Pt10
The counterweight-trebuchet appears so suddenly that it was evidently an invention. Its creation must have been the outcome of careful thought and calculation, because performance depended on a number of variables, notably the shape of the hook that governed the release of the sling, the weight of the missile, the weight of the counterpoise, the ratio between the parts of the arm and the length of the sling. But formidable though it was, the counterweight-trebuchet did not radically alter the balance of advantage between attack and defence. Walls were built more strongly, and at Kenilworth, and later Caerphilly, the creation of large ponds around the main fortifications kept the weapon out of range.
The construction and operation of the counterweight-trebuchet was the province of specialist engineers, who were not always available, and it was ponderous to transport. Its use was, therefore, limited, and traction-trebuchets remained popular because they were simpler and cheaper. The weapon had a limited range: trials on modern replicas suggest that it was of the order of 100–120m, but at this distance projectiles would be striking the bases of walls rather than their weaker upper parts. Counterweight-trebuchets were deployed so close to their targets that the operators needed protection from the missiles of the defenders: the machine used against Dryslwyn and Newcastle Emlyn had a shelter to protect them.
The dynamics of the traction-trebuchet are so complex that it must have been very difficult to change range. For example, a lighter missile will only go further if adjustments are made to the sling and the hook. The operator must have had to make very careful judgements balancing range against weight of missile, and taking into account local topography, weather and the strength of the target, in order to locate the machine; once in situ it was unlikely to be moved. Moreover, the quality of the missiles mattered. At Castelnaudary, stones that would not shatter had to be brought from “a long league away”; even so, one of them shattered, limiting damage. At Acre, Richard used very hard stones brought from the West, which were so unusual that they were specially shown to Saladin.
Moreover, the counterweight-trebuchet could also be as useful to the defender as to the attacker. We have noted that traction-trebuchets were deployed on towers that gave them enhanced range. Counterweight-trebuchets could be built within the walls. At Toulouse, Simon de Montfort’s great “cat” was smashed by a stone from a counterweight-trebuchet, and he was killed by one thrown by a traction-trebuchet, allegedly worked by women. An illustration of the siege of Savona by the Genoese in 1227 shows a traction-trebuchet on the city wall being struck by a stone from a much larger machine fired by the attackers, and there is a similar picture in a manuscript of Peter of Eboli.
In the Muslim East, enormous towers began to appear in the fortifications of the thirteenth century in order to carry counterweight-trebuchets: the most obvious example is the great square structure known as Baybars’ Tower, which dominates the vulnerable southern wall of Crac des Chevaliers. The square towers at Bosra and the enormous round ones at Subeibe had the same function. This seems to reflect a much greater use of heavy missile-throwers in siege-warfare in the Middle East than in the West. Baybars even dragged such equipment up the terrible slopes of ’Akkar in 1271 after his success against Crac. At Acre in 1291, al-Ashraf deployed nearly 100 machines, including a great trebuchet called “The Victorious”: this was siege-warfare on a scale unknown in the West.
