Essay On Trebuchet

In June 1210, Count Simon de Montfort besieged two hundred knights, priests, and citizens within the fortress of Minerve as part of his campaign throughout southwestern France to eradicate the Cathar heresy. Considered impregnable, Minerve stood atop a daunting limestone cliff 246 yards above the Cesse River in the region known as the Languedoc. De Montfort knew that with ample provisions and an internal water source, Minerve’s defenders could outlast any siege, and he had no patience.

Within days his engineers had built a towering siege engine: an oversized balance beam with a weighted bucket at one end called a trebuchet — a relatively new arrival on the European battlefield. The walls of Minerve were beyond the reach of this piece of medieval

artillery, but that didn’t matter. Hurling stones weighing nearly a ton, the machine began a steady pounding of the cliff face, literally shaking the mountain beneath Minerve so vigorously that the well shaft within collapsed. In the sweltering days of summer, the defenders had no choice but surrender.

It is unclear who christened this particular war machine with the nickname Malvoisine (‘the bad neighbor’).

Obviously, soldiers on both sides of Minerve’s walls gave the trebuchet ample respect.

The word trebuchet comes from the Middle French verb trebuch, meaning ‘to tumble’ or ‘to fall over,’ which is exactly what the throwing arm of a trebuchet does when it is released. The medieval etymology of the word (first appearing in English in the fourteenth century as ‘trepegete’) has led many historians to believe that this war engine was a medieval invention, but this ‘bad neighbor’ took up residence in the annals of military history long before that.

Stone-throwing artillery was hardly a new idea in the thirteenth century. Both the Greeks and Romans employed engines to fire stones and darts at their enemies. In the ancient world, however, war engines were powered either by torsion (a wound rope, such as in the Roman onager) or tension (a drawn bow, such as in the Greek oxybeles). The trebuchet was the first war engine to employ the principles of gravity and leverage to hurl a

projectile.

Renaissance and Enlightenment scholars considered this transition from the complex war machines of the ancient world to the comparatively simple design of the medieval trebuchet as proof of the superiority of classical knowledge. More recent investigation, however, has revealed that the trebuchet’s simplified design offers significant advantages over its more technically complex forebears.

Lacking any components capable of achieving high-energy states of elasticity, the trebuchet was not subject to the catastrophic failures that plagued earlier machines if they were not fastidiously maintained. Whereas torsion and tension engines required numerous precision-made parts — such as metallic gears, locks and frames — a trebuchet could be constructed in the field almost entirely out of rough-cut lumber and using natural stones. Siege engineers, masters of adaptation, seem to have recognized a superior design when they saw it.

The earliest incarnation of this type of artillery was the traction trebuchet or perrier, a type of rotating-beam engine powered by the most readily available form of ballast imaginable: human beings. A team of haulers pulled down on a network of ropes attached to the rear of the machine’s throwing arm to operate a traction trebuchet; an engineer stationed at the front of the throwing arm loaded ammunition into the firing cup or sling. The engineer could also provide a bit of extra ‘whip’ to the machine’s action by adding his own weight to the throwing arm to retard its movement momentarily as the crew began its release. (Several historical illustrations, such as those in the Maciejowski Bible, show gunners dangling off the ground in such an effort.)

Oriental tacticians were using these machines to great effect as early as the fourth century b.c. The Chinese military treatise Wu Jing Zong Yao described traction trebuchets ranging in size from a quick-firing two-man model to one called the ‘whirlwind’ employing a pulling team of 250 and capable of firing a stone weighing 140 pounds more than eighty yards.

Arab and Islamic traders spread knowledge of the traction trebuchet beyond the Orient. By the sixth century a.d., the armies of Byzantium and the Middle East were using these machines in their military campaigns. Archbishop John of Thessalonike described a battery of fifty traction trebuchets called petrobolos (‘city-takers’) in his eyewitness account of the siege of that Macedonian city in 597. He claimed these machines flung so many stones that ‘neither earth nor human constructions could bear the impacts.’

The traction trebuchet offered an impressive rate of fire: A 1991 experiment conducted on a model made to ancient standards at the University of Toronto showed that a well-coordinated trebuchet crew could fire four rounds per minute. Yet the traction trebuchet was not without its shortcomings. As this experiment revealed, the logistics of coordinating a team of more than twelve pullers was very difficult, and the unavoidable mechanics limited the throwing arm to only a small fraction of its rotational potential.

