Got a Real World Weapons or Armour Question? Mk XII

[fusilier]

Now based on historic accounts, how much more would the monthly "rent" for a unit of mercenaries be, compared to the monthly "maintainance costs" of having a standing army unit of comparable "combat power" (how much use they are in battle). Now, standing armies have not been that common during history, from what I know, but what would you say would be a good monthly cost for hiring a mercenary unit? Three times the cost for standing troops? Four times?

From knowledge of 15th century Italian "condottieri" contracts, the difference per soldier wouldn't actually be that much. The main differences would be the various perks that were delivered to secure the services of the captain. These were often hidden, and not standard.

The standard additional pay, over the norm for just the lance, included the caposoldo which was one additional ducat per lance (a lance being paid between 8-15 ducats/florins a month). The caposoldo was to help pay the junior officers of the company, which weren't usually given a lump sum in the contract (so it's something that a standing army would also have to pay). The other common "extra pay" was the paga morta, similar to an English Blynde Speare, it was pay for lances that didn't actually exist. This proportion could vary and seems to have been seldom fixed (I thought I had read an extra 10% somewhere, but I'm not finding that at the moment).

A provisione could also be specified for a senior captain; it was a lump sum payment that was to go directly to him. The point of most of these extra pay was to handle the overhead costs of running a company.

Permanent troops were also employed in Italy at this time. They would be paid and employed directly by the state, but the rates were basically the same as the mercenaries. The state would save a little in overhead, but probably not much. Primarily, they gained a bit more stability, and the ability to retain troops that they thought were valuable, even if their mercenary leader had passed away.

[Spiryt]

It was only something that I vaguely remember reading -- I was hoping that someone else would remember it better than me. :-)

Anyway, Payne-Gallaway was using a heavy siege style crossbow for those tests.

For comparison, the maximum range of longbows has been estimated at 400 yards (a reproduction of one from the Mary Rose reached about 360 yards), and for a turkish bow, I've heard estimates of a range of about 500 yards. That's absolute maximum -- NOT effective range. [W.F. Paterson believes that a turkish bow, with an experience archer on a good day, could hit a target the size of a man on horseback about 1 in 4 times at 280 yards]

Given the differences in force applied (although, there are probably some other factors involved too), the ranges of arrows launched from bows seem pretty impressive compared to crossbows. Which implies, to me, that arrows were more aerodynamic than bolts (and probably more stable in flight).

Actually, record Turks archery records are believed to be well beyond 800 yards, and modern attempts seem to confirm it.

Such flight shooting is only sport, obviously.

But the point is that your premise that force applied has any direct connection with arrow range is misleading.

Most important thing as far as range goes, is obviously velocity. Any (cross)bow can only send missile as fast, and any additional energy will go to waste, if projectile mass won't change.

So more energy can be used by sending heavier missile fly at roughly same velocity.

So Payne Gallway using heavy crossbow doesn't in any way imply that arrows are 'more aerodynamic'.

Very heavy bolts would have better cross section to mass ratio, so would fly further at given velocity, but that's not that big gain.

[fusilier]

Actually, record Turks archery records are believed to be well beyond 800 yards, and modern attempts seem to confirm it.

Such flight shooting is only sport, obviously.

But the point is that your premise that force applied has any direct connection with arrow range is misleading.

Most important thing as far as range goes, is obviously velocity. Any (cross)bow can only send missile as fast, and any additional energy will go to waste, if projectile mass won't change.

So more energy can be used by sending heavier missile fly at roughly same velocity.

So Payne Gallway using heavy crossbow doesn't in any way imply that arrows are 'more aerodynamic'.

Very heavy bolts would have better cross section to mass ratio, so would fly further at given velocity, but that's not that big gain.

Ok I think I see what you are saying.* What I challenge is the assumption that crossbow bolts all have better cross section to mass ratio. Something like a ballista bolt -- I wouldn't doubt. Those could be very big. But crossbow bolts, seem to have generally been thick and short. Whereas an arrow could be very long and narrow.

