Pt6
An alternative approach was to build huge wooden towers to overawe the defences and enable others to attack them.
The Vikings attacked Paris with one in 885–6. At Verdun in 985, the siege-tower was dragged by ropes passed around stakes close to the city wall, so that the oxen were moving away from the enemy. In 1087, a Pisan and Genoese expedition employed similar towers to capture Pantelleria.
Such machines were not necessarily mobile. At the siege of Pont Audemar in 1123, Henry I built a tower, but it was only used to rain missiles into the castle, whose garrison had first to watch the burning of the town around them and the devastation of the countryside. At Coria in Spain in 1138, wooden towers acted as firing platforms, while at Bedford in 1224 the huge towers built for Henry III seem to have been used to mount various kinds of stone-throwers which deluged the walls with missiles. At Ma’arra on the First Crusade, the tower built by Raymond of St Gilles was clearly mobile, but its purpose again was to act simply as a fire-base to cover mining and assaults by ladder, which eventually carried the day. This was probably the intended purpose of the towers in the siege of Jerusalem in July 1099, but that of Godfrey was fortuitously brought up close to the wall and a bridge was improvised to make entry.
Fully mobile siege-towers with drawbridges to launch an assault became a feature of important sieges, notably in the Holy Land where they were pre-eminent in the capture of the Muslim cities of the coast. Barbarossa used them in Lombardy, and Edward I attacked Bothwell castle in 1301 with a tower that had been transported in sections and was covered in hides against fire. In the West, towers continued to be important right down to the invention of cannons. At Lisbon, the Anglo-Norman force brought up a tower some 28m high and when this was destroyed, they deployed another one, 25m high, apparently built and commanded by a Pisan engineer; this proved to be the final straw for the garrison, which surrendered.
Such devices had very obvious limitations. The ground might be very unfavourable, as at ’Arqa on the First Crusade, where the city walls crowned a steep slope. In southern Italy, the relative isolation of inland places may have made it difficult to get siege-machinery to them. Even where the ground was generally suitable, it had to be smoothed and often ditches obstructed the route to the walls; at Jerusalem, the Count of Toulouse paid one penny for every three stones cast into the moat by the southern wall, while at Tortosa in 1148 a huge ditch 43m wide and 32m deep had to be filled.
The clumsiness and weight of the towers meant that they needed to be built as close as possible to the point of attack. At Jerusalem in 1099, the defenders of the northern wall built up the walls, set up catapults and prepared beams and padding to repel the expected attack. The crusaders changed their assault point, and this was probably the decisive factor in the siege: near Zion Gate the Count of Toulouse had no room for manoeuvre and his tower was ultimately incapacitated by catapult attack and fire. A similar fate befell Bohemond’s tower in the attack on Durazzo in 1108.
Fire was the great enemy; the successful machine at Lisbon was covered with wet hides, with the animal tails hanging down for maximum flow, while at Jerusalem Godfrey’s tower was soaked in vinegar against the defenders’ “Greek Fire”. During the siege of Tyre, the defenders built a war-crane on the city walls, which overtopped the crusader siegetowers and destroyed them by dropping incendiaries on to them.
Siege-towers were remarkable structures, but they were not a certain solution to the problem of attacking fortifications. Terrain was often a problem and countermeasures by the besieged could destroy them. Above all, they were costly and justified only for major objectives.