Perhaps these limitations inspired engineers of the Near East and Mediterranean to upgrade the traction trebuchet design. They attached a weight to the short end of the throwing arm, resulting in an engine known as the hybrid trebuchet. The counterweight, possibly an iron plate forged directly to the short end of the pivoted beam, extended the range of the machines. Attaching a sling to the longer end of the beam and adding wheels that allowed the trebuchet to gain the full advantage of motion made it possible for war engines to sling a rock against a castle wall with accuracy.

Although hybrid trebuchets may have been known as early as the eighth century, documented evidence indicates this design was gaining widespread acceptance among Arab and Byzantine armies during the eleventh and twelfth centuries.

The Byzantine chronicler Anna Komnene alluded to this emerging technology when she mentioned several ‘unconventional engines’ that were employed at the siege of Nicaea in Asia Minor in 1097, which she claimed ‘amazed everyone’ with their ability to hurl gigantic stones. In the military vernacular of the eleventh-century Islamic world, the hybrid trebuchet was al-Ghadban, or ‘the furious

one.’

In a military manual written for Saladin in 1187, Arabic engineer Murdi ibn Ali ibn Murdi al-Tarsusi depicted a hybrid trebuchet that he said had the same hurling power as a traction machine pulled by fifty men due to ‘the constant force [of gravity], whereas men differ in their pulling force.’ (Showing his mechanical proficiency, Tarsusi designed his trebuchet so that as it was fired it cocked a supplementary crossbow, probably to protect the engineers from attack.)

Improved firing power was certainly the primary advantage of the hybrid trebuchet. Such a machine used at the siege of Damietta in Egypt in 1218 fired stones weighing four hundred pounds at the city walls.

Nevertheless, if a trebuchet powered by a small counterweight was good, then one with a large counterweight would be even better. As European engineers adopted the trebuchet and improved it in the eleventh, twelfth, and thirteenth centuries (after encountering these machines during the Crusades), this premise was taken to its logical conclusion by developing the counterpoise trebuchet.

Unlike traction and hybrid trebuchets, there was no need for human intervention in operating of the counterpoise trebuchet. These machines, powered by either stationary weights, or by hanging buckets filled with sand, rocks, or rubble from the short end of the beam, used gravity to far surpass the capacity of any crew of pullers. With no pulling team beneath the trestle, the sling could be laid in a launching trough directly under the pivot, creating a greater throwing arc. The centripetal acceleration and power of the counterpoise trebuchet could be enhanced by mounting the machine on wheels so it could move during the throw. Larger engines could sling rocks weighing a ton or more three hundred yards, hitting a castle wall with devastating force.

The counterpoise design elevated the trebuchet’s destructive power. At the siege of Castelnuovo Bocca d’Adda in Northern Italy in 1199, attackers used trebuchets that could fire stones weighing between nineteen hundred and twenty-five hundred pounds. European engineers who built these machines gave them nicknames such as ‘God’s stone thrower,’ ‘the daughter of the earthquake,’ ‘big mother,’ ‘war wolf,’ and the ‘bad neighbor’ that de Montfort used to attack Minerve. Islamic chroniclers who saw these trebuchets being used, described them simply as ‘manjaniq ifiranji‘ — Frankish war machines.

The improved firing capability of the counterpoise trebuchet came at a price, however. Such machines needed elaborate block and tackle systems to raise the heavy ballast box; they could only be fired three or four times per day, according to contemporary accounts. However, the power of the counterpoise design gave these war machines a new role in battle. Smaller trebuchets had been relegated to the tasks of supporting troops scaling castle walls or targeting structures within a walled city; counterpoise trebuchets could actually be used against the walls themselves, thus sparking an architectural arms race that would continue well into the gunpowder age.

Not until modern times did the cannon eclipse the trebuchet. The strategist Christine de Pizan, in her book Fais d’armes et de chevalerie written for the Duke of Burgundy in 1410, explained that even an army equipped with sizable ‘gonnes’ should still have ‘four entirely new trebuchets, completely equipped, each one with two cables and four slings to change when needed.’

Moreover, trebuchets were not limited exclusively to use outside castle walls. In 1218, while preparing for an assault on the city of Toulouse, France, Simon de Montfort, the victor at Minerve, was struck down by a rock falling from the sky — a stone fired from a trebuchet inside the city. Even the most skilled general was not immune to the wrath of a bad neighbor.