As Galloglaich points out there are many different types of crossbow bolts, and how they were used, and which were used with particular types of crossbows is still unknown.


*Getting back to the physics:

Are you claiming that an arrow from a longbow is propelled with greater velocity than a bolt from a heavy crossbow? (The only stats that I can find show them being about the same ~55 m/sec, but I'm not sure if I can trust them).

--EDIT--
Just stumbled across this webpage:
http://www.thebeckoning.com/medieval...oss_l_v_c.html

It claims that bolts were typically lighter than arrows (significantly so). So that an arrow would certainly have a better mass to cross-section ratio! At anyrate, there seems to be a lot of contradictory data out there. ;-)

[Avilan the Grey]

It claims that bolts were typically lighter than arrows (significantly so). So that an arrow would certainly have a better mass to cross-section ratio! At anyrate, there seems to be a lot of contradictory data out there. ;-)

Indeed. As I understand it bolts are lighter, but has a higher "mussle" velocity than arrows.

[Spiryt]

Ok I think I see what you are saying.* What I challenge is the assumption that crossbow bolts all have better cross section to mass ratio. Something like a ballista bolt -- I wouldn't doubt. Those could be very big. But crossbow bolts, seem to have generally been thick and short. Whereas an arrow could be very long and narrow.

Uh, no all I was saying that Payne Gallaway was shooting heavy crossbow, with heavy bolts.

Heavier bolts, will have, comparatively, better flight characteristics than light ones.

Are you claiming that an arrow from a longbow is propelled with greater velocity than a bolt from a heavy crossbow? (The only stats that I can find show them being about the same ~55 m/sec, but I'm not sure if I can trust them).

--EDIT--
Just stumbled across this webpage:
http://www.thebeckoning.com/medieval...oss_l_v_c.html

It claims that bolts were typically lighter than arrows (significantly so). So that an arrow would certainly have a better mass to cross-section ratio! At anyrate, there seems to be a lot of contradictory data out there. ;-)

They don't claim that bolts were typically lighter, they just quote someone who used very light bolt for rather hefty crossbow.

There's no actual data here.

Experiment doesn't have any real details either.

All I can see that someone had used very heavy arrow for bow draw - about 16 grains per pound of draw, so achieved rather sluggish 40 m/s.

And achieved similarly sluggish result with crossbow with very light bolt, so probably something was low grade here, because results are very poor.

Are you claiming that an arrow from a longbow is propelled with greater velocity than a bolt from a heavy crossbow?

Well, no, nowhere did I claim something like that.

55 m/s is fairly typical for traditional bows and crossbow alike.

Exact performance depends on many things, beyond just 'longbow' and 'crossbow'.

Generally though, I think that crossbows could be pretty fast, because short lenght and thus pretty short distances to cover for arms, string etc. As far as maximal velocity goes.

Here those guys actually made somehow scientific experiments.

Their crossbows doesn't seem particularly successful, they admit that they don't really know enough sources, they quickly took significant set.

But they still achieved rather respectable 61 m/s or 200 feet/s.

[Knaight]

Actually, record Turks archery records are believed to be well beyond 800 yards, and modern attempts seem to confirm it.

Such flight shooting is only sport, obviously.

The big difference is that flight shooting uses flight arrows, which are built very differently. The highest range I've seen for a hunting or combat arrow is three hundred odd meters, which is still quite high.

[Spiryt]

The big difference is that flight shooting uses flight arrows, which are built very differently. The highest range I've seen for a hunting or combat arrow is three hundred odd meters, which is still quite high.

Which is precisely why I wrote "sport".

As far as 'differently build' flight arrows - there was obviously huge variety here as well - from 'just light' arrows trough very thin ones with 'target' points... That could be most probably still used in fight to pepper enemy lines from large distance.

To minimally fletched short sticks weighing less than some bullets, that couldn't be shot without sipers because they were too short.

