Siege Techniques

The Siege at Antioch (1098)

Castles were built to attack towns or other castles. William of Normandy used four against Domfront in 1052 and built one for his successful siege of Arques in 1053–4. The army of the First Crusade constructed three at Antioch. In 1102, Raymond of Toulouse began the famous Mont Pèlerin on a ridge dominating the city of Tripoli, which only fell long after his death in 1109; thereafter, the increasingly elaborate castle served as a formidable redoubt of defence for the city. At Tyre in 1111, Baldwin I built a fortified camp for his besieging force. At Alençon in 1118, the citizens admitted Fulk of Anjou into the town and he constructed what the sources refer to as a “park”, an earthwork camp, as a base for his siege of the castle. Barbarossa built a camp for his siege of Manfred’s castle near Castelleone in 1186, and the place surrendered on terms. In 1247, Frederick II created the grandiosely named “city” of Victoria, but his army was surprised by the besieged Parmans and destroyed. A camp provided shelter for the besiegers, protected them and their equipment from sallies, and provided a logistic base, as witness the huge booty of food seized by the Parmans at Victoria. At the same time, there was an obvious coercive purpose: Victoria was built only four bow shots away from Parma. However, fortified camps were not an invariable condition of success: the First Crusade built none during the siege of Jerusalem. By contrast, during the Third Crusade very elaborate fortifications ringed the crusader camp before Acre. Sieges, especially of lesser castles, were often undertaken in a very casual way if no relief army was anticipated and the place was not strong, but bases were essential for operations against major fortifications.

There were a variety of stratagems for attacking fortifications. Wooden castles could be burned, although this was never as easy as we tend to think. An earthwork slope such as that of the motte made approach difficult – but not impossible, as the picture of Dinan in the Bayeux Tapestry shows. Setting fire against timber was by no means easy: Raymond of Aguilers spoke of mallets set with spikes being hurled at crusader machines during the final attack on Jerusalem in 1099, and another source tells us that a “newly invented” machine threw fire at the assault by the Count of Toulouse. The sources make fairly frequent reference to “Greek Fire” being used by the Muslims at the siege of Acre. The availability of naphtha and other oil derivatives in surface deposits probably explains why such fire-throwing was more common in the Middle East than in the West, where creating any form of “sticky fire” that could adhere to a wooden palisade and ignite it must have been difficult – and almost impossible in wet weather.

A frequent stratagem was to undermine or batter down a wall with a ram or picks under the cover of showers of missiles. The approach of the attackers could be protected by mantlets, large panels of woven light wood. Armoured roofs or penthouses could be constructed, most simply of heavy logs leant against the defending wall, to shelter men working below. Alternatively, the roof could be mounted on wheels: such structures might be called “cats” or “sows”. At Nicaea in 1097, most assaults were delivered by penthouses, some of which sheltered battering-rams. A battering-ram, used to break through the outer wall of Jerusalem in 1099, was then burned to make way for the siege-tower that was brought up behind it to dominate the main wall. Battering-rams suspended in siege-towers were used at Tyre in 1111–12, but the defenders used grappling irons and ropes to foil them. At Acre during the Third Crusade, a great ram protected by a penthouse was deployed, but the Muslim garrison managed to burn it. Edward I used a ram at Stirling in 1304. Penthouses could be employed to cover troops approaching a wall and to provide fire-cover: at the first siege of Toulouse in 1211 “cats” of boiled leather supported the attackers. An enormous wooden penthouse, massively armed, led the final abortive attack in 1217, in the course of which Simon de Montfort was killed.

Deep mining was an alternative approach to undermining city or castle defences. Zengi seized Edessa in 1144 by undermining the walls using a system of natural tunnels. At Rochester in 1215, part of the curtain wall and then the southeast corner of the keep were undermined by a deep sap created by miners: in the case of the latter, the props in the sap were burned with the aid of the fat of 40 pigs. At Bedford, too, in 1224 the inner bailey and the keep were mined. In the Holy Land, both Crac des Chevaliers in 1271 and Marqab in 1285 fell to mining operations. But the success of deep mining depended on soil conditions: at Dover the soft rock made for easy progress and reduced the need for careful propping, but the miners with Edward I in Scotland in 1300 were of little use in the siege of marshy Caerlaverock. At Acre during the Third Crusade, countermining blocked French attempts to bring down the walls. At Bungay castle in Suffolk, a mine and a countermine, dating from 1174, are intact. At Alessandria, Barbarossa’s “cat” covered the filling in of the ditch, supported a siege-tower and served to cover deep mining, but the defenders managed to collapse the tunnels. Even when mining was successful, the results were not always decisive; at Nicaea the breach was made late in the day and filled in overnight, while at Dover and Acre defences were improvised after breaches were made. Mining was also relatively slow and demanded skilled labour, which might not be available. Moreover, fortifications could incorporate design features to prevent it. Heavy batters in front of the wall could cause shallow mines to collapse before they reached anything vital, while cisterns could be sited across likely lines of sap, offering the possibility of flooding diggings. Overall, however, mining was the most consistently successful tactic used against fortifications.