Original subtitles

Secrets Of Lost Empire - 1x06

Knights in shining armor

charging each other in great pitched battles -

that is the popular view of warfare in the Middle Ages.

In reality,

most medieval conflicts involved the attacking of castles,

and mounted knights were not much use against stone walls.

A siege against a castle could take weeks,

even months -

the attacking army

pitted against a well-defended garrison within.

By the end of the 13th century,

the science of defensive architecture had reached a peak.

Stone walls were built thicker and taller than ever before.

And archers could easily pick off advancing attackers.

To further frustrate attempts at breaching the walls,

castles were situated on rocky crags,

or surrounded by water.

But every advance in castle defense

drove attackers to devise better siege weapons.

During the Middle Ages castles kept improving.

They kept improving as weapons of attack got better.

And tactics was this eternal balance

between attack

and defense.

200 years before cannon appeared in Europe,

chroniclers make reference

to what appears to be the ultimate 13th century siege weapon -

an ingenious new form of heavy artillery

that flung huge stone balls

with such destructive power

that castle walls were reduced to rubble.

But no ancient weapon of this type has survived.

Were such claims gross exaggerations,

or did such a weapon really exist?

To answer these questions,

NOVA brings together a team of experts in medieval warfare

who believe they know the secret.

It's chaos.

It's Wednesday, I think.

I don't have a clue whether or not we'll finish.

Their task -

to build siege machines

capable of destroying a castle wall at a range of about 200 yards.

I think that the thing'll smash it up nicely, yes.

With just two weeks to meet the challenge,

a siege mentality quickly sets in.

No modern builders have ever managed to do this before.

And the whole thing could twist and kick quite alarmingly.

This interplay between defenders and siegers,

it's still up in the air.

We could still take it, then again, we could fail.

It's sort of in the lap of the gods.

Major funding for NOVA

is provided by

the Park Foundation,

dedicated to education

and quality television.

CNET.com,

helping you choose the right technology product.

This program is funded in part

by Northwestern Mutual Life,

which has been protecting families and businesses for generations.

Have you heard from the quiet company?

Northwestern Mutual Life.

Additional funding for this program is also provided by the David H. Koch Charitable Foundation.

And by the Corporation for Public Broadcasting

and by contributions to your PBS station from viewers like you.

Thank you.

In the year 1304,

Edward Longshanks,

more formally known as King Edward I of England,

mounted the greatest siege of his reign

against the Scots and their castle at Stirling.

The attack dragged on.

Impatient for victory,

Edward ordered 50 carpenters to immediately begin building a monstrous new weapon -

so powerful

it would breach the strong walls of Stirling Castle.

Details about the weapon design are tantalizingly vague,

except that it was nicknamed Warwolf,

and its appearance outside the walls

terrified the garrison.

Was it the atomic bomb of the Middle Ages?

With one blow,

Warwolf leveled a section of wall,

successfully concluding the siege of Stirling Castle.

What kind of a weapon was Warwolf?

What are we doing?

Are you ...

Do you want to go up there now?

Do you think you'd better take a pair plyers up in case that ...

Hew Kennedy is a Shropshire landowner and medieval armor expert.

10 years ago,

he became intrigued by a picture of a machine drawn by Leonardo da Vinci.

It appeared to be a device for throwing dead horses,

called a trebuchet.

Inspired by the power of a machine

that could hurl such heavy missiles,

Hew decided to try building one himself -

a quest which eventually led

to this piano-flinging contraption,

a mechanized catapult made from a laminated beam,

scrap metal,

telephone poles

and steel cable.

In essence,

a trebuchet is a giant seesaw

with a very heavy weight at one end

and a much lighter missile attached to the other.

As the heavier weight drops,

the lighter projectile is whipped by its sling towards the enemy.

Hew is convinced

that Warwolf, Edward's great wall busting siege engine,

must have been a trebuchet.

If you chuck a thing that heavy at a stone wall it'll shatter it.

Stone missiles are a lot more effective than grand pianos.

To test out Hew's confidence in the destructive capability of a medieval trebuchet,

NOVA is preparing some hard sandstone balls

weighing 250 pounds -

and a wall.

It's made of sandstone

and lime mortar.