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Those were obviously used to set all those fantastical range records.

[fusilier]

Heavier bolts, will have, comparatively, better flight characteristics than light ones.

I don't disagree with you there. There are certain "economies of scale" that take place, the main problem being that as the projectile gets heavier, it requires more energy to accelerate it in the first place.

[Galloglaich]

European crossbow bolts which have survived from the 15th and 16th centuries are around 80-90 grams in weight on average, though in most cases this is without the fletching. I know of one collection in Austria which had about 400 of them from throughout Germany, Austria, Hungary and Czech.

Longbow arrows were around 50-60 grams, most of the Steppe recurve arrows were around 40 grams, flight arrows were lighter.

Crossbows also had 'flight' bolts though which were lighter.

They definitely did use crossbows for arched shots.

Leo Todeschini of Tod's stuff managed 48.5 m/s shot last year with a 125 gram bolt. Not great but it's about the same as he managed with much lighter (60 gram) bolts.

As for the accuracy issue, I can't say. Most hunters I know say that modern crossbows are more accurate than bows. Every historic account I've read from the 13th-16th century summarized the crossbows as being more accurate than bows-including the Mongol and Turkish.

G

[Incanur]

Note that the bolt Payne-Gallwey shot 440ish yards weighed 3 ounces (85g). No hand-drawn bow can send an arrow of that weight so far. While the Mary Rose arrows appear to have been in the 45-65g range and another surviving arrow is around 50g, Matthew Strickland and Robert Hardy in The Great Warbow argue that heavier arrows - up to 4 oz - were common. Various extant Manchu war arrows are 100g and over, so this isn't hard for me to believe.

As far as accuracy, in addition to Humphrey Barwick's claim, I'll mention that Fourquevaux gave a specific account of a single crossbower a siege in the 1520s who killed more of the enemy than five or six of the best gunners. Unlike Barwick, Fourquevaux considered both bows and crossbow more accurate - or at least more reliable - than guns.

[Galloglaich]

This might be of some interest here: a first-hand account of a knightly duel in Germany in 1481

http://talhoffer.wordpress.com/2011/...knightly-duel/

G

[Yora]

That's real gold there.

Though given that the lord had 600 men prepare the battlefield, it must have been an impressive crowd. Which likely means it was a rather rare event.

[Brother Oni]

That's real gold there.

Though given that the lord had 600 men prepare the battlefield, it must have been an impressive crowd. Which likely means it was a rather rare event.

Given that they had been petitioning for 4 years to have this duel, you might as well make the most of it and turn it into a grand spectacle.

I figure that their lord thought 'if I'm going to potentially lose two landowning knights which would completely mess up my power base and internal political structure for some time, I might as well let people watch and bloody well enjoy it'.

[Galloglaich]

These two 'knights' were also more than mere knights, they were both obviously pretty bad-ass warlords, more than capable of causing trouble. They both showed up with over 200 supporters, (which was a number very likely agreed to in advance) so the 600 guys the lord had there may have simply been to keep the peace.

I know Rosenberg in particular was from a very powerful family.

http://en.wikipedia.org/wiki/House_of_Rosenberg

Their ancestral home castle, in the is one of the most impressive I've ever seen, in the beautiful town of Cesky Krumlov

http://en.wikipedia.org/wiki/Ro%C5%BEmberk_Castle

G

[Mr. Mask]

Could anyone tell me a bit about some very primitive fort designs? I was thinking of one which would be a construction of trees and rocks, crudely fashioned together with clay. The fort would be for a tribe about a couple of thousand strong, who aren't well organized nor skilled with the construction of defences.

[Rhynn]

Ring forts were common iron age forts. Hill forts go even further back.

You may need to definite "primitive," though. If you're talking Neolithic, there pretty much were no fortifications. (Although tribes thousands strong were probably not common either.) However, the Maoris apparently did build fortifications with prehistoric technology. (Of course, chronologically, that would be conciding with hill forts, but the technology levels were different.)

