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The Word Pierrier denotes a stone throwing device and is used as a general term to cover a number of different types of war engine.

Pierriers were employed either to smash masonry walls or to throw projectiles over them.

All pierriers were made from wood. With the introduction of gunpowder, the pierrier ceded its place as the siege engine of choice to the cannon. Specific types of pierrier are:

Traction Trebuchets Edit

The trebuchet derives from the ancient sling. A variation of the sling contained a short piece of wood to extend the arm and provide greater leverage. This was evolved into the traction trebuchet by the Chinese, in which a number of people pull on ropes attached to the short arm of a lever that has a sling on the long arm. This type of trebuchet is smaller and has a shorter range but is a more portable machine and has a faster rate of fire than a larger counterweight powered one. The smallest traction trebuchets could be powered by the weight and pulling strength of one person using a single rope; but most were designed and sized to need from 15 to 45 men, generally two per rope. These teams would sometimes be local citizens assisting in the siege or in the defence of their town. Traction trebuchets had a range of from 2000 to well over 3000 feet when casting weights up to 750 pounds (60 kg). A traction trebuchet functions in the same way as a counterweight trebuchet, except that instead of a hoisted weight, the hurling arm is powered by a crew of men, pulling on ropes attached to the short lever arm. A counterweight trebuchet is powered by a very heavy counterweight, acting on a lever arm. The fulcrum of the lever (usually an axle) is supported by a high frame, and the counterweight is suspended from the short arm of the lever. The sling is attached to the end of the long arm of the lever. One end of the sling is captive, while the other end is hooked to the long arm in such a way as to release when the arm and sling reach the optimal hurling angles. The trebuchet is energised by lowering the long arm and raising the weighted short arm, usually with a winch, and is locked into the charged state by a trigger mechanism (cocked). With the long arm lowered near ground level, the sling is loaded with the projectile, and laid out on the ground, with the captive and hooked ends away from the target, and the load and pouch laid on the ground toward the target, under the trebuchet. When the trigger is released, the weighted short arm is driven by gravity into an accelerating pendulum motion, causing the lighter, long arm of the lever to revolve around the fulcrum at the opposite arc, which in turn, pulls the sling and its contents into a whipping motion at the end of the long arm. As the arm continues to swing past the vertical position, the counterweight rises, causing the lever motion to begin to slow down, while the sling continues to whip forward around the end of the long arm. When the sling reaches its launch angle, one end slips from its hook, releasing the projectile toward the target.

It is believed that the first traction trebuchets were used in China as early as in the 5th century BC, descriptions of which can be found in the 5th century BC. The traction trebuchet next appears in Byzantium. The Strategikon of Emperor Maurice, composed in 539, calls for "ballistae revolving in both directions," , probably traction trebuchets. The Miracles of St. Demetrius, composed by John I, archbishop of Thessalonike, describe traction trebuchets in the Avaro-Slav artillery: "Hanging from the back sides of these pieces of timber were slings and from the front strong ropes, by which, pulling down and releasing the sling, they propel the stones up high and with a loud noise."

Counterweight Trebuchets Edit

The counterweight trebuchet appeared in Christian and Muslim lands around the Mediterranean Sea in the twelfth century. It could fling three hundred pound (140 kg) projectiles at high speeds, at times including corpses infected with various diseases including the black plague, in an attempt to infect the people under siege, as a medieval variant of biological warfare. Trebuchets were far more accurate than other forms of medieval catapults. Our first clear written record of a counterweight trebuchet comes from an Islamic scholar, Mardi al-Tarsusi, who wrote in 1187, "Trebuchets are machines invented by unbelieving devils." (Al-Tarsusi, Bodleian MS 264).

At the Siege of Acre in 1191, Richard the Lionheart assembled two trebuchets which he named "God's Own Catapult" and "Bad Neighbour". During a siege of Stirling Castle in 1304, Edward Longshanks ordered his engineers to make a giant trebuchet for the English army, named "Warwolf". Range and size of the weapons varied. In 1421 the future Charles VII of France commissioned a trebuchet (coyllar) that could shoot a stone of 800 kg, while in 1188 at Ashyun balls up to 1,500 kg were used. Average weight of the projectiles was probably around 50-100 kg, with a range of ca. 300 meters. Rate of fire could be noteworthy: at the siege of Lisbon (1147), two engines were capable of launching a stone every 15 seconds.

The largest trebuchets needed exceptional quantities of timber: at the siege of Damietta, in 1249, Louis IX of France was able to build a stockade for the whole Crusade camp with the wood from 24 captured Egyptian trebuchets.