In construction and design,

it is based on the upper section of a typical castle wall of the 13th century.

Hew wants to build a trebuchet

capable of knocking it down,

but at a range of 200 yards,

it will require precision

as well as brute force.

... from this point of view,

it's much more ...

Michael Prestwich, a medieval historian,

will ensure that Hew's next trebuchet

will be based on an authentic 13th century design.

And I suppose when its got to the top of its trajectory,

it starts coming down again. (Yeah.)

It really looks quite frightening.

Yeah.

But I'm glad I wasn't standing underneath it.

It would bust up a building all right, wouldn't it?

It's the first time I've seen a full-scale trebuchet in operation.

To see the high trajectory of it

and the way the missile

and the sheer speed with which it falls,

it is a fantastic sight.

Trebuchets began

in the Far East, in China.

But what they were there

were hand-pulled machines

worked by quite large teams of men.

Prepare to loose, loose.

In many ways, quite limited in what they could do.

The big advance came

when Arab engineers got hold of these devices

and put a big counterweight on

so that instead of teams of men pulling it,

the beam was pulled down by a great counterweight.

They were far more potent and far more effective.

These machines were ...

picked up by western engineers,

and by the middle of the 13th century,

it's very clear that

French, English engineers were capable of building

really quite large machines.

Some of the best military engineers were employed by Edward I -

a master of military tactics.

He was one of the most vicious and single-minded rulers of his time.

Soon after ascending the throne in 1274,

Edward decided to squash Welsh independence

and bring Wales under his personal rule.

He was a bully, frankly,

and I think many people would think of him as a really nasty piece of work.

He was utterly determined.

Nothing was going to get in his way.

Edward's strategy was to ring the mountain stronghold of the Welsh prince

with a chain of powerful castles.

Richard Holmes is an historian of military tactics.

He built eight new big castles, which were really state of the art.

They were immensely strong, well thought out.

And most of them could be supplied by water

so they were very difficult for the Welsh to besiege.

And Edward believed that you controlled the countryside

by castles like this.

They're like nails

holding the landscape down.

And their garrisons could issue out,

attack enemies in the area.

And until the castle was taken,

nobody could really dominate that landscape.

They were extraordinarily expensive to build,

and were a very severe drain on the royal exchequer.

In the short term, though,

they worked.

Edward and other English lords

designed their Welsh strongholds

with the trebuchet in mind.

For example,

Caerphilly Castle was surrounded by manmade lakes

which kept a besieging army and their siege weapons at a distance.

Castles were what modern tactitioners would call force multipliers.

They enabled a relatively small garrison

to operate at the absolute maximum of effectiveness.

And a castle like this is carefully

organized to maximize defensive firepower.

There are loopholes in the walls and the towers for archers to shoot through.

And here the walls are cunningly organized

so that the second set of walls

is higher than the first.

And therefore an attacker facing this face of the castle

not only gets the defensive fire of the first wall,

but he's got archers shooting at him

from the higher walls behind it.

It's a real nightmare.

At the end of the 13th century,

what was the effective range of an archer?

And what was the effective range of a trebuchet?

The historical reports differ.

Hew, how close are you going to have to bring your trebuchet to the walls

to do serious damage, do you think?

Probably 200 yards,

we will need to be within that to smash it up.

At 200 yards,

is Hew's trebuchet out of range of archers defending the castle?

To find out,

a dummy representing the trebuchet's chief operator is placed at that distance.

I'm sure an arrow would land amongst us if we're at that range.

You could easily shoot 200 yards with that massive bow of yours, couldn't you?

Yeah,

300 yards.

Yes.

Well at 200 yards,

I think it would be ...

putting you a bit worried, wouldn't it?

Yes, it would.

I'm the first to accept that from this sort of range

the trebuchet would be doing serious damage to the castle walls.

But I think this does suggest that ...

it's no easy business.

And the garrison that knows its business

can probably

keep a trebuchet at the very limit of its range.

And the fact that we had some going over the top

I think is mighty hopeful from the archer's point of view.

I wonder what happens if you ...

slap one into him from here?

Could I... Come on then.

It's all right, he's swallowed it, hasn't he?

Gone ... gone right through ...

right through the dummy,

kept only in by the fletchings.

