits, moats, and gates.

In reality, though, I would think a CIWS would take care of just about anyone coming at you. And those things are scary automated. So, to be fair I guess the foot-soldiers would have to have some pretty good armor. Totally doable.


They don't have gunpowder.

In an Alternate History Hub video about gunpowder, or the lack there of, he points out that without gunpowder for bombs and cannons, walls around a city is still a good strategy.

You can still have your world have advanced knowledge of chemistry, physics, medicine and mathematics. The can have democracies and vehicles, but without gunpowder to make things go boom, walled cities (basically a large castle) are still a great defensive strategy.

  • $\begingroup$ Even before modern warfare, I think there were already multiple types of explosives known to scholars. And now, because of physics and chemistry, we have lots of other things that go boom besides gunpowder. Even beyond our 100 flavors of conventional things that go boom, we now also have nukes. And this question is about advanced technology, so we should also consider antimatter explosives since that is something we have the technology for even today; any author's futuristic society could easily have antimatter factories making military-sized quantities of it. $\endgroup$ – Loduwijk Aug 18 '17 at 17:58
  • $\begingroup$ Another issue here that explosives are not the only thing that destroyed castle walls. Flinging boulders at walls was a good way to bring down many of them, which they did with catapults, trebuchets, and the like. These days, even if the military had no explosives, we would probably have awesome 10-ton-boulder-flinging machines. Gunpowder is not the only modern way to send objects flying; we also have things like hydraulics, rail-guns, and more. Please note: Your answer is still very valid, and walls are still good; just don't underestimate our ability to wreck them with more than gunpowder. $\endgroup$ – Loduwijk Aug 18 '17 at 18:04

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