Note that the tribe wouldn't live in the fort - they'd live around it and shelter in it during raids, etc. Things would get damn cramped, especially when they're going to bring in their animals, too.

[warty goblin]

Could anyone tell me a bit about some very primitive fort designs? I was thinking of one which would be a construction of trees and rocks, crudely fashioned together with clay. The fort would be for a tribe about a couple of thousand strong, who aren't well organized nor skilled with the construction of defences.

One thing to note about historical constructions and creations: they tend to be very far from crude for the most part. This is particularly the case for largescale constructions requiring the input of much of a tribe - hill forts for instance are very well designed defensive works.

Remember, for most of history most people spent most of their time working with their tools and hands, and would have been extremely skilled at what they did. Even if a tribe doesn't have previous experience building fortifications, they probably are quite familiar with the tools and materials they're working with, so there's no reason for the standards of construction to not be excellent.

[Rhynn]

In fact, some ancient / prehistoric construction is so damned good that half the History Channel is now about how aliens had to have helped build it.

[Mr. Mask]

Rhynn: The examples given in the hill forts article are very inspiring, thank you .

It is as you say about living in forts. The conditions would become very bad with so many people and animals living closely together, unable to stretch their legs outside of the ramparts (unless they'd like an arrow somewhere between the shin and thigh). I'll have to do some research into how bad health issues would become in how much time based off how much population density, later on.

As for the aliens... yeah, a lot of people don't give enough credit to people who lived in ancient times. "OMG, they don't even have smart phones, everyone from fifty years ago was retarded!" I suppose is the line of thought.


Goblin: Reflecting on your point, I see where I erred. If it were a case of say, a tribe trying to build a Roman fort--then you'd start to see some pretty crude construction, as they weren't sure of the tools or what they were doing. So long as they work with familiar tools and concepts, I guess only a lack of manpower, time or resources would result in crude construction?

While there are problems of the latter's nature, I still thought too strongly of poor fortifications, I feel.

[Brother Oni]

While there are problems of the latter's nature, I still thought too strongly of poor fortifications, I feel.

Even if they weren't too sure of what they were doing, there's a difference between poor construction and poor design.

You could have the best quality construction but if the design is poor, then the fort is still going to get over-run.
Poor design could result from anything like a crappy architect (structural flaws and/or poor layout), to being unable/unaware to adapt to technological advances (the change from square to rounded towers with the advent of cannon for example).

An Iceni hill fort, designed to hold off infantry and chariots, is going to look particularly crude to a Roman legion, who would probably do their equivalent of 'LOL' before cracking it open with catapaults and other siege weaponry.

[warty goblin]

An Iceni hill fort, designed to hold off infantry and chariots, is going to look particularly crude to a Roman legion, who would probably do their equivalent of 'LOL' before cracking it open with catapaults and other siege weaponry.

I vaguely remember reading about a Roman assault on a hill-fort at one point. My recollection is that the work was rather speculative, but the authors concluded that the fort posed a significant obstacle, one that required a risky and difficult assault.

Hill-forts, being giant earthworks, would be pretty close to catapult proof for one thing. Catapult stones do OK at breaking wood and stone, but they don't really remove that much dirt. It would take a long time to worry a hole in an earthen rampart, and many hill-forts had multiple rings.

[Rhynn]

Hill-forts, being giant earthworks, would be pretty close to catapult proof for one thing. Catapult stones do OK at breaking wood and stone, but they don't really remove that much dirt. It would take a long time to worry a hole in an earthen rampart, and many hill-forts had multiple rings.

Yeah, actually, thinking on it, an earthen hill/ring-fort could be pretty enormous compared to stone castles, couldn't it? You don't need to move enormous amounts of stone - move this earth over here, and you've got a high earthen rampart... easier to fit in your animals and people.

[warty goblin]

It is as you say about living in forts. The conditions would become very bad with so many people and animals living closely together, unable to stretch their legs outside of the ramparts (unless they'd like an arrow somewhere between the shin and thigh). I'll have to do some research into how bad health issues would become in how much time based off how much population density, later on.

