Trebuchet

Origins

The trebuchet began in China as the traction engine: a beam on a pivot with a sling at one end and a crew of dozens hauling on ropes at the other, recorded by the fourth century BC. The design traveled west through the steppe peoples to the Avars and Byzantines by the late sixth century, and the Islamic world adopted it as the manjaniq. The decisive change — replacing the pullers with a falling weight — was made somewhere in the eastern Mediterranean in the twelfth century; Mardi ibn Ali al-Tarsusi described counterweight machines in a military treatise written for Saladin around 1187, and within a decade they were in use in Italy and across Latin Christendom. Gravity delivered the same force on every shot, so the new engine could be aimed, adjusted and scaled up in a way a crew of men could not.

Design & Construction

A trebuchet is a lever. The throwing arm, often a composite timber beam ten to fifteen meters long, rides on an axle carried by a massive trestle frame; the short end holds the counterweight, the long end a rope sling in which the stone sits in a trough under the machine. Winched down by windlasses or treadwheels and released by a trigger, the falling weight whips the arm upward, the sling swings through a longer arc still, and one end of the sling slips off a hook on the beam at the moment that sets the trajectory. Early machines used a fixed counterweight; the hinged box, which hangs and swings as it drops, gave a smoother and more efficient throw. Large engines threw stones of 50 to 150 kilograms roughly 200 to 300 meters, repeatedly into the same stretch of wall, and they also threw fire, carcasses and, at least once, the severed heads of prisoners. Everything was built on site by specialist engineers from local timber, and the stones were cut to matched weights so that range stayed constant.

Combat Use

Counterweight trebuchets were central to the sieges of the The Crusades: at Acre in 1189-91 Philip II of France battered the walls with an engine the crusaders called Bad Neighbour, while the defenders answered with one of their own, and a century later the Mamluk sultan al-Ashraf Khalil brought dozens of engines against the same city, where the Knights Templar made their last stand in 1291. Edward I of England built the enormous Warwolf at Stirling Castle in 1304 and refused to accept the garrison's surrender until he had seen it shoot. In the East, the Mongol Horde brought Muslim engineers to the Song fortress of Xiangyang in 1273, whose 'Muslim trebuchets' broke a siege that had lasted five years. Against the thin, high curtain walls of the twelfth century the trebuchet was decisive, and castle builders answered it with thicker walls, round towers and wider moats.

Legacy

Gunpowder ended the trebuchet's reign in the fifteenth century — a bombard like the Hand Cannon's giant cousins could do in days what a stone-thrower did in weeks — though Cortés still had one built, without success, at Tenochtitlan in 1521. It remains the most studied of medieval siege engines, and modern reconstructions, from those built for television documentaries to the working machines at Caerphilly and Warwick castles, have confirmed the chroniclers' range figures. For collectors the trebuchet survives mostly in illuminated manuscripts, carved stone shot recovered from castle ditches, and models; beside the Crossbow it is the defining weapon of the Great Helm era of warfare.