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In the Medieval period besieging armies used a wide variety of siege engines including: scaling ladders; battering rams; siege towers and various types of catapults such as the mangonel, onager, ballista, and trebuchet. Siege techniques also included mining.

Advances in the prosecution of sieges encouraged the development of a variety of defensive counter-measures. In particular, medieval fortifications became progressively stronger — for example, the advent of the concentric castle from the period of the Crusades — and more dangerous to attackers as witnessed by the increasing use of machicolations and murder-holes, as well the preparation of hot or incendiary substances. Arrow slits, concealed doors for sallies, and deep water wells were also integral to resisting siege.

Designers of castles paid particular attention to defending entrances, protecting gates with drawbridges, portcullises and barbicans. Wet skins of freshly slaughtered animals were draped over gates, hourdes and other wooden structures to retard fire. Moats and other water defences, whether natural or augmented, were also vital to defenders.

In the European Middle Ages, virtually all large cities had city walls. Carcassonne and Dubrovnik in Dalmatia are well-preserved examples. The more important cities had citadels, forts or castles inside them, often built against the city walls. Great effort was expended to ensure a good water supply inside the city in case of siege. In some cases, long tunnels were constructed to carry water into the city. Complex systems of underground tunnels were used for storage and communications in medieval cities like Tábor in Bohemia.

Attackers would try to get over the walls using scaling ladders, siege towers called belfries, and grapples. Alternatively they could try to get through the doors using a battering ram, or through the walls using heavy artillery. They might try tunnelling under the walls to gain access, but more often they would try to undermine the walls to bring them down.

In a siege one army typically attacks an enemy within a stronghold. either a castle or a fortified town. Medieval towns were generally surrounded by defensive walls, just like castles. Indeed the distinction between castles and fortified towns is often blurred. Castles were often located within fortified towns - in fact many towns grew up around existing castles - so that the castle became a sort of citadel within the fortified town.

Attackers therefore often had two sets of obstacles - first the city walls, then the castle walls. This could lead to interesting complications as at Beaucaire in 1216. For months Simon de Montfort besieged Raymondet in the town, while Raymondet besieged a garrison loyal to de Montfort in the castle within the town.

Sometimes there were three sets of obstacles, because fauxburgs with their own defensive walls were often built on to the exterior of city walls, as at Carcassonne and Termes.

Besiegers had a number of techniques for gaining control of their objective - either by forcing a way in, or by forcing the besieged garrison out. Specific techniques - established since prehistoric times - include:

  1. Breaching the walls or doorways. Attackers would use weapons to get through walls. Examples are stone throwing machines

petriers such as trebuchets and mangonels); machines to knock holes in walls such as battering rams; and engines to extract individual dressed stones one by one (cats, weasels and simple picks).

  1. Tunelling under the walls. Attackers would build mines, either to gain access to the interior or to undermine and collapse

the defensive walls.

  1. Getting over the walls. Attackers would use scaling ladders and siege engines such as large mobile wooden towers known as


  1. Sitting and waiting. If communications between the besieged and the outside world could be cut then the defenders could be

denied food supplies and sometimes water (as at Beaucaire, Carcassonne, Minerve, and Termes). This was not always possible (as for Raymondet at Beaucaire and at Montsegur). The word siege means "to sit", an indication that this was a standard technique.

  1. A Fifth Column. Inducing someone on the inside to assist the attackers, either by bribery or exploiting divided loyalties.

They could for example open a postern gate at night. Occasionally attackers could be smuggled in to the besieged fortification to fulfil this role, as for example in ancient times in the famous Trojan horse.

  1. Diplomacy, threats, terror and psychological techniques. To help weaken the will of the defenders, attackers could make threats or promises, or terrorise the defenders - for example

by mutilating or executing hostages, or by using throwing machines to lob fire, or human heads or other body parts, into the the fortification.

  1. Biological Warfare. Medieval besiegers were known to project diseased animals into fortifications with the deliberate

intention of spreading disease and so weakening the garisson. I some cases it was possible to poison water supplies, though most fortifications had their own wells or water cisterns. Until the invention of gunpowder-based weapons (and the resulting higher-velocity projectiles), the balance of power and logistics definitely favoured the defender. With the invention of gunpowder, the traditional methods of defence became less and less effective against a determined siege, giving rise to a new form of defensive structure, the star-fort.

Siege Towers Edit

The medieval belfry was not a church tower, but a siege engine - the modern meaning seemsto have come about by the erroneous association of towers and bells (etymologically, the bel in belfry is not connected with the word "bell").