A lot of hill-forts were very large, large enough that they could (and apparently did) house permanent or semi-permanent settlements at the top.

As for the aliens... yeah, a lot of people don't give enough credit to people who lived in ancient times. "OMG, they don't even have smart phones, everyone from fifty years ago was retarded!" I suppose is the line of thought.

To be far more fair than alien theorists deserve, there's a lot of really weird stuff from early antiquity and pre-history. Stonehenge for instance is legitimately strange; as is the way that the cultures that built it turned everywhere they lived into a sort of giant extended landscaping project. Apparently making giant piles of dirt to pile on dead people, or dragging around ridiculously large rocks, was something of a pastime.

Goblin: Reflecting on your point, I see where I erred. If it were a case of say, a tribe trying to build a Roman fort--then you'd start to see some pretty crude construction, as they weren't sure of the tools or what they were doing. So long as they work with familiar tools and concepts, I guess only a lack of manpower, time or resources would result in crude construction?

The advantage of a hill-fort is that your resource is a hill, and all you need is a bunch of shovels. Sure they would take quite a while to make - digging trenches is hard work - but this is true of all fortifications. And unlike a stone or even wooden fort, there's no need to transport raw materials any significant distance.

While there are problems of the latter's nature, I still thought too strongly of poor fortifications, I feel.

Digging through the mental closet, I recall some interesting details of some British/Irish hill-forts, that were clearly put there to make them a real beast to assault. The earthwork rings for instance were often connected, particularly next to gateways, which would force any assaulting force to continue up a set path to the next gateway, instead of being able to attack multiple points at once and disperse the defenders. These connecting works often left short dead-end passages on one side of the gate, so anybody coming through the opening could be assaulted from all sides. Attackers would also have to make several sharp turns while pressing upwards, leaving their flanks exposed to enemies on the earthworks above. Caches of slingstones have apparently been found at various strategic locations in many hill-forts as well, suggesting that they were well prepared for an assault.

They may seem simple, but fighting uphill is hard work. Fighting uphill while people throw rocks and spears and arrows at you from all sides has got to be pretty unpleasant.

Yeah, actually, thinking on it, an earthen hill/ring-fort could be pretty enormous compared to stone castles, couldn't it? You don't need to move enormous amounts of stone - move this earth over here, and you've got a high earthen rampart... easier to fit in your animals and people.

Apparently some of the hill-forts in Ireland are so big people think they were used as cattle pens. Although given the cattle-raid intensive nature of warfare described in, say, the Ulster Cycle, a dual use hardly seems inappropriate. Not only does it keep your cows in, it makes it easier to kill the people trying to take your cows out.

[Brother Oni]

I vaguely remember reading about a Roman assault on a hill-fort at one point. My recollection is that the work was rather speculative, but the authors concluded that the fort posed a significant obstacle, one that required a risky and difficult assault.

Hill-forts, being giant earthworks, would be pretty close to catapult proof for one thing. Catapult stones do OK at breaking wood and stone, but they don't really remove that much dirt. It would take a long time to worry a hole in an earthen rampart, and many hill-forts had multiple rings.

As far as I'm aware, the angle of catapults is adjustable (if all else fails put them on a slope), thus making it easier to launch stuff into the fort itself. Showers of small stones (the equivalent of grapeshot), flaming oil or dead animals would soon make the inside of the fort extremely unpleasant for the defenders.

As with any siege, if you can't breach the walls, then the main assault is going to be focused on the gates. I know the celts had an alleged trick of throwing hornet nests into roman formations to break them up, but without those, I'd think a tetsudo would allow the Romans a better chance to clear out each ring of the fort, a layer at a time.

I'll admit that I exaggerated their response, but I'd think a fully supported Roman legion would have an easier time of it compared to a rival Iceni tribe. If all else fails, they could build their own fortifications around the fort, ala the Battle of Alesia, making any sally by the defenders a strange sort of counter siege.