Bit of a bellyacher I reckon, yeah.

Edward's castle-building campaign in Wales

had taught him how to design well defended fortresses.

Turning his attention to conquering Scotland,

did Edward also have the ability to successfully attack them?

As the king marched northwards to take the castles that guarded Scotland,

he brought with him some of the biggest siege engines,

or trebuchets, ever built.

The siege of Caerlaverock,

conducted by Edward I in 1300,

we've got remarkably a really good account of this in a contemporary poem.

It describes the way in which the knights rode up to the castle

all in their great armor,

trying to perform great deeds of valor.

In fact, they were driven back by the garrison,

hurling stones and such at them.

And it wasn't the knights,

it wasn't these people with the great acts of bravery.

It was the engineers,

men of really quite low social status in comparison,

with the great siege engines.

It was they

who compelled the garrisons to surrender.

And the poem describes the way

in which the great boulders came down from the sky, into the courtyard,

crashing down,

causing all sorts of damage and mayhem inside.

The minute the casualties started,

the garrison simply surrendered.

So it wasn't the knights,

it wasn't a great act of chivalry to capture this castle.

It was the work of the experts, the engineers.

It's difficult to tell, I mean ...

that one's obviously got a ...

Joining Hew Kennedy in his quest to build a trebuchet

is mechanical engineer Wayne Neel,

a professor from Virginia Military Institute.

... is the golden section.

This one actually is one to two, and this is one to three.

Wayne will design the trebuchet.

He is basing it on a picture he found in a 13th century Spanish manuscript.

The illustration gives no idea of the true scale of the trebuchet

because the artist has made the machine smaller

than the soldiers standing next to it.

If the drawing isn't practical from all points of view,

you begin to wonder about all the other points of view.

It may be that the things they have got in the right proportion they did by accident.

Even an artist like Leonardo will draw a plan for something that is totally impractical,

but it indicates how it could be made.

That's all.

It indicates how it could be made.

With the manuscript as a starting point,

Wayne uses a combination of engineering theory

and trial and error

to come up with a working model.

The prototype looks promising to Marcus Brandt,

a carpenter who will help Wayne build the trebuchet.

But there's a problem.

The model rocks dangerously.

This would be a serious flaw

in a full-size trebuchet with several tons in motion.

The machine basically tends to wanna ...

tip forward as that weight comes down.

It wants to drop straight down,

so it tends to pull the machine forward making it in this case tip.

To resolve the problem,

Wayne re-examines the medieval illustrations of this type of trebuchet.

He's struck by the fact

that many have wheels,

so he decides to build a new model.

Not only do wheels eliminate the tendency for it to tip over,

the movement also boosts the trebuchet's performance.

Shoot away, come on.

Hew doubts that wheels will make a trebuchet throw farther,

so he insists on a demonstration.

For the first throw,

Hew holds down the model.

The projectile travels 20 feet.

Now let's try it with - letting it loose.

Yeah. Well, it's certainly better, isn't it?

Yes. I didn't ...

When the trebuchet is allowed to roll,

the missile goes an extra 10 feet.

Why?

The falling counterweight drives the trebuchet forward.

Like a pitcher stepping forward,

this adds momentum to the throw.

The forward motion also permits the counterweight

to drop further in a straighter line.

The closer the counterweight follows this optimal path,

the more energy it captures for throwing.

What I find odd is the idea about it moving and having to move

in order to give more energy to the missile.

I would have thought this was -

on the face of it, nonsense.

But obviously if Wayne's tried it,

and it goes further, then it can't be argued with.

Now that Wayne has confidence in his model,

the project moves to Loch Ness in the Scottish Highlands

for a full-scale test.

The trials will take place in the shadow of Castle Urquhart,

which may have been besieged with similar weapons

during Edward I's Scottish campaigns 700 years ago.

Wayne and Hew arrive at Castle Urquhart

to inspect the timber that is delivered by barge.

As in the Middle Ages,

heavy duty English oak

is the choice for building the carriage and trestles.

But the throwing arm will be made from a more lightweight wood,

Douglas fir.

Wayne calculates

that a tree trunk of at least two feet in diameter is needed

to withstand the stresses of hurling 250 pound balls.

How about this one, Wayne?

It's the right size.

