Besiegers scaling walls from movable belfry
The great siege-engines, capable of shooting stones or bolts, which were often heated red-hot in an oven before delivery, from a considerable distance, did their work from the background. The men who looked after them were protected by a palisade, placed in front of the engines; this was the case with Philip’s engineers at Château-Gaillard. These machines are often indiscriminately called “stone-throwers” (petrariae, pierrières) or catapults; and accounts of them differ very considerably. It is clear that, in Roman and Byzantine warfare, the two main types of engine were the stone-throwing machine, known later as the mangon or mangonel, and the machine for shooting javelins, known as ballista.[90] The first consisted of an upright flexible beam between two solid upright posts. Cords were stretched from post to post and wound round the beam. The beam was then drawn back with the aid of winches and a stone placed in a hollow in its head; it was then suddenly let go, so that the twisted cords slackened, and the stone flew towards its mark, describing a high ellipse in its flight. The force by which the ballista was worked, depended, not on twisted cords, but on the tension of the cord which joined the two extremities of a great bow, and was attached to the movable grooved piece in which the javelin was placed. The tension released, the javelin was discharged. While the ballista could be discharged with a definite aim, the aim of the stone-throwing machine could be only general, and its chief use was to cast stones which, by their elliptic flight, dropped inside the walls of the besieged place.[91]
Engine for shooting javelins
Stone-throwing engine
The ballista, which was simply a huge bow, capable of shooting enormous bolts by the tension of a horizontal cord, was developed upon a small scale into the cross-bow or arbalast, which could be carried and managed by one man. The cross-bow was invented, or at any rate re-invented, in northern Europe towards the end of the eleventh century, it was employed in the first Crusade, and struck the Byzantines as a novelty.[92] The development of the larger engines seems to have proceeded with a view to stone-throwing, and combinations of the machines mentioned above may have been employed for this purpose.[93] Viollet-le-Duc, in his elaborate reconstructions of siege-machines, shows, for example, a mangon with a central upright post, working on a pivot, in a slot near the top of which is fixed a javelin. This post is strengthened by two diagonal beams fixed to the back of the framework, which moves on the same pivot, at the foot of the machine. Between these the flexible beam which propels the javelin is fastened by a cord working through a pulley to a winch turned by a man, and a bundle of cords is tightly twisted round the central post and the beam ([74]). He also shows a large stone-throwing engine on a wheeled carriage, which, in addition to an apparatus of twisted cords held in place by a system of ratchet wheels, and bound round the movable beam, has a cord stretched round the back of the beam, and connected with two huge springs forming a bow. The centre of the bow is a massive upright framework of wood, which acts as a buffer to the beam, when it is allowed to fly forward and discharge the stone ([74]). Minute as these reconstructions are, they seem to improve upon the data supplied by medieval writers and the pictures in MSS. Guillaume le Breton, the panegyrist of Philip Augustus, describes the stone-throwing machine used at the siege of Boves in 1185, as a great sling worked by several men, which threw immense rocks of great weight. The beam to which the projectile was attached worked on an axis, and was dragged backwards to the ground with ropes, and then set free.
Trébuchet or Slinging machine
