On November 27, 1095 at Clermont in France, Pope Urban II inaugurated the bloody period of history known as the Crusades, with the rousing cry, "Deus vult" meaning God wills it. Knights, nobles and ordinary citizens of France, Germany and Italy were first to respond, mobilizing to re-take the Holy Land from its Muslim rulers.
With each military campaign, stretching from the First Crusade of 1095-1099 until the thirteenth century, the European armies enhanced and perfected their use of siege weapons. Such devices had existed since ancient times, but with the development of stone castles and citadel walls, an attacking force needed powerful weapons to breach enemy fortifications.
Sieges could seem like never-ending contests of wills. At varying stages, the defenders of the Holy Land lost or held out against increasing attacks by the Crusaders. For both sides, morale as much as an adequate supply of food and water determined the outcome. Neither would have wanted a prolonged siege, risking desertion, disease and the loss of resources. Most sieges began after an unsuccessful attempt to take an area.
After negotiations for surrender failed, each side had ample time to prepare for a siege. For the Crusaders, it meant assessing the weakest section of a defensive wall, but it also allowed those behind the wall time to prepare. There were three methods to breach a site; to tunnel under its walls, climb over them or to knock them down. The sandy ditches around citadels in the Holy Land didn't always allow the attackers to undermine walls at their bases, so that often meant going over them or through them.
During the First Crusade, Christian armies relied on towers. At the seven-month Siege of Antioch (October 1097-June 1098), the Crusaders used three towers in their attacks against this Syrian city. Under the control of Byzantine Emperors for centuries, Antioch fell to the Muslims in 1085. Its capture would allow the Crusaders to move on to their ultimate prize--Jerusalem. Constructed of timber, and mobilized on wheels or rollers, the rectangular siege tower allowed attacking armies to advance on a defensive castle wall, under some protection from enemy arrow fire.
At the site, engineers built the towers to an equivalent height of the wall their army wanted to scale. Inside, there were several storeys, reachable by ladders. They covered the wood with animal hide to protect from flaming arrows. The army pushed the tower toward the wall and when it was judged close enough, they extended a platform to abut the wall, allowing them to rush across the top of it, or to scale ladders to its height. Archers inside kept the defenders from getting too close, but not always.
Antioch did not submit to the Crusaders because of their siege; it fell by treachery from inside the walls. The European armies recognized that siege towers were vulnerable to fire and determined defenders could quickly put an end to any intrusion by setting them ablaze. They needed another way to breach enemy walls while minimizing the casualties sustained in an attack. One method of doing so involved the refinement of the ancient catapult system to batter down walls.
Two types of artillery weapons were particularly important in Crusader assaults on the Holy Land; the mangonel, primarily a stone-throwing machine and the counterpoise trebuchet, which used gravity and a sling method to hurl any kind of projectile. Both siege machines had their origins in earlier history but were used to devastating effect in the medieval period. The mangonel had a bowl-shaped bucket at the end of its wooden throwing arm and maneuvered on wheels. Ropes attached to the arm were twisted to provide the torsion. An attacker placed projectiles, usually stones, into the bucket from which they were thrown up to a distance of over a thousand feet.
But the mangonel had its limits. The amount of weight used was limited by a person's strength and this in turn, reduced the damage that might be done . The counterpoise trebuchet eliminated this problem. While the mangonel's design allowed it to smash through masonry or rock, the trebuchet's projectiles were sent through walls or over them.
One of the most accurate developments of the catapult system, the trebuchet had a greater throwing distance and was more powerful than the mangonel. With its sling and arm swing mechanism, armies used the trebuchet to terrify their enemies, including hurling dead animals or people over the walls. At the Sieges of Acre and Jerusalem, the Crusader kings relied on these devastating machines of warfare, giving them nicknames, "Bad Neighbor" and "God's Own Catapult" as they sought to wrest further control of the Holy Land from the Muslims or keep the regions they captured in earlier warfare.
Siege weapons were costly and required skilled engineers for their design, a sizable force for their construction and dismantling, and the materials for building them. Their use shaped the balance of power in the Middle Ages for centuries until the introduction of more advanced methods of warfare.