That would be the right diameter.

Be a shame to cut that down, wouldn't it?

Yes.

Let's get the chain saw and whack it down.

Would we have a go?

Get out of it!

Haul away.

After it is floated across Loch Ness,

the log is quickly hauled ashore.

Work immediately begins

on hewing it into an eight-sided throwing arm.

The next job is to assemble the base.

40 carpenters,

mainly from the United States,

but also from Britain and Germany,

have volunteered to spend their vacation here.

They're all timber framers

who specialize in traditional construction techniques.

Without nails,

they connect large pieces of wood

using mortise and tenon joints.

Beautiful.

1, 2, 3 ...

While the timber framers immerse themselves in medieval methods,

Wayne employs the tools of a modern engineer

to check and recheck his design.

In particular,

he's hoping that the wheels will give him the same boost in performance

as they did on the model.

Spin on, spin on.

Up at the target wall,

work is almost complete.

The wooden structures on top

are called hoardings.

They provided additional protection for defenders

during the siege.

Attackers would build similar barriers

to protect the trebuchet team

from arrow fire.

Well, this is the target wall

that we've got for the trebuchets -

a modern reproduction of a castle wall.

It's a pretty good reproduction I think,

it's got all the details of the crenelations.

And what's important about it

is the width.

It's a good five foot thick.

The way that it's formed

is that there's an outer skin on either side,

and within that a fill of rubble and mortar.

And that provides a very solid core.

This is exactly how they did it in the Middle Ages.

And ...

I'm very glad that I'm not standing here

while the trebuchets are actually shooting.

The target wall is modeled on the outer walls of Harlech and Caerphilly,

two of the best defended castles in Wales.

Faced with the daunting task of taking a castle like Caerphilly,

what siege tactics would an attacker adopt?

A castle like Caerphilly,

like this one,

presented an attacker with a knotty problem

because it's got layers of defenses,

with sandwiches of water between them.

A bit like the layers of an onion.

So an attacker arriving here

would encounter the moat,

a water defense,

so that he couldn't mine underneath it without his trenches being flooded.

His best bet if he possibly can

is to take the place by surprise or by guile.

To trick his way in -

to get in before the garrison's ready for him.

If he can't do that,

he's then got to mount a formal siege.

And ultimately ...

he'll starve it out.

Gates had once been the castle's weakest point.

But by this stage in history,

they'd become its strongest.

They're defended by gatehouses,

these are very powerful towers

with arrow slits in them.

So anyone attacking the gate is subjected to close-range fire.

And there's a portcullis

which drops down just behind the attackers,

and even if an attacker does manage to take the gatehouse,

then he's got another moat,

two more gatehouses,

and he's got to do the whole rotten business

all over again.

Meanwhile, rotten weather has besieged Castle Urquhart.

And after a week of daily downpours,

the trestles that support the throwing arm

are ready to be raised.

Pull.

Pull.

Pull.

At the top of the trestle,

the throwing arm rotates on an axle

that has to be both strong

and exact.

... and counterweights so it has to be fairly precise ...

Marcus Brandt has taken on the job.

Well, we've got to address the issues of axles.

We've got two sets of axles with this fixed arm,

fixed counterweight machine.

We've got the axles down here to carry the wheels,

and we've got this more precise axle up here

which carries this 8 tons of weight and ...

arm.

And it has to be fairly precise.

We've set up a great wheel lathe

which is a precursor to modern lathes.

It's just a great big flywheel.

It's powered by muscle

and it turns this 10" x 10"

down to an 8" x 8".

Marcus restores old buildings in Pennsylvania,

and has enthusiastically embraced the idea of using medieval technology.

It's a very medieval feel to the whole project.

We've got all the trades going at once.

We have the stone masons busy,

we've got all the carpenters and the axes flying

and the chips and the smoke and the mud.

Boy, if ...

if it weren't for the jets flying overhead occasionally,

you'd think you're in the 12th century.

Villages were often established

next to the castle of a nobleman or the king.

English society was very hierarchical,

with the king and his nobles at the top,

and then the rest of society cascading down from that.

Now the castle wasn't just important militarily,

they were an economic power as well.

There were communities built up round the castle

to supply it.

And the castle provided protection as well.