[warty goblin]

As far as I'm aware, the angle of catapults is adjustable (if all else fails put them on a slope), thus making it easier to launch stuff into the fort itself. Showers of small stones (the equivalent of grapeshot), flaming oil or dead animals would soon make the inside of the fort extremely unpleasant for the defenders.

Is there any evidence of people actually shooting loads of pebbles from catapults? Gravel has crappy aerodymanics, being small, light and having lots of irregular shapes. I'd think the range you could get from such a load would be really quite low, low enough to put the crew well into the range of unfriendly people with bows. Particularly if one fires the gravel on a highly parabolic trajectory.

I'm aware of onagers firing ~four or five inch diameter rocks certainly, but that's a very different thing than showers of small stones. That's one fairly big stone shattering shields and rib cages like twigs.

As with any siege, if you can't breach the walls, then the main assault is going to be focused on the gates. I know the celts had an alleged trick of throwing hornet nests into roman formations to break them up, but without those, I'd think a tetsudo would allow the Romans a better chance to clear out each ring of the fort, a layer at a time.

The testudo has always struck me as a horrible formation to actually fight from. There's no space for anybody in it to fight, move, or even see all that well. If one uses the variant with the flanks covered by shields as well, any advance must be painfully slow. IIRC the general Roman deployment was about one man every five feet or so, and the testudo was really only used in very specialized circumstances, which is to say when the goal was to protect the army from missiles, and not to immediately carry the fight to the enemy.

I'll admit that I exaggerated their response, but I'd think a fully supported Roman legion would have an easier time of it compared to a rival Iceni tribe. If all else fails, they could build their own fortifications around the fort, ala the Battle of Alesia, making any sally by the defenders a strange sort of counter siege.

The Romans were clearly perfectly capable of breaking a hill-fort, since they did it. I never denied that, merely that it was a laughable obstacle rendered obsolete by siege engines.

[fusilier]

I know that "stone" mortars were used to throw a shower of stones contained in a basket set in the mouth of the mortar -- the stones wouldn't be as small as pebbles, but good sized stones. Of course, the range would be a lot less than a solid projectile, but it was used as a close range anti-infantry device, to break up a charge.

I would suspect that a defensive catapult would be able to launch something similar -- probably being used when the enemy was just on the other side of the wall.

[Brother Oni]

The testudo has always struck me as a horrible formation to actually fight from.

Having been in one (we were using kite shields rather than scutums though), I agree that it's very difficult to fight from and very slow going.

It's very good at getting you close to missile troops though, thus they can approach the initial gate in relative safety.

Looking up some more information, the Romans appeared to have employed an armoured wheeled battering ram of some sort also called a testudo:

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From what I know of later versions of such siege engines, they can be very to stop without some sort of boiling/flaming liquid, unsuitable terrain or the defenders sallying out to kill the crew.

The Romans were clearly perfectly capable of breaking a hill-fort, since they did it. I never denied that, merely that it was a laughable obstacle rendered obsolete by siege engines.

Alas without more detailed records of battles, we're limited to what we can replicate in computer games and experiments by rich crazy people eccentrics.

Speculation time - what type of siege weapon in your opinion would render hill forts obsolete?
I'm thinking trebuchets, although I'm inclined to think that the much later mortars would be required based of fusilier's comment.

According to wikipedia, it seems the societal changes prompted the demise of hill forts rather than military obsoleteness.

[warty goblin]

Having been in one (we were using kite shields rather than scutums though), I agree that it's very difficult to fight from and very slow going.

It's very good at getting you close to missile troops though, thus they can approach the initial gate in relative safety.

Your experience clearly exceeds mine on this point. All I know is that I don't do all that well when I can't move my elbows.

Looking up some more information, the Romans appeared to have employed an armoured wheeled battering ram of some sort also called a testudo:

Spoiler

Show

From what I know of later versions of such siege engines, they can be very to stop without some sort of boiling/flaming liquid, unsuitable terrain or the defenders sallying out to kill the crew.

