Pt7
Artillery capable of battering fortifications and defenders into surrender, known in Roman times, continued to be used.
At the siege of Paris in 885– 6, mangana, catapulta and balistae are mentioned as hurling missiles. But these are only a few of the bewildering variety of words used by medieval writers to refer to siege engines. Unfortunately, their use is inconsistent and such descriptions as they give are confusing.
Orderic tells us that at Brévol in 1092 a great machine was rolled up to the wall, which suggests a tower or penthouse, but adds that it hurled stones: it is possible that this was some kind of platform that accommodated a stone-thrower. Otto of Freising refers to a mangonel as a kind of balista, although this was a quite different kind of machine. The word petraria, rendered as perrier in French, is often used but this merely means a stone-thrower. William of Tyre and Guillaume le Breton both clearly suggest that perriers were for heavy bombardment while mangana were lighter anti-personnel weapons, and the same notion about the latter is found in the Chanson de la Croisade Albigeoise.
Mangonella would seem to be only a diminutive of mangana; in Roman times this referred to a weapon that depended for power on torsion. The mangana was a machine with a single arm, whose bottom end was embedded in a massive horizontal winding of sinew: the arm was bent back against the torsion of the winding and, when released, flew forward against a robust frame, hurling a stone out of a cup or sling on its end. The crash of impact between arm and bar probably explains the nickname onager, “the mule”, for this machine. The missile was thus launched in an arc like the shell from a howitzer.
The Roman balista was a crossbow-like weapon, but the “bow” consisted of two arms, each mounted in a vertically wound gathering of sinews, which provided the tension when the string was drawn to fire a bolt or ball: its trajectory would have been flat. The term balista in medieval sources generally refers to crossbows. Clearly related was the arcu-balista or later springald, a flat-trajectory weapon rather like a giant crossbow, which was widely used in sieges.
The traction-trebuchet was the dominant form of artillery in our period. It was a device that originated in China and was transmitted to Europe by about the ninth century via the Arab world. It was essentially a beam pivoted between two high uprights: when the beam was pulled at one end by a team of men, the other flew up until a missile was released in an arcing trajectory either from a cup or, more effectively, from a sling. The pulling end of the beam was by far the shorter, in a ratio of perhaps 1: 5, and the efficiency of the engine was enormously enhanced by the use of a sling on the throwing end. This kind of lever artillery varied in size, which partly accounts for the inconsistency of the language used to describe it; broadly, it would seem that petraria and mangana indicate sizeable examples and mangonella and tormenta lesser ones.
There is no reason to believe that the principle of torsion was forgotten, but the impact of the throwing beam must have put enormous strain on the structure of the onager, which would have had to be very heavy to last any time, and of extraordinary size and weight to throw a large missile: lever-action machines were probably lighter and more durable. Moreover, the technology of lever-artillery could be easily assimilated by a society in which increasingly complex machinery, such as water mills with pivoting wheels and gears, was becoming common. At the siege of Jerusalem in 1099, both Albert of Aachen and Tudebode report that the crusaders used machines powerful enough to throw captured spies into the city; in the case cited by Tudebode, the machine had a sling, which, together with the presumed power, strongly suggests a traction-trebuchet and implies that they were not a novelty.