At their best

these noblemen were protectors,

at their worst they were ...

often something rather like mafiosi, uhm...

leeching off the local countryside.

So living under the shadow of a place like this

had advantages,

but disadvantages too.

How you doin', Phil?

Goin' up too much there?

In order to position the heavy throwing arm,

the timberframers place an A-frame

above the trestles to support the pulley system -

a standard medieval device.

A block and tackle

dramatically reduces the number of people required to pull on the ropes.

Now block and tackle is a fairly simple device.

It magnifies your pull.

If I were to lift my own body weight with a single rope,

I would have to pull down 200 pounds

to lift my 200 pounds of body weight up.

With this,

I'm hooked up to this double sheath pulley,

and I've got four lines which share the load equally,

so 200 pounds here

is only 50 pounds on each one of these ropes.

So to lift my 200 pounds up,

I only have to pull 50 pounds here.

Now mind you, I have to pull four times as much rope,

but it really works.

The next phase of construction

is the most dangerous.

Without the help of a modern crane,

the timber framers must trust the strength of two slender poles

and the rigging of their ropes

in order to raise the one ton throwing arm.

One accident,

one slip,

one failure hidden in the heart of this timber

and we're out of business -

simple as that.

It's looking real good right now,

going right on in there like we planned it seems.

We are in place. Yeah!

With the throwing arm in position,

Wayne needs to attach weights that will power the machine.

He chooses lead

because he believes lead was used for the counterweight of Warwolf,

the mysterious and terrifying siege engine

that clinched the assault on Stirling Castle.

There is good historical evidence for this.

In a letter Edward wrote just before the siege,

he demanded that lead be removed from all the churches.

One of the things that they needed for the siege of Stirling

was heavy weights for the counterweights on the engines.

And they sent orders out

to strip all of the church roofs in the entire surrounding area.

So all of this lead, lead sheets, would have been brought to the siege

and then melted down in order to form the counterweights.

Wayne's calculations tell him

that in order for his machine to throw a 250 pound ball,

he'll need about six and a half tons of lead counterweight.

It takes a week to melt down the scrap

and form it into a collar that can be bolted onto the arm.

Wayne's come up with a really neat solution

for a lead counterweight made various pieces

bolted together.

But it is expensive.

Lead is difficult to get hold of.

It's complex to make this.

There is a much easier solution,

which is to use a large box as a counterweight.

Something like this,

which you could fill with earth, with stones, with anything you'd got.

Fill it up.

You could put as much or as little in as you wanted,

and that would affect the range of the machine.

And you'd simply then have to put this ...

box on the machine,

swiveling ...

roughly like that.

A survey of medieval illustrations suggests

that swinging counterweights were the more popular design.

A man who has been working with them longer than anyone else

is traditional French carpenter Renaud Beffeyte.

Renaud is convinced that Edward's great siege engine, Warwolf,

had a swinging counterweight box.

The simple design of the box makes it not only cheaper,

but easier to build than one with a lead counterweight.

Here we got.

And Renaud has found graphic accounts

of the destructive power of some really big siege machines.

I found account medieval -

An account, -Yes.

a medieval account.

And they pay 300 bullets in three days,

then they shoot 300 bullets on the same place on the same wall.

After three days, the wall was destroyed.

So you think the real purpose of something like this

is ...

is simply to ...

attack a castle from a distance

and bring the wall down?

Yes. Yeah, yeah.

500 years before Newton's apple,

medieval engineers had figured that trebuchets with a swinging counterweight

are the most efficient at using the force of gravity.

Like adding wheels to a fixed-counterweight trebuchet,

the hinge allows the swinging counterweight

to descend further in a straighter line,

capturing more energy for the throw.

15 years ago,

Renaud came across the notebook of the 13th century French architect,

Villard de Honnecourt.

In it he found the plan for the base of a trebuchet

and a description of the swinging counterweight box.

Unfortunately,

the page showing the rest of the trebuchet was missing.

But with his knowledge of medieval carpentry

and his experience of building over 30 small trebuchets,

Renaud realized that if the design were ever built,

it would be monstrous -

the height of a five-story building.

Ever since this discovery,

Renaud has wanted to construct the full-size trebuchet.

Finally, he will get the chance at Castle Urquhart in Scotland.