A belfry was used for gaining access to a castle, generally at the level of the battlements. It was typically constructed in wood, on several stories - as many as necessary to reach the battlements. Each story offered a location for attack - bows and crossbows in the lower levels, and armed men in the upper level, ready to drop a sort of drawbridge and gain access to the castle ramparts. The belfry was normally wheeled, so that it could be moved up against the castle walls, and like all exposed wooden engines of war it would be covered in the hides of freshly slaughtered animals and regularly dowsed in water to keep it fireproof.

One way to foil the approach of a belfry was to have sloping castle walls. This forced the attackers to cover a greater distance from the top of the belfry to the top of the castle wall. This was one of the benefits of a talus.

Another way to foil the approach was to build ditches and moats to prevent the approach of belfries.

As on the right, attackers often needed to fill up the ditch or moat to provide a level surface that extended all the way to the foot of the castle wall.

In practice, all sorts of material was used for this: earth, rocks, straw, dead bodies, wood, whatever came to hand. If too much wood was used in the infill then the infill itself became a target for fire setters.

Battering Rams Edit

A battering ram is a siege engine originating in ancient times to breach fortification walls or doors. In its simplest form, a battering ram is just a large, heavy log carried by several people and propelled with force against the target, the momentum of the ram damaging the target.

Some battering rams were supported by rollers. This gave the ram much greater travel so that it could achieve a greater speed before striking its target and was therefore more destructive. Such a ram was used by Alexander the Great

In a more sophisticated design, the ram was slung from a wheeled support frame so that it could be much more massive and also more easily swung against its target. Sometimes the ram's attacking point would be reinforced with a metal head. A capped ram is a battering ram that has an accessory at the head (usually made of iron or steel, traditionally shaped into the head and horns of a ram to do more damage to a building.

Many battering rams had protective roofs and side-screens covered in materials, often fresh wet hides to prevent the ram being set on fire, as well as to protect the ram's operators of the ram from enemies firing arrows down on them.

An image of an Assyrian battering ram shows how sophisticated attack and defence had come by the 9th century BC. In the image defenders are trying to set the ram alight with torches and have also put a chain under the ram. The attackers are trying to pull on the chain to free the ram - the same scene could have been depicted in Roman, Visigothic or Medieval times.

When a castle was being attacked, defenders attempted to foil battering rams by dropping obstacles in front of the ram just before it hit a wall, using grappling hooks to immobilize the log, setting the ram on fire, or sallying out to attack the ram. Battering rams had an important effect on the evolution of defensive walls - the talus for example was one way of reinforcing walls. In practice, wooden gates would generally offer the easiest targets.

Raymondet, the future Raymond VII, Count of Toulouse, used a ram at Beaucaire in 1216. He was himself besieged in the town by Simon de Montfort's Crusader forces, while he himself was besieging the garisson of the castle within the fortified town. The The Song of the Crusade (the Canso) tells us a little about the ram. We know for example that it had an iron head. The poet tells us that it was:

"... long, straight, sharp and shod with iron; it thrust, carved and smashed till the wall was breached and many of the dressed stones thrown down. When the besieged Crusaders saw that, they did not panic but made a rope lasso and used a device to fling it so that they caught and held the ram's head, to the rage of all in Beaucaire.

Then the engineer who had set up the battering ram arrived. He and his men slipped secretly into the rock itself [presumably the hole already made by the ram, intending to break through the wall with their sharp picks. But when the men in the keep realised this, they cast down fire, sulphur and tow together in a piece of cloth and let it down on a chain.

When the fire caught and the sulphur ran, the flames and stench so stupefied them that not one of them could stay there. Then they used their stone throwers and broke down the beams and palisades." (The Song of the Crusade, laisse 164).

The Cat Edit

A Cat was a wooden structure built (or moved) up to a defensive wall. From surviving documents it seems that an arm could manipulated to claw away at the castle wall - hence the name.

Cats could be large multi-purpose structures, perhaps with a trebuchet on top and sappers operating from the protected interior.

Cats were much feared and if they possibly could, castle defenders would try to destroy them by mounting sorties, by using stone throwing engines, or by setting fire to them.

Like all wooden siege engines they would be routinely covered in the skins of freshly slaughtered animals and regularly dowsed with water to keep them fireproof.

Simon de Montfort used a cat at the Siege of Beaucaire in 1216, but unsuccessfully. According to the Canso it had "no more effect than an enchanter's dream". It was "a spider's web and a sheer waste of material".

Perhaps the most famous cat was one Simon built two years later, attempting to besiege the City of Toulouse in 1217-18. It was while protecting his cat from counter attack by the citizens of Toulouse that Simon de Montfort was struck on the head by a massive stone projectile from a trebuchet on the city walls, and killed instantly.

The Weasel Edit

A weasel was a similar sort of structure to a cat, but smaller and lighter. It seems to have been more manoeuvrable and used a spike rather than a paw to attack castle walls.

It may have taken its name from its business end looking like a weasel's nose, or perhaps its long thin body, or both.

