7 Powerful Medieval Weapons That Characterized Siege Warfare

Medieval war revolved around the sieges of castles and towns. In this article, we explore the terrifying medieval weapons that besiegers used to breach the walls of fortifications.

Jan 22, 2021By Jack Crawford, BA Medieval History, MPhil Anglo-Saxon, Norse and Celtic History
siege warfare weaponry
Details from The Siege of Lisbon by Alfredo Roque Gameiro, 1917; and Assyrian gypsum wall relief displaying Ashurnasirpal II besieging a strongly-walled town using a battering ram, 865-60 BC


Medieval war was primarily conducted as a series of sieges. Capturing castles was the key to conquering a region or territory because it represented the local seat of economic and political power. Castle garrisons could threaten an advancing army’s supply lines if they were bypassed, so sieges became the default method by which a medieval war would be conducted. However, assaulting and capturing a castle was no easy task, they were powerful defensive fortifications meticulously designed to resist attack. As a result, besieging medieval armies turned to a series of siege engines to give them an advantage. Below is a list of 7 medieval weapons used during siege warfare. 


Medieval Weapons for Breaching Fortifications


1. Battering Ram: Ancient Invention Used In Medieval War

wooden battering ram bulgaria
A reconstruction of a simple wooden battering ram at Baba Vida Castle in Vidin, Bulgaria, photographed by Klearchos Kapoutsis, 2009, via Flickr


The battering ram is a very simple siege weapon designed to break open the gates or walls of a fortification through repeated blunt blows. Battering rams usually consisted of a large log, which would be propelled against a gate or wall with a large amount of force – either by a team of people holding the log and physically swinging it, or else by being suspended in a frame by chains or ropes, from which it would be pulled back and released to swing forwards.


In order to better protect the soldiers operating the battering ram from the missiles of the defenders, the frame in which the ram was mounted was covered. Often this (usually wooden) canopy was also coated in wet animal hides in order to make it resistant to fire. Rams could also be ‘capped’, where the end would be fitted with a block of iron or steel sometimes shaped into an animal’s head, in order to make them more effective during medieval war.


Battering rams were popular because they were extremely quick and easy to construct, whilst also being very powerful medieval weapons. When brought to bear against wooden gates or stone walls (which were particularly prone to splintering or shattering) they could create cracks and eventually holes with repeated blows, allowing the besiegers entry to the fortification.

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relief ashurnasirpal besieging battering ram
Assyrian gypsum wall relief displaying Ashurnasirpal II besieging a strongly-walled town using a battering ram, 865-60 BC, via the British Museum, London


This siege weapon has very ancient origins. The earliest depiction is thought to be from 11th century BC Egypt, where engravings on a tomb show soldiers advancing towards a fortress under a roofed structure carrying a long pole. During the iron age, battering rams were used across the Middle East and the Mediterranean. Assyrian engravings demonstrate how large and advanced these siege engines had become by the 9th century BC, with battering rams being covered in wet hides.


Historical sources also attest to the use of battering rams by the ancient Greeks and the Romans, who employed them first in wars against the Gauls. The Roman writer Vitruvius mentions an innovation used by Alexander the Great, whereby the ram was supported by rollers rather than ropes or chains. These rollers would allow the ram to pick up more speed, hitting its target with more force and causing greater damage. Battering rams remained popular as medieval weapons and were used at some of the most important sieges of the era, including throughout the crusades and during multiple sieges of Constantinople.


2. Siege Towers: Movable Protection

the siege of lisbon alfredo roque gameiro
The Siege of Lisbon by Alfredo Roque Gameiro, 1917, via Medievalists.net


Siege towers were designed to transport besieging soldiers and ladders close to the walls of a fortification, whilst also protecting them from enemy bow and crossbow fire. Usually, the tower would be rectangular in shape and was constructed to equal the height of the walls it faced. Internally the siege tower would be fitted with ladders and a series of platforms rising up the structure on which soldiers could stand. The top of the siege tower was usually crowned by another open-air platform – typically archers or crossbowmen stood on this top platform and fired at the defenders as the tower approached the walls.