At the start of a medieval siege,

a trebuchet engineer would typically seek out

as big a throwing arm as possible.

Renaud inspects a good-sized oak log that he hopes will be suitable.

Using the same geometric principles

employed by the medieval engineers who built castles, cathedrals and siege machines,

Renaud starts designing his trebuchet.

The key decision is where on the throwing arm

to position the main pivot point, or fulcrum.

Medieval engineers worked this out by observation.

In this largely illiterate society,

carpenters used animal figures like these

as an aid to remember geometric formulas.

Now that Renaud knows where to put the main axle,

he can design the trestle,

base

and capstans

to raise the counterweight box -

because they are all sized in proportion to the throwing arm.

But just as he begins building the trebuchet,

Renaud is called back to France.

In his absence, work progresses on the base.

Work also begins

on drilling out the main axle hole in the throwing arm.

Unfortunately,

there is some confusion about the size of the opening,

and a nasty surprise awaits Renaud's return.

Hi.

Good morning. Hi. Good morning.

Renaud's been away for a couple of days,

and while he was away, we cut the axle hole.

It's quite apparent that a lot of meat has gone from the timber

and we're left with quite thin sections on either side.

I think the beam,

the throwing arm, can break here,

in this part.

Renaud's concern is that we've gone

too much to this extreme where we've taken out too much wood of the throwing arm

and made the axle too strong,

and his concern of course is that on our first throw,

that it's going to do something like that.

Renaud is left with no alternative

but to hope that a couple of planks will be strong enough

to splint the weakened throwing arm.

Finally,

work starts on raising the great trestles.

With each passing day,

the situation at Castle Urquhart more and more resembles a siege of old.

With two trebuchets to finish,

there is a nagging feeling that Renaud's machine may not get done

before the timberframers must return home.

Over at Wayne's trebuchet,

work on attaching the lead weights is finally finished.

All that remains

is to cock the arm.

Even with the help of pulleys,

this requires 40 people.

With a 13,000 pound counterweight,

it's a much bigger job than any one imagined.

And it will have to be repeated for each fling.

The trigger mechanism is not strong enough,

and buckles alarmingly

as it takes the full weight of the throwing arm.

It's bending as we're releasing the arm,

and we're wondering whether it can hold the weight right now.

To avoid an accidental firing,

they reinforce it with a length of chain.

They've got lots of engineers on this and maybe they've got it right,

but I think it's quite difficult to get it right.

It's chaos,

the sun is going down,

I don't have a clue whether or not we'll finish

even one of these machines on time.

Well, we're under the gun now.

It's kind of touch and go whether we're gonna get this thing put together

and actually fling both machines,

but if I know this crew,

come hell or high water, we're gonna make this thing fling.

There goes your light (laughter).

The next morning a 250 pound sandstone ball

is quickly positioned in the sling for the first throw.

I'd rather have a blow this long...

It's got about a 50 percent chance of going in the right direction.

It could go in the lake there by mistake ...

because these adjustments are ...

not well known to us.

You ready?

This is it.

One,

two,

three,

fire in the hole!

Even with 12 timber framers pulling,

the firing pin won't budge.

It's quite normal that, I mean, triggers are very stiff.

We found that at home.

It takes a lot of effort,

which is as well, in some ways.

Despite Hew's predictions that a trebuchet on wheels would shake itself to pieces,

the reverse is true.

Wheels dampen the recoil.

Everything appears to be working as Wayne predicted,

except the range.

The ball only traveled about 170 yards,

falling short of the wall.

What are we ...

30 yards short, and about 5 feet low.

I thought the throw was flat, which means we've got to -

I think shorten the sling so it releases sooner

and goes higher, which should get us to the wall.

Just like his medieval counterpart,

Wayne uses a process of trial and error

to alter the trebuchet's range

by adjusting the length of the sling.

With the first throw,

a long sling resulted in a late release

and a low trajectory.

By shortening the sling,

Wayne believes the ball will be released earlier,

resulting in a higher path.

Wayne's adjustments have the desired effect.

The second throw has perfect range,

just missing the target to the right by two feet.

I think we took the King's ear off.

Good job, Wayne!

So it needs a slight adjustment,

and then it would be a direct hit.

