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Weapons that Changed Warfare: The Trebuchet

Once upon a time, if you lived in a castle, you were pretty safe. There might be a war waging all round you, with men being impaled on lances, run through with swords, stabbed with daggers or cleaved – or is that ‘cloven’ or maybe ‘cleft’- with battle axes, but you were well out of the action.

For a start, your fortress would have been built on the top of a hill and, if there hadn’t been a hill in the right place at the right time, the builder would have ordered one to be constructed. Below the walls would be steep ramparts of rough boulders, practically impossible to scramble up carrying any sort of weapon. Beyond that would be a moat. Depending on your locality and the local climate, that could be anything from a diversion of a flowing river to a stinking ditch of stagnant water – a particularly good defence in times when swimming was not considered a necessary accomplishment that all children should acquire.

Entrance to your stronghold could be gained only via a single bridge and – just to make life more fun – it was sometimes a drawbridge, so you could cut off you enemy’s access in advance or leave raising it to the last moment and chuck them all into your stinking moat. Mind you, to have got that far, they would have had to have breached your outer walls, which would have been defended by archers on the ramparts and sundry other lackeys pouring boiling oil on the enemy’s heads.

Of course, the gates were a kind of weak point, but they were iron-studded and made of the stoutest timber available and the gate towers were just designed for the pouring of boiling oil. And a hundred strong men, manhandling a giant tree trunk to bash down your gate, made the perfect target.

On the whole, everything was in your favour.

Even when the enemy got clever and devised a system whereby the battering ram was suspended from beams so that it could be swung at the gate or the wall with greater force; even when they capped the business end with iron; even when they built a roof over it to protect the those manning it from the boiling oil; even when they covered the roof with wet hides so that your buckets of burning tar could not set light to it; even when they mounted it on wheels – you still had the advantage.

In most cases, your enemy had only one real chance and that was to camp outside your gate and try to starve you out. The success or failure of this strategy depended not only on the castle’s supplies of food and water inside the walls, but also on the loyalty of the besieging troops when faced with adverse weather. Many a siege failed because soldiers – particularly if they were mercenaries – deserted at the onset of winter.

Safely in your castle – albeit on short rations – all you had to do was to sit out the siege and pray for snow. On the whole, everything was still in your favour.

Then things started to get mechanised

Battering rams had proven reasonably effective because the wall-building materials of the day, such as stone and brick, were prone to cracking when impacted with force. With repeated blows, the cracks would grow steadily until a hole was created. The main drawback of the ram was that it involved getting up close and personal. No matter how cheap human life was considered to be in those days, there was a limit to the amount of manpower a commander could expend on suicide missions. They needed to be able to chuck stuff from further away.

Picture by havos123 from Pixabay

Derived from the crossbow, the ballista took advantage of advances in torsion spring technology. Fibres twisted together under pressure stored potential energy which, when released, could operate a mechanism to propel a heavy missile a considerable distance. The Greeks developed several weapons based on this principle but it was only under Philip of Macedon and his son, Alexander the Great, that the ballista became the siege engine of choice, doubling as field artillery.

The ballista could be a highly accurate weapon over a short range, knocking down individual soldiers, by all accounts. But it wasn’t so accurate over longer distances. Nevertheless, the Romans carried on developing the ballista and Julius Caesar used it during his conquest of Gaul and on both of his campaigns in Britain. The round towers around the walls of London were erected to provide platforms for permanently mounted ballista defences.

Another torsion spring device used by the Romans was the onager, which fired both rocks and arrow-shaped missiles. Unlike the ballista, which had twin arms, the onager had a single arm. It was very awkward to move around, difficult to aim and needed eight men to wind down the arm. It was pretty useless as a defence weapon because its recoil would demolish the fortifications on which it was mounted.

It was time for something new.

Enter the trebuchet

Trebuchet  by Lars K Jensen is licensed under CC-BY

There seems to be no mention of the seesaw as a piece of playground equipment before the 17th century but such a simple contraption must surely have been in existence long before that. Archimedes once said: Give me a lever long enough on a fulcrum and I’ll move the world. Surely someone of his time must have worked out that putting a beam on a fulcrum would enable two children to move each other? Be that as it may, let’s use the seesaw to explain what was to become the deadliest piece of war machinery of its day.