These medieval weapons were mounted on wheels so that they could be pushed to the walls. Much like the battering ram, the wooden sides of the siege tower were susceptible to fire and were therefore often coated in wet animal hides. During an assault, the siege tower would be rolled to the walls as the soldiers inside sheltered from enemy missile fire – once it reached the walls, a gangplank would be thrown down between it and the wall, either from the top platform or one of the internal platforms, allowing the attackers to access the curtain walls of a fortification.


francis grose illustration moveable siege tower
Illustration of pavisors and a moveable siege tower from Military Antiquities Respecting a History of The English Army from Conquest to the Present Time by Francis Grose, 1801, via Google Books


Thanks to their enormous size and weight, siege towers were very slow and were usually the target of garrison artillery fire. They were typically constructed on-site during the siege, and some were even built to contain internal battering rams too. Siege towers were also vulnerable to earthworks such as ditches and would need teams of men to prepare the way for them during an assault by filling in these ditches.


Like battering rams, siege towers also have ancient origins and were used extensively by the Egyptians, Romans, Assyrians, and Chinese. They were commonly used as medieval weapons, and their designs became increasingly large and complex – at the siege of Kenilworth Castle, a tower that could house 200 archers was constructed. However, the invention of gunpowder artillery rendered siege towers obsolete, as cannons were far more effective at destroying the curtain walls of a fortification. Since these guns could destroy walls with relative ease, towers were no longer required to transport troops over curtain walls.


Projectile Launchers


3. Ballista: Large Missile Launcher

reconstructed ballista carpenter oak
Reconstructed ballista, via Carpenter Oak


The ballista was an ancient siege weapon that was primarily used to fire large arrows or bolts but could also be used to launch stones at the walls of fortifications. A ballista was similar in appearance to a very large crossbow, but instead of using a horizontal bow held under tension, it used two levers with torsion springs. Torsion is the twisting of an object using torque.


The torsion springs of a ballista were made of several twisted ‘skeins’ – coiled yarn or twine, usually made of cotton. Into the springs were inserted two wooden levers, and the bowstring of the ballista would be attached to the ends of these levers. When the string was pulled back, the springs would be held under tension. When fired the springs would release a great deal of energy, firing whatever projectile the weapon was loaded with.


The ballista developed as a Greek invention and was known to have been employed heavily by Alexander the Great and his father Philip II. The Romans also adopted it and used it extensively throughout their history. Notably, they added winches and metal components to their ballistae in order to make them better able to withstand greater tension forces, and therefore make them more powerful.


ballista bolt tips
Ballista bolt tips, in the Braunschweigisches Landesmuseum


Thanks to its relatively simple design, the ballista could be modified to fire both large bolts and stones, making it useful in a siege scenario. The most powerful examples could fire projectiles up to 1,000 meters, although the effective range was likely much shorter. Thanks to their small size, they could also be mounted on siege towers.


Ballistae were certainly used as medieval weapons, although as resources became more scarce, they were used less, eventually becoming obsolete with the invention of the springald and trebuchet. However, the engineering concepts of the ballista survived in the 12th-century arbalest crossbow, which used a winch and steel elements to create greater tension.


4. Springald: Bolts And Greek Fire

medieval weapon springald drawing
Plan of a Springald from De Re Militari (On the Military Arts) by Roberto Valturio, 1472, via The Met Museum, New York 


The springald was a medieval weapon very similar in function to a ballista, except that it was built around a rectangular frame, with inward swinging arms. Just like the ballista, it used twisted skeins to power two bow levers or ‘arms’ that swung inwards inside the wooden framework of the springald. It could fire large bolts (often tipped with metal) as well as stones. Greek fire was also known to have been shot from springalds by the Byzantines.


There is very little archaeological evidence for springalds, although they are attested as having been used across Western Europe in written sources during the 12th and 13th centuries. Leonardo da Vinci also drew up designs for a springald. Several working replicas have been built, including a 2.4-meter-long example which was able to throw a bolt weighing 2.4 kilograms over 55 meters.


5. Catapult: Simple Projectile Launcher


The catapult was a highly popular siege engine throughout the ancient world and continued to be used as a medieval weapon before it was superseded by the trebuchet. A catapult functioned by releasing stored potential energy in order to throw a projectile, most commonly a stone or rock. Catapults could also fire flaming projectiles, and even rotting carcasses of animals, which could be used to spread disease and lower morale in a besieged town.


catapult diagram the antiquities of england and wales francis grose
Catapult diagram from The Antiquities of England and Wales by Francis Grose, 1809


Catapults (also known as onagers) were generally built around a flat rectangular frame close to the ground, to which was attached a vertical frame. Where the two frames met, a bundle of twisted rope was attached, and a lever or ‘arm’ was threaded through the rope. When the arm was pulled downwards (usually through the use of a winch or windlass), the ropes twisted further and were held under tension. A missile was placed in a cupped bucket at the end of the arm and when the weapon was fired the tension was released suddenly, propelling the arm and missile upwards and forwards.