The lever must be as light as possible for maximum acceleration, yet strong enough not to break under the stress. The ratio of the length of the long to the short arms of the lever, and to the sling length, are important factors in determining the range of the projectile. The object of a good design is to transfer as much energy as possible from the falling counterweight into the projectile. The maximum range for a hypothetical 100% energy transfer, R, of the projectile can be shown to be R = 2hM /m, where h is the distance the counterweight falls, and M and m are the mass of the counterweight and projectile, respectively. The efficiency of a real trebuchet is the ratio of the actual range achieved to the calculated maximum range.

There are no really detailed descriptions of medieval or earlier trebuchets that give the dimensions or shape of the beam, the ratio of its long arm to its short arm, and so on. No specimens or models from medieval times survive. The few extant contemporary drawings of them are highly schematic and sometimes show physically impossible proportions. Methods used for optimising their performance and design were apparently closely held military secrets.

Placing and aiming the trebuchet was also, no doubt, done by empirical trials. Small adjustments could be made by changing the angle of the hook holding the free end of the sling, a process which requires a heated forge on a full-scale engine. For larger, quicker adjustments, the length of the sling can be altered. Small adjustments from side-to-side can also be made by moving the channel in which the missile and sling slide in the base of the frame. The trebuchet itself could be moved as well, but with larger trebuchets, this would have been difficult; the largest trebuchets could weigh many tons.

Because of the time required to load the sling and to raise the counterweight, a large trebuchet's rate of fire was slow, perhaps not more than a couple of shots an hour. This was due both to their size and the mass of their counterweights. Smaller trebuchets can fire a couple of times a minute. The payload of a trebuchet was usually a large rounded stone, although other projectiles were occasionally used including dead animals, beehives, the severed heads of captured enemies, small stones burned into clay balls which would explode on impact like grapeshot, barrels of burning tar or oil, Greek fire, pots of burning lime, unsuccessful ambassadors, prisoners of war, hostages, and captured spies.

Trebuchets were powerful weapons, with a range of up to about 300 yards/ 270 m. Castle designers often built their fortifications with trebuchets in mind; The range of many trebuchets was in fact shorter than that of a longbow in skilled hands, making it dangerous to be a trebuchet operator during a siege

A trebuchet can increase its efficiency by allowing the counterweight to take the straightest possible downward path. This maximises the transfer of the counterweight's potential energy to the projectile rather than to stressing the frame. Mounting the counterweight on a pivot (below top) straightens the path of its fall, increasing its effectiveness. A fixed counterweight trebuchet in particular can therefore be made more efficient by the addition of wheels to allow the frame to move freely back and forth (below bottom). This also allowed the trebuchet to fire farther.

The addition of wheels also makes the trebuchet more stable as part of the forward momentum of the falling counterweight is transferred to the forward motion of the trebuchet instead of a tilting action of the vertical frame, possibly tipping over of the machine or severely damaging the structure. The velocity of the trebuchet frame is added to that of the item being thrown, increasing its velocity and range by up to 33 percent. The wheeled trebuchet can effectively employ a fixed counterweight, mounted to the short end of the throwing arm, rather than the pendulum weight described above. The weights were usually stones and rubble, since lead was far too expensive and could be used for better purposes in a siege.

That of dead, and often partially decomposed, carcasses of animals or people. These were used to intimidate the defending force, lower their morale, and often to spread disease amongst the besieged. This tactic often proved effective as the short supply of food, which was often of low quality or rotting, combined with the cramped living space of the defenders, poor hygiene, and infestations of vermin (which made convenient vectors for disease) made the ideal scenario for the spread of disease. Burning sand also could have been thrown at enemies. This has the effect of sand sticking in armour holes, which leads to a most painful burning or death.

Despite its low accuracy, the versatility and manoeuvrability of the mangonel ensured that it was the most popular siege catapult used during the medieval period.The Counterwieght of a trebuchet

Onagers and Mangonels Edit

The onager was a post-classical Roman siege engine. Its name comes from that of an onager (a wild jack ass), the similarity being its violent kicking action. The onager was a type of catapult that used torsional pressure, from twisted rope, to store energy for the shot. It consisted of a frame placed on the ground to whose front end a vertical frame of solid timber was rigidly fixed. Through the vertical frame ran an axle, which had a single stout spoke, on the extremity of which was a sling used to launch a projectile. In action the spoke was forced down, against the tension of twisted ropes or other springs, by a windlass. It was then suddenly released. The spoke kicked the crosspiece of the vertical frame, and the projectile at its extreme end was shot forward. Onagers of the Roman Empire were mainly used for besieging forts or settlements. They would often be armed with huge stones or rocks that could be covered with a flammable substance and set alight. The Romans greatly improved the onager's manoeuvrability by adding wheels to its base. The wheels and the onager's light weight made it easy to move.

