After centuries of warfare, I imagine the art of castle design and defense got pretty advanced.
Is there a general consensus on “this particular castle” or “this particular style of castle” being the most defensible – barring prolonged sieges starving them out and before the age of cannons and firearms?
Are there any general rules to follow: always have a moat, never build one on a swamp, etc.?
And lastly, looking at them with the benefit of hindsight and modern science, is there anything medieval castle builders could’ve reasonably done differently that would’ve made defense even better?
Any of the castles built on an island, far enough from shore that siege weaponry couldn’t reach them, were probably pretty dang defensible in their day.
General rules: build on a hill, but make sure of a good water supply. Be near enough to trade routes to dominate them. (Germany has many beautiful old castles right on – or in – the Rhine river.) Maintain internal security; many castles were betrayed to the enemy. When your own guardsmen open the gates to the enemy, you’ve done something wrong!
Probably the best fortifications on earth, prior to gunpowder, were the walls of Constantinople. (Thread breaks into song…) Here is a nifty Wikipedia article. Scroll down just a bit to see a photo of a modern reconstruction of a section of the walls.
What? How do you move troop concentrations in and out of such a place? And couldn’t they load siege weapons on ships, where there’d be even less vulnerable to your defenses?
Not even. See the above mention of German castles on islands in the middle of the Rhine. You can dominate a vital trade route very easily by sitting right smack in the middle of it.
Reply - You couldn’t mount big enough seige engines on a boat to do any good. Recoil and all that.
On an island in a river where you can run chains across it and charge a toll for passage is one thing.
On an island not parked in the middle of a trade route is another. Plenty defensible, but plenty useless for controlling the surrounding territory too.
Istanbul was Constantinople
Now it’s Istanbul, not Constantinople
Been a long time gone, Constantinople
Why did Constantinople get the works?
That’s nobody’s business but the Turks
Prior to the invention of the cannon and given enough time to ready the defenses, many castles in the 14th century were effectively impregnable to direct assault. Siege engines could throw rocks at the walls for a long time before significantly affecting their defensibility. The approaches for frontal assaults could be limited and made very treacherous. Defense was just better than offense at the time.
Options:
Starve 'em out. Relies on having a large enough army to prevent access to the castle, the ability to supply such a large force and the defenders not having any friends nearby.
Undermine 'em. Potentially shorter than starvation if you can bring down a significant section of wall. Unfortunately, mining wasn’t as effective before gunpowder (and eventually TNT).
Bribe 'em. As others said, getting someone on the inside to help you is the best way.
Hohensalzburg looks like a good bet. It was only attacked once without success, and was given over to French forces in the Napoleonic War without a fight. I’ve seen this thing up close, and it’s formidable.
Depends what the purpose is. For defending the country against foreign invaders, it may not be any good. For protecting the local baron against potentially rebellious peasants, it’s fine.
One of the prettiest castles ever, to be sure… But not defensible. The walls aren’t thick; they’re shell-thin. The place is every bit the “Disneyland” it inspired. You might as well hole up in Blenheim Palace.
Good heavens. That looks like it’d be a bitch to capture even with modern weaponry.
‘Most defensible design’ really depends a lot on era and context and intended purpose. As a couple of people have pointed out, island castles are very defensible, but not terribly useful. The attacking army can leave a small number of troops guarding the ford and send everyone else on to the really valuable targets. If the castle doesn’t have a good supply of fresh water, it may starve out very quickly. It’s a great example of winning the battle but losing the war. If you’re looking for the castle that makes military historians go weak in the knees, I have no idea what that would be.
I don’t have anything of major interest to contribute, but as for general considerations when building a castle, sure there are several.
High ground is of obvious advantage.
Concentric walls are good. The outer area can be abandoned and attackers have another nut to crack.
Fortify a harbor. This allows another route for resupply.
Yes, moats are a good idea. They effectively make the wall taller but lowering the surrounds. They also make it harder to mine under the walls.
Improvements with hindsight? Maybe barbed wire could have been added to medieval obstacles-- it seems like a simple enough invention. Possibly the star fort design, which came about in response to gunpowder. This is a pretty major case of hindsight, but it could have extended the life time of medieval fortifications. However, fortifications are extremely expensive and using later designs probably wouldn’t have been more effective than medieval ones.