If you apply downward force to one end of a seesaw, the other end will rise in the air. If you move the fulcrum away from the centre and apply force to the shorter end of the beam, the other end will rise higher in the air. If you then lengthen the beam and put the whole thing on a platform, you will get to a point where you can swing the other end through 180 degrees. Add a sling and a missile and you have, in effect, the throwing arm of a trebuchet.

By the time the trebuchet entered the annuls of European and Middle Eastern warfare it was already centuries old. It had made its debut in China, probably around the fourth century BC. The original Chinese trebuchet was of the type known as a traction trebuchet, or mangonel, which was powered by human effort. Up to 100 men might be needed to pull down the short end of the beam with enough force to launch the projectile from the sling fast enough to send it flying several hundred metres. It was not only large boulders that were used as missiles. Records tell of hollowed-out logs filled with burning charcoal being hurled at enemy troops. Trebuchets mounted on wheels were said to have needed 200 men to pull each of them.

The Chinese used trebuchets for well over a thousand years and carried on using them even after they had the option of gunpowder.

For example: From 1125 onwards, after a protracted war, the Jin controlled northern China and the Song controlled the south. In 1150, Wanyan Liang became emperor in the north and planned to unite northern and southern China. In 1161 his Jin army set out, planning to cross the Yangze river at Caishi, entering Song territory just south of modern-day Nanjing. Wanyan Liang’s 600,000 Jin soldiers clashed with the 18,000-strong Song forces in a naval battle. The paddle-wheel warships of the Song were equipped with trebuchets that launched incendiary bombs made of gunpowder and lime, which inflicted a decisive defeat on the Jin, despite their superior numbers.

The interesting point of this snippet of history is that gunpowder was not used as a propellant but in the missile itself. The trebuchet was still the artillery weapon of choice.

The trebuchet moves westwards

Traction trebuchets were adopted by the Byzantines in the late sixth century AD. By the seventh century, they had become a common weapon, used in both attack and defence, on both sides of any war that happened to be going on. After the counterweight trebuchet was introduced in 1272, the two types worked alongside each other and, although gunpowder was already in use in China, its slow introduction into the west meant that these weapons could terrorise the rest of the world for another century or two.

While traction trebuchets used raw manpower to provide the force to lift the arm, counterweight trebuchets harnessed the force of gravity. Instead of having a hundred men pulling on the short arm of the beam, a dozen or so would fill a large container at the short end with stones, sand or lead and winch it up,  ready to be released on command. The counterweight model could be made much larger, throw much further and required significantly fewer men to operate than traction trebuchets. But they needed a lot longer to reload. In a siege situation, reloading time wasn’t necessarily crucial but a successful army needed some of each if it was to gain the upper hand in most situations.

The first use of the traction trebuchet in the west would seem to have been in an attack on Thessalonika in AD 586. According to the Archbishop, the bombardment lasted for hours, but most of the shots missed their target. When one stone did reach the target, it “demolished the top of the rampart down to the walkway.”

The use of traction trebuchets spread through western and northern Europe. During the siege of Paris in AD 885-886, the Viking forces that had arrived from the north, stormed the city with various siege engines, including traction stone-throwing machines, 15 which they had built with the assistance of Byzantine engineers.

The Byzantine emperor, Alexios I, had trebuchets constructed to help the Crusaders in their attempt to recapture Nicaea and the rest of Anatolia from the Saljuk Turks in 1097. Contemporary reports suggest that this new design was his own and that the machines provided to the Latin Crusaders were, in fact, the first counterweight trebuchets.

However, trebuchets of either type were noticeably missing from the Crusaders’ artillery at the siege of Jerusalem two years later and it was the defenders that utilised traction trebuchets mounted on the city walls.

By the end of the 12th century, counterweight trebuchets were already employed during most large-scale sieges, alongside the smaller engines. The counterweight trebuchets were capable of hurling projectiles larger than 100 kilograms to distances over 200 metres and so inflicted serious damage on the defences.

Although the Crusaders were ostensibly involved in a Holy War against the infidel Muslims, some had a much broader definition of the word ‘infidel’ and vented their spleen on Jews and any Christian group they considered heretics. This accounts for Simon de Montfort’s attack on the city of Toulouse. (This Simon was the fifth Earl of Leicester, not to be confused with his son, Simon de Montfort, the sixth earl who, briefly, instituted constitutional monarchy in England.) In 1217, he captured the city, then lost it again and the siege dragged on through the winter.