In the Middle Ages (recorded from around 1200) a less powerful version of the onager was used that held the projectile in a fixed bowl instead of a sling. This was so that many small projectiles could be thrown rather than one large one. This engine was sometimes called the mangonel, although the same name may have been used for a variety of siege engines.

A mangonel was a type of catapult or siege machine used in the medieval period to throw projectiles at a castle's walls. The mangonel did not have the accuracy or range of a trebuchet and threw projectiles on a lower trajectory than the trebuchet.

The mangonel was a single-arm torsion catapult that held the projectile in a sling. A similar and perhaps older device was nicknamed the scorpion because of its resemblance to a scorpion's tail and sting.

The word mangonel is derived from the Greek word 'magganon' which means "an engine of war", but was first used in medieval accounts of sieges.

Mangonels shot heavy projectiles from a bowl-shaped bucket at the end of the arm. The bucket was used to launch more rocks than a sling could; this made it different from an onager. In combat, mangonels hurled rocks, burning objects (or vessels filled with flammable materials which created a fireball on impact; fire pots), or anything else readily available to the attacking and defending forces. One of the more unusual types of projectile was

Ballistas and Springalds Edit

The balista seems to have died out with much other technical know-how when the Roman Empire became Christian and learning was heavily discouraged (Everything a good Christian needed to know was in the Bible). The technology was rediscovered in the late middle ages when an exception was made for military engineering.

Bombards Edit

A bombard is a large calibre, muzzle-loading medieval cannon or mortar, for throwing heavy stone balls. The name bombarde was first noted and sketched in a French historical text around 1380. The modern terms bomb and bombardment derives from this.

Bombards were usually used during sieges to hurl various forms of missile into enemy fortifications. Projectiles such as stone or metal balls, burning materials and weighted cloth soaked in quicklime or Greek fire are documented.

The name derives from medieval Latin and French forms from a Greek word expressing the making of a humming noise.

A notable example of a bombard is the large Mons Meg weapon, built around 1449 and used by King James II of Scotland. It was very powerful used for bringing down castle walls. Mons Meg was capable of firing 180 kg (396 lb) shots and was one of the largest bombards in its time. It is now housed on public display at Edinburgh Castle.

Other known 15th century superguns include the wrought-iron Pumhart von Steyr and Dulle Griet as well as the cast-bronze Faule Mette, Faule Grete, and Grose Bochse. The Tsar Cannon is a late 16th century show-piece.

The Dardanelles Gun, built in the Ottoman Empire in 1464 by Munir Ali, with a weight of 18.6 t and a length of 518 cm, was capable of firing stone balls of up to 63 cm diameter.

Eventually bombards were superseded by weapons using smaller calibre iron projectiles with more powerful gunpowder.

Petards Edit

A petard was a small bomb used to blow up gates and walls when breaching fortifications. The term has a French origin and dates back to the sixteenth century. In a typical implementation, it was commonly either a conical or rectangular metal object containing 5 or 6 pounds of gunpowder, activated with a slow match used as a fuse. The word petard comes from the Middle French peter, to break wind, Petard remains a French word meaning a firecracker today (in French slang, it also means inter alia a handgun).

The word remains in modern usage in the phrase hoist with one's own petard, which means "to be harmed by one's own plan to harm someone else" or "to fall into one's own trap", literally implying that one could be lifted up (hoist, or blown upward) by one's own bomb.

Petards were often placed either inside tunnels under walls, or directly upon gates. When placed inside a tunnel under a wall and exploded, large amounts of air would often be released from the tunnel, as the tunnel collapsed. By securing the device firmly to the gate, the shape of the device allows the concussive pressure of the blast to be applied entirely towards the destruction of the gate. Depending on design, a petard could be secured by propping it against the gate using beams, or nailing it in place by way of a wooden board fixed to the end of the petard in advance.

If a petard were to detonate prematurely due to a faulty or short slow match, the engineer would be lifted or "hoist" by the explosion. William Shakespeare used the now proverbial phrase "hoist with his own petard" in Hamlet.

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