Isn't there a medieval source that suggests lowering essentially a mattress on chains in front of the ram, to cushion the wall?

Alas without more detailed records of battles, we're limited to what we can replicate in computer games and experiments by rich crazy people eccentrics.

Totally there, but for the lack of funds. Well, that and living in East Central Nowhere.

Speculation time - what type of siege weapon in your opinion would render hill forts obsolete?
I'm thinking trebuchets, although I'm inclined to think that the much later mortars would be required based of fusilier's comment.

My gut feeling is that the hill-fort isn't the sort of problem that's best tackled by large and complicated bits of machinery. It's hard to move dirt around by slamming rocks into it. Even a really big trebuchet doesn't make that big of holes in the ground. Even to the extent it does, it really mostly just pushes dirt out around the projectile. Drop another shot in next to the first, and I suspect you don't get twice as big a hole, you just push dirt back into the first one.

Now you may be able to make life sufficiently unpleasant for the folks up top that they surrender via trebuchet bombardment. But this requires a lot of bombardment, and the hope they don't have a catapult to chuck stuff right back at you, with a significant range advantage.

I think you solve a hill-fort by having enough men to storm the thing. Unlike a traditional stone wall fortification after all, you can literally just walk up the sides. The gateway isn't the only point of access that doesn't require something cumbersome like a ladder or tower, just a point where walking in is a lot easier.

In some cases the fort might be built on a crag or other bit of terrain that really is essentially unclimbable from most approaches. In this case a siege ramp might not be a terrible notion. Such ramps had a long history of (eventually) successful use in Greece and the near East during antiquity.

[Monss Meg]

Long time lurker, first time poster here. And the thing that strikes me about the ring forts. is how simaular thay resemble the western front of WWI. So to ancerar Brother Oni, O would say eather the pick, or aircraft

[Brother Oni]

Your experience clearly exceeds mine on this point. All I know is that I don't do all that well when I can't move my elbows.

Hence why spears are so popular for such tight formations as you don't need much room to move back and forth with your back hand. With enough ranks of spears, you don't actually need any space since you're presenting so many sharp pointy bits of metal, simple co-ordinated walking into your opponents is sufficient.
In the later English Civil War, I think Oliver Cromwell referred to this as 'the terrible push of pikes' when two opposing units of pikemen met on the battlefield.

Isn't there a medieval source that suggests lowering essentially a mattress on chains in front of the ram, to cushion the wall?

I do vaguely remember something about this, but I'm a bit dubious about its effectiveness given the sheer weight of a siege engine ram (a recovered cap of a battering ram used for mining weighed 150lbs, so the wooden part must have weighed at least that to keep balance).

There's also nothing to stop the crew trying to disable the countermeasure.

Now you may be able to make life sufficiently unpleasant for the folks up top that they surrender via trebuchet bombardment. But this requires a lot of bombardment, and the hope they don't have a catapult to chuck stuff right back at you, with a significant range advantage.

True. By the time that trebuchets were in vogue, warfare was generally a lot less asymmetric than the original scenario in question (Romans versus ancient Britons), so simply chucking stuff back is a viable option.

Long time lurker, first time poster here. And the thing that strikes me about the ring forts. is how simaular thay resemble the western front of WWI. So to ancerar Brother Oni, O would say eather the pick, or aircraft

Welcome!

I think I should have worded my question a bit better - what's the earliest siege weapon that would have rendered hill forts obsolete?
These days, almost any type of fixed fortification is vulnerable to artillery or airstrikes, but you don't really need to advance that far when simple gunpowder siege weapons triggered a massive change in fortifications.

While undermining the walls of a hill fort is a possibility, I think the difficulty of doing so makes simply storming the fort a better option. As warty pointed out, the walls of most of these type of forts are piled up earth rather than stone walls, thus that's a lot of earth you need to move.