In the spring of 1218, a certain Bertran of Toulouse suggested to the people that they construct a trebuchet for the defence of the city. The city’s carpenters got stuck in. Meanwhile, the Crusaders constructed a ‘cat’ (a leather-covered, mobile shelter) in order to approach the walls. The defenders’ trebuchet, seemingly operated by women and children, swiftly dispatched the cat. During the Crusaders’ counter-assault, Simon was hit on the head by a stone, probably from the trebuchet. It killed him.

Battle of the ‘big guns’

By the time the Mamluks launched their campaign in 1291 to recapture the city, Acre had been in Christian hands for a century. By then the trebuchet had been adapted to throw anything the warring factions fancied – and flaming bolts were a popular choice.

Baybars al-Mans described stones “resembling stunning thunderbolts” and “bearing the likeness of gleaming flashes of lightning”. Another contemporary chronicler describes stone-shot perforated with holes to contain naphtha. There can be little doubt that what are being described are incendiary missiles hurled by bolt-projecting trebuchets,

Acre had had seven months to prepare for the Mamluk siege and had reportedly made a good job of it. There would have been protective screens to cushion the blows from the boulders launched by the Mamluks’ trebuchets, but the rain of fire that preceded the bombardment would have reduced those to ashes. The trebuchets could then be refitted with slings and put into action as stone-projectors.

In all, a total of 72 trebuchets were deployed against Acre: “The greatest concentration of artillery ever assembled against any locality.” At least four of these would seem to have been large counterweight machines.

The small calibre traction trebuchets, deployed in batteries, would have produced a concentrated hail of missiles, pinning down the defenders on the battlements, so that heavy artillery could engage in its work of destruction and siege engines were advanced against fortified positions. Given the slow firing rate of the counterweight trebuchet, its effective use in siege operations depended on sustained volleys from a large number of traction trebuchets to send defenders diving for cover.

Acre, one of the best defended cities of its day, was unable to withstand the powerful and well-organised assault, which made use of the most advanced weaponry then known. The trebuchet had truly made its mark. The days of the impregnable castle were well and truly over.

Gone but not forgotten

With the introduction of gunpowder, the trebuchet began to lose its place as the siege engine of choice to the cannon. One of the last recorded military uses was by Hernán Cortés, at the siege of Tenochtitlán in 1521. Its use was apparently motivated by the limited supply of gunpowder, but the attempt was reportedly unsuccessful. The first projectile landed on the trebuchet itself, destroying it.

In 2013, Syrian rebels were filmed using a trebuchet to project explosives at government troops in the Battle of Aleppo and the following year rioters used an improvised trebuchet to throw bricks and molotov cocktails during street riots in Ukraine.

Trebuchets compete in one of the classifications of machines used to hurl pumpkins at the annual pumpkin chucking contest in Sussex County, Delaware and there’s a trebuchet on a wine farm in South Africa that hurls cars around the place to amuse tourists.

Talking of chucking cars around, an episode of The Grand Tour last year showed the Top Gear team ostensibly trying to send a French model – car, that is – back across the English Channel by trebuchet because Jeremy Clarkson didn’t like the roof. Clowning around with a machine as powerful as a trebuchet could be bad for your health, but being adaptable to changing circumstances is the hallmark of a great invention!

References

http://www.primaryhomeworkhelp.co.uk/castles/defence.htm

https://military-history.fandom.com/wiki/Siege_engine

https://en.wikipedia.org/wiki/Battering_ram

https://en.wikipedia.org/wiki/Ballista

https://en.wikipedia.org/wiki/Onager_(weapon)

https://en.wikipedia.org/wiki/Trebuchet

https://en.wikipedia.org/wiki/Chinese_siege_weapons

https://en.wikipedia.org/wiki/Battle_of_Caishi

https://en.wikipedia.org/wiki/Siege_of_Jerusalem_(1099)

https://en.wikipedia.org/wiki/Siege_of_Toulouse

Dávid Márk Kotán, Medieval Stone-Throwing Siege Engines, Hungarian Archaeology E-Journal, 2017 Winter

https://en.wikipedia.org/wiki/Acre,_Israel

Black Camels and Blazing Bolts, Paul E Chevedden, American University of Sharjah, Mamluk Studies Review, Vol 8/1, 2004

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