Tomorrow is another day.

What will be the last day for Wayne and his team dawns,

with the wall still intact,

but clearly under threat.

Meanwhile Renaud's trebuchet is still not finished.

This morning they rush to complete the counterweight box

that is hinged to the throwing arm.

We've got the one treb built;

the other one is about 99% of the way there.

We flung two stones last night with Wayne's treb,

but we really don't want to let Renaud down,

and we don't want to let ourselves down.

We really want to see this thing fly before we go.

Still,

with time so short,

it's unclear that Renaud will get a chance

to fire his trebuchet at all.

After last night's narrow miss,

Wayne's trebuchet is repositioned to be more in line with the target.

All we're doing is shifting it slightly to the left.

We were throwing to the right a little far.

So we've shifted it about one inch,

so that hopefully we'll be dead on center.

With the same 250 pound ball as yesterday,

and the sling at the same length,

Wayne believes he is now dead on

to hit the wall with his third attempt. (... three, two ...)

... one.

Fire in the hole!

The third shot is identical to the second in distance.

At a range of 200 yards,

adjusting the wheels one inch to the left

placed the missile bang on top of the hoarding.

We've gotten wood,

I don't know if we've contacted any stone yet.

But we've knocked the hoarding pretty well.

It was maybe a little high,

and we've come down a little bit.

That must be the old hole there, mustn't it?

That's the hole.

It's still a bit on this side, isn't it?

If you'd been standing under that hoarding, you'd have had a jolt.

With the trebuchet lined up on the target,

Wayne only has to shorten the range by a hair

to hit the stone battlements below.

So this time what we've done is lengthen the sling about six inches,

so we're hoping to fire a little bit flatter

and get to the top of the hole -

the top of the wall.

It's quite difficult,

I think probably, isn't it, on those small adjustments?

I mean, do you think -

Yes, small adjustments are difficult to do.

We could ...

perhaps not get so lucky this time,

but it's been very good so far, hasn't it? (Well, we'll see.)

Worried that this may be the last attempt,

Wayne makes a sudden change of plan.

He replaces the 250 pound ball that he's been using

with a jumbo 300 pounder.

Wayne figures that the heavier ball,

clocked at a speed of 127 miles an hour,

should breach the wall.

But he is wrong.

We're going back to the 250 pound ball, instead of the 300

and see if we can get a little bit more height.

They've only got time for one more shot,

the American team, and ...

they've been very near,

but they might miss it again.

And if they don't get it,

do you think you can get it with yours?

Maybe if we are more lucky, then we can destroy this wall.

Yeah.

Well, we'll see.

It's French against Americans.

No, it's - no, no,

it's not against.

That's your way.

Putting on their kilts for good luck,

Wayne's team rushes to get in one final shot.

We did it!

Come and take a look at the rocks over here.

It just pulverized the stone on the inside.

It confirms what we came here to prove, didn't it?

We - they've had a lovely hit, smack in the middle,

and it smashed it.

And it's busted it right through to the back.

So it's quite obvious that if you've got one of these trebuchets

and you've got a castle like this,

and you've got plenty of time to shoot it,

you're going to knock it into a powder.

We can reduce this to rubble.

Intoxicated with success, the timberframers bid adieu to the Highlands.

But the next morning,

Renaud is heartened to find that he's not been completely abandoned.

Ed Levin

and a handful of the Americans have decided to stay on in Scotland

to help finish the job.

I'm sure it's good enough.

No, it's linking to the second... What's happened?

The biggest concern

is whether the throwing arm has been fatally weakened

at the point where the main axle passes through it.

To avoid stressing the arm,

Renaud decides to only partially load his counterweight,

using four tons of sand in the 12 ton capacity box.

But there are risks to this approach.

We're all suitably cautious

in having the 250 pound sandstone ball end up in the castle wall rather than in the loch,

or drop down on the machine, or ...

any of the other places it has historically been known to go.

Nobody knows quite what they're doing,

so that's what makes it fun.

A moment of birth.

And terror.

Yeah.

Well, birth is usually accompanied by terror.

Now we are ready for shoot.

It's ...

getting me nervous.

... three,

two,

one,

fire in the hole!

