Sieges. (pt 1, 2 & 3)

[Longmane]

I thought I'd use the opportunity of work being far less hectic then usual to begin posting a few pieces from another new tomb I've just got,
(Johnston, Ruth A, -All Things Medieval~An Encyclopedia of the Medieval World-) as while of course impossible go into as much detail as books which deal specifically with each of the topics, it nevertheless not only gives a remarkably interesting, accurate description/explanation of each one, but also in a very concise way considering.

Sieges. (pt1)

In ancient times, cities often had strong walls around them, and warfare against these cities had always involved the basic tasks of breaking the walls, going over or under the walls, or starving the defenders into surrender.

In the Middle Ages, Europe's decentralized political structure put a new twist on the siege by planting heavily fortified castles all over the landscape. Constantinople's thick city walls were similar to the fortresses of Roman, Greek, and more ancient times.  Northern Europe, on the other hand, had several hundred small fortresses that were designed to hold off disproportionately larger attackers.  In order to capture a region, an invader would need to besiege more than one fortress.

After the period of the First Crusade, knights returned with much grander ideas of defensive fortification. They had seen Byzantine fortress designs and had participated in attacks on Antioch, Acre, Jerusalem, and Tyre.  Crusaders had built their own fortresses to hold the new territory, and they had used local engineering and labor to build much larger stone fortresses than Europe had at the time.  When they came home, many rebuilt their family castles to incorporate the new defensive features.  Castles became harder to capture by direct assault.

Sieges, attacks that stretched out over a long period of time, were the only way of capturing a castle unless it was taken by surprise.  Sieges were expensive for both sides. The attackers had to sustain an army in hostile territory for a number of months, while the defenders had to make their food and water last.  Both sides worked hard to attack or defend the walls.  Walls could be broken down or surmounted by going over or under the walls.  Siege machinery falls into three basic types.  Catapults threw projectiles over the castle walls, either into the castle or from the castle toward the attackers.  Rams battered the walls to make them fall down.  Siege towers lifted attackers to the top of the wall so that they could enter.

Because of the high stakes and expense, sieges were not governed by the polite rules of chivalry.  No trick was too dirty, gross, or savage.  Treachery was one of the best ways of breaking a siege, if an insider could be bribed to open the gates or tell of a secret weak point.  Poison or bacterial contamination of food or water was a popular way to break a siege.

Climbing, Ramming, and Digging

The simplest siege weapon was the ladder.  The attackers wanted to get into the fortress, and one way was to go over the walls. Siege ladders had been used against city and fortress walls since ancient times. Basic facts that governed the construction of siege ladders began with length: if a ladder was too short, it would not allow the attacker to go over the top, but if it was too long, its top would stick up where defenders could shove it away. The ladder had to lean enough to be stable, but it had to be vertical enough to be strong.  The ideal siege ladder came to just below the top of the wall, and its foot was placed at a distance from the wall equal to about half its length.  Since the walls of a town or castle were of varying heights, and were surrounded by varying terrain, the attackers had to build custom siege ladders for each position.

A refinement on the simple ladder was a ladder with a bridge. The bridge was a sturdy plank hinged at the top of the ladder, raised by ropes.  The ladder had to be somewhat freestanding, like a platform, since it could not lean against the wall.  Some engineers designed folding ladders that could be made in advance and carried with the army or ladders that could be assembled from short sections.  Some sieges also used ladders made of rope or leather, with hooks at the top.  These ladders were for quiet night attacks, when the ladders could suddenly appear hooked on top of the walls by long poles without the defenders having seen any ladders.

Defenders tried to repel attackers on ladders by using the force of gravity.  Standing at a higher level, they could drop harmful substances on the climbers.  Most often, they threw large rocks to knock the attackers off the ladders or force them to cover their heads.  Sometimes they threw or poured boiling water, oil, or any other hot substances they had on hand, such as tar.  They could also throw quicklime, a highly caustic, alkaline material that burned on contact.  In sandy places, they could heat sand to red-hot and fling it down. In some cases, they could fling nets onto the attackers when they reached the top and trap them.

To protect against all these defences, attackers used heavy shields.  Since classical times there had been siege shields made, tall, curved back, or with a small roof, and at times on wheels.  Many shields were large enough for more than one man.  Medieval sieges used all forms of wooden shields, covered with leather.  In the 15th century, the tall siege shield was called a pavis.  It often had a spike to drive into the ground and a pole to hold it up.

Of course, the first defence against siege ladders had been put in place before the siege began, when the fortress was designed.  Most fortresses used a ditch or moat that came as close as possible to the outer walls. Attackers had to fill in the ditch with sacks or barrels of rocks and earth.  In some cases, they resorted to using catapults to land rocks and dirt in the moat.  Unless the ground was reasonably level approaching the wall, their use of siege machines would be limited.

If the attackers continued to try to go over the walls, but needed more than ladders, the next logical step was to make portable sheds.  Sheds could be made fire resistant with water and fresh skins.  Sheds could also disguise or protect structural attacks, such as digging or battering rams.  The purpose of a ram is simple.  It is a strong tree trunk that hits a wall, gate, or door repeatedly until the object is smashed. 


The next 2 parts will be dealing with the Battering ram in proper detail, as likewise siege towers and undermining.

[Zakilevo]

Very interesting. Thank you :) Never knew the crusade influenced the castles.

[Longmane]

pt2/


The purpose of a ram is simple. It is a strong tree trunk that hits a wall, gate, or door repeatedly until the object is smashed.  The design