Catapults were relatively simple pieces of machinery, but they were effective at throwing large stones and could prove to be very useful in a siege. They were first developed by the Greeks and used extensively by both the Greeks and the Romans throughout antiquity. They were still also being used as medieval weapons, although, by the 9th and 10th centuries, catapults had been largely replaced by the far more powerful trebuchet. The classic catapult could not hope to breach the stone walls which were increasingly being used in northern European castles.


6. Mangonel (Traction Trebuchet): A More Effective Launcher


Also known as a traction trebuchet, the mangonel was a type of traction trebuchet that originated in China and reached Europe in the 6th century, having been carried there by the nomadic Avars. The mangonel differed from earlier siege engines in that it did not operate using torsion – instead, it used manpower to project missiles, taking advantage of the mechanical advantage of a lever.


mangonel in action madrid skylitzes
A Mangonel in action from the Madrid Skylitzes manuscript, ca. 1100-1299, via the Library of Congress, Washington D.C.


A mangonel was essentially a large vertical frame with a large lever or ‘arm’ attached at its apex. The arm would swing vertically and was powered by men pulling on ropes attached to one end. At the other end of the arm, a sling was attached into which a missile was placed – when a team of men pulled on one end of the arm it would pivot in the frame, swinging the sling and missile upwards and forwards. The sling would then release the missile at the top of its arc.


This siege engine had distinct advantages over the catapult in that it was less complex and easier to build. It was also faster to reload, so a steady rate of fire could be kept up in order to pound the curtain walls of a fortification during medieval wars. Thanks to its simplicity and effectiveness, the mangonel remained as the preeminent siege weapon in western Europe until the advent of the counterweight trebuchet.


7. Counterweight Trebuchet: Utilizing Mechanical Advantage In A Medieval Weapon 

diagram of a counterweight trebuchet
Diagram of a counterweight trebuchet by d’Eugène Viollet-le-Duc and E. Guillaumot in Dictionnaire raisonné de l’architecture française du XIe au XVe siècle, 1854–68, via Project Gutenburg


The counterweight trebuchet was very similar in design to a mangonel or traction trebuchet, except that it employed a counterweight to swing the arm of the weapon using gravity, making it far more powerful. Counterweight trebuchets were typically large, measuring from around 10-30 meters in height. They were made this tall so that the arm of the weapon could rotate through a wide arc, usually over 180 degrees.


In order to increase the mechanical advantage of the counterweight trebuchet, the side of the arm that held the projectile was typically between four and six times longer than the side that held the counterweight. The enormous functioning reconstruction trebuchet at Warwick Castle in England (the largest in the world) stands 18 meters tall and is able to throw a 36-kilogram missile up to 300 meters.


trebuchet warwick castle
The enormous reconstructed counterweight trebuchet at Warwick Castle, via Carpenter Oak


A counterweight trebuchet’s power lies in the use of gravity and counterweight to project the missile. Potential energy is stored by raising a very heavy box (typically filled with stones) attached to the shorter end of the trebuchet’s arm, usually through the use of winches or windlasses. When fired the counterweight drops and the arm rotates through its arc gathering speed rapidly – the missile is released from its sling at the top of the arc. Just as with mangonels, stones, debris, rotting carcasses, and even incendiary ammunition was fired from counterweight trebuchets during medieval wars.


These formidable siege engines were developed in the late 12th century and were used a great deal across Europe and the Middle East. It is arguably in reaction to the power of the new counterweight trebuchets that concentric castles were developed in the crusader states of the Levant. Despite their complexity and slow reload times, counterweight trebuchets were unparalleled siege weapons until the end of the medieval period when they were superseded by increasingly effective gunpower artillery.

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By Jack CrawfordBA Medieval History, MPhil Anglo-Saxon, Norse and Celtic HistoryJack is a contributing writer with a primary interest in Medieval History, in particular the early medieval period. He completed a bachelor’s degree in Medieval History at the University of St. Andrews, and a masters in Anglo-Saxon, Norse and Celtic at the University of Cambridge.