The heavy ball and relatively light counterweight

result in the missile landing dangerously close to the trebuchet.

Well yeah, I mean,

we knew that there wasn't enough weight in really, didn't we?

It was just an experiment.

The counterweight is not so heavy.

We must put two bag more.

Two tons.

Of sand.

Yes, of sand, yes.

Two more tons of sand are added.

I don't think there's enough weight for it to go really well yet.

This machine wants a lot of weight.

10, 12 tons probably, to make it go properly.

Renaud thinks if we keep putting little bits in,

he might just get there without busting the axle,

which is natural, of course, because it's his machine.

Fair enough.

Five!

We are going to get a good shot. (Four!)

I'm sure, sure, sure. (Three, two ...)

... one,

fire in the hole!

Renaud's optimism is justified.

The missile falls just a few yards short of the wall

and a bit to the right.

The team decides to give it one more day.

But the next morning starts with snow,

followed by a heavy downpour.

Well, basically we're at the last day, we've got -

between the rain and the mud, we've got a rigger's nightmare.

It's really taken its toll on the ropes,

the mud grinds in and it starts tearing up the fibers.

The water helps make the rope stretch,

and if you look around the place,

there's ropes in the mud and no rigger likes seeing that.

So we're doing the best we can to keep our ropes clean,

but it's an uphill battle.

Last night's final shot was short of the wall

because it was thrown too high.

Renaud believes

the sling is slipping off its prong too soon.

So to delay release and lower the trajectory,

the prong is bent forward.

We've got the right amount of loft,

we've got the right amount of range,

we're just ...

missing the target off to the side.

For days, Renaud has suspected

that his trebuchet is pointing just to the right of the wall.

But the loaded machine is too heavy to shift,

and he faces the possibility

that he may have to go home

having achieved only a near miss.

At the last minute,

Marcus offers a solution.

If we had our preferences,

we'd be able to move the machine over a little bit,

but we're afraid of shattering the machine,

particularly with all the weight in the basket.

So we're gonna move the channel of the ball

a little bit to the side so we can change our angle of attack.

The range is good,

but we just want shift it over to the left a bit.

By shifting the channel that holds the ball slightly to the left,

they hope to redirect the missile.

It works -

almost.

Another three feet and Renaud would've had a direct hit.

Unless shifting the channel was just a fluke,

one more nudge to the left

should bring the trebuchet right on target.

Go, baby! Come on!

Oh, that looks good!

Perfect, yes. At right.

Yeah!

After two throws which are slightly high of the wall itself,

Renaud orders a minute adjustment of the prong

in order to lower the trajectory.

With frayed ropes and a storm threatening to close down the siege,

everything now hangs on Renaud's ability to quickly get on target -

and he does.

A bull's eye on the battlements.

Well done!

This whole wall, if you run your eye down here,

it's bellied out,

there's cracks all through it.

Anybody standing back here would've been mincemeat.

In a real siege

it would only be a matter of time

before the wall is reduced to smithereens.

In terms of the kind of dialogue that existed between attack and defense,

it is very clear now to me that the ...

appearance of the trebuchet on the scene shifted that balance radically in favor of attack.

I've gained tremendous respect for the medieval engineers.

They were able to build a ...

frightfully powerful

and highly accurate and easily adjustable machine.

If you're under siege,

you've got to try to knock these things out before they're actually built,

cause once they're built, you're sunk.

The trebuchet is ...

this big machine who can broke the wall

and also ...

a trebuchet must be the ...

Wolfwar.

Warwolf.

Wolfwar?

Warwolf.

Warwolf.

It's so difficult,

we must change this name.

Warwolf.

It is clear from the experiment

that both types of trebuchets work.

Because it could so easily be increased in weight,

the swinging box design was the improvement

that tipped the balance in favor of attack.

So the great wall-busting siege engine Edward employed at Stirling Castle

was almost certainly a trebuchet

with a giant swinging counterweight.

The weapon that dominated siege warfare for 200 years.

It was not until the late 15th century,

the end of the Middle Ages,

that the superiority of cannon clearly emerged,

and the trebuchet ...

vanished into the mists of time.

Become a medieval engineer.

On NOVA's Website,

build your own trebuchet

and knock down the castle walls.

Converted into subtitles by m06166