A weasel was used by the forces of Raymondet, the future Count Raymond VII of Toulouse, at Beaucaire in 1216 according to the The Song of the Crusade (Canso de la crozada). As Simon de Montfort was conducting a Council of War, a beggar burst in, shouting that he had seen a weasel. The weasel was already against the citadel wall and ready to drive a spike into it. The defenders were quick to react. The chief engineer hurled a pot of molten pitch at it, hitting it in exactly the right spot and it burst into flames.

Chemical Warfare - Greek Fire Edit

Incendiary devices were standard weapons of war. Wooden defences always needed protection from burning. Wet animal hides were highly effective against burning arrows so military engineers dedicated themselves to finding ways of ensuring that fires burned as long and as strongly as necessary to catch. All sorts of chemicals could be used for this purpose - petroleum, sulphur, quicklime and tar barrels for example.

Liquid fire is represented on Assyrian bas-reliefs. At the siege of Plataea in 429 BC the Spartans attempted to burn the town by piling up against the walls wood saturated with pitch and sulphur and setting it on fire, and at the siege of Delium in 424 BC a cauldron containing pitch, sulphur and burning charcoal was placed against the walls. A century later Aeneas Tacticus mentions a mixture of sulphur, pitch, charcoal, incense and tow packed in wooden vessels, ignited and thrown onto the decks of enemy ships. Formulae given by Vegetius around AD 350 add naphtha or petroleum. Some nine centuries later the same substances are found and later recipes include saltpetre and turpentine make their appearance. The ultimate in this form of chemical warfare was called Greek-Fire.

Greek fire was a burning-liquid used as a weapon of war by the Byzantines, and also by Arabs, Chinese, and Mongols. Incendiary weapons had been in use for centuries: petroleum and sulphur had both been in use since the early days of the Christianity. Greek fire was vastly more potent. Similar to modern napalm, it would adhere to surfaces, ignite upon contact, and could not be extinguished by water alone.

Byzantines used it in naval battles to great effect because it burned on water. It was responsible for numerous Byzantine military victories on land as well as at sea - and also for enemies preferring discretion to valour so that many battles never took place at all. It was the ultimate deterrent of the time, and helps explain the Byzantine Empire's survival until 1453. There was no defence. As the Lord of Joinville noted in the thirteenth century "Every time they hurl the fire at us, we go down on our elbows and knees, and beseech Our Lord to save us from this danger." Men were known to simply flee their posts rather than face Greek Fire. On the other hand Greek fire was very hard to control, and it would often accidentally set Byzantine ships ablaze.

Greek Fire is said to have been invented by a Syrian Engineer, one Callinicus or Kallinikos, a refugee from Maalbek, or an architect from Heliopolis in the Byzantine Province of Judaea, in the seventh century (673 AD). The formula for Greek fire was a closely guarded secret and it remains a mystery to this day.

The term Greek Fire was not attributed to it until the time of the European Crusades. Some of the original names include Liquid Fire, Marine Fire, Artificial Fire and Roman Fire. (Muslims against whom the weapon was used called the Byzantines Romans).

The weapon was first used by the Byzantine navy, and the most common method of deployment was to squirt it through a large bronze tube onto enemy ships. Usually the mixture would be stored in heated, pressurised barrels and projected through the tube by some sort of pump, operators being protected behind large iron shields. Byzantines used Greek Fire only rarely, apparently out of fear that the secret mixture might fall into enemy hands. The loss of the secret would be a greater loss to Byzantium then the loss of any single battle.

In 678 the Byzantines utterly destroyed a Muslim fleet - over 30,000 men were lost. In 717-718 Caliph Suleiman attacked Constantinople (Byzantium). Most of the Muslim fleet was once again destroyed by Greek Fire, and the Caliph was forced to flee. There is virtually no documentation of its usage after this time by the Byzantines and it is generally believed that it was during this era that the secret of creating Greek Fire was lost. Formulae used after this date never seems to have had the same devastating effect.

Some form of Greek Fire continued to be used for centuries. Byzantines used it against the Venetians during the Fourth Crusade. A so-called "carcass composition" containing sulphur, tallow, rosin, turpentine, saltpetre and antimony, became known to the Crusaders as Greek fire but is more correctly called wildfire.

So far, no-one has been able to recreate Greek Fire. Arabian armies, who eventually created their own version sometime between the mid-seventh century and the early tenth. It was relatively weak copy of the original Byzantine substance, though still one of the most devastating weapons of the period. Arabs used the Greek Fire much like Byzantines, using brass tubes mounted aboard ships or on castle walls. They also filled jars with it, to be hurled by hand at their opponents. Arrows and javelins would be used to carry the mixture further and engines of war could be used to throw larger amounts over castle walls.

As a defence, water alone was ineffective. On land sand could be used to stop the burning . Intriguingly it is also known that vinegar and urine were effective - suggesting an alkaline composition that could be neutralised by acid. According to some accounts pure or salt water served to intensify the burning, suggesting that Greek Fire may have been a 'thermite-like' reaction, perhaps involving quicklime. According to some sources, Greek Fire burst into flames on contact with water. Some have suggested phosphorus, Others have suggested a form of naphtha or another low-density liquid hydrocarbon (petroleum was already known in the East). There are numerous candidates including liquid petroleum, naphtha, burning pitch, sulphur, resin, quicklime and bitumen, along with a hypothetical unknown "secret ingredient". The exact composition is unlikely ever to be deduced from the inadequate surviving records.

It is not clear from contemporary reports if the operator ignited the mixture with a flame as it emerged from the syringe, or if it ignited spontaneously on contact with water or air. If the latter is the case, it is possible that the active ingredient was calcium phosphide, made by heating lime, bones, and charcoal. On contact with water, calcium phosphide releases phosphine, which ignites spontaneously. The reaction of quicklime with water also creates enough heat to ignite hydrocarbons, especially if an oxidiser such as saltpetre is present.

Ingredients were apparently preheated in a cauldron, and then pumped through a pump or used in hand grenades. If a pyrophoric reaction was involved, perhaps these grenades contained chambers for the fluids, which mixed and ignited when the vessel broke on impact with the target.

Biological Weapons == Medieval warriors also used basic biological weapons, for example catapulting dead and diseased animals into a defended fortress to help spread disease.

Psychological Weapons Edit

Ancient armies had used sophisticated psychological weapons. For example would have mad armour suitable for a man of several times normal size. He would then leave a few samples laying around the scene of his victories against the Persians. After he had gone Persians would find this armour and were were soon spreading stories of Alexander's superhuman giant soldiers. Christendom did not stretch to this level of sophistication, but it did engage in some psychological warfare, spreading rumours for example, sometimes with success effectively turning a military defeat into a political victory. Other examples of psychological warfare include making loud noises (an old Celtic practice) and catapulting the severed heads of captured enemies back into the enemy camp.

Defenders in castles under siege might prop up dummies beside the walls to make it look like there were more defenders than there really were. They might throw food from the walls to show besiegers that provisions were plentiful (Dame Carcas, who saw off the Franks, supposedly gave her name to Carcassonne after feeding the last few scraps of food in the besieged city to the last pig and then tossing over the walls as a present to the Franks. As intended, they deduced that their siege was useless and raised it the next day).

Firearms provided a strong psychological benefit when they were introduced, even though their rate of fire rendered them almost useless - and their users often blew themselves up rather than the enemy - literally hoist by their own petard.

Mining, Undermining Defensive Walls Edit

A"mine" was a tunnel dug to destabilise and bring down castles and other fortifications. The technique could be used only when the fortification was not built on solid rock. It was developed as a response to stone built castles that could not be burned like earlier-style wooden forts.

A tunnel would be excavated under the outer defences either to provide access into the fortification or more often to collapse the walls. These tunnels were supported by temporary wooden props as the digging progressed, just as in any mine. Once the excavation was complete, the mine was filled with combustible material. When lit it would burn away the props leaving the structure above unsupported and liable to collapse.

To save effort attackers would start the digging as near as possible to the wall or tower to be undermined. This exposed the sappers to enemy fire so it was necessary to provide some sort of defence. Pierre des Vaux de Cernay recounts that at the siege of Carcassonne in 1209, during the Cathar wars (Albigensian Crusade),

"... after the top of the wall had been somewhat weakened by bombardment from petraries, our engineers succeeded with great difficulty in bringing a four-wheeled wagon, covered in oxhides, close to the wall, from which they set to work to sap the wall" (Historia Albigensis - Pierre des Vaux de Cernay, 53).

Successful sapping usually ended the battle since either the defenders would no longer be able to defend and surrender, or the attackers would simply charge in and engage the defenders in close combat.

There were several methods to resist under mining. Often the siting of a castle would be such as to make mining difficult. The walls of a castle could be constructed either on solid rock or water-logged land making it difficult to dig mines. A very deep ditch or moat could be constructed in front of the walls, or even an artificial. This makes it more difficult to dig a mine and even if a breach is made the ditch or moat makes exploiting the breach difficult.

The defenders could also dig counter mines. From these they could then either dig into the attackers tunnels and sortie into them to either kill the sappers or to set fire to the pit-props to collapse the attackers' tunnel. Alternatively they could undermine the attackers' tunnel to collapse it.

If the walls were breached they could either place obstacles in the breach for example a chevaux de frise to hinder an attack, or construct a coupure.

The practice has left us reminders in English. "undermining" has acquired figurative as well as literal meanings. And military engineers are still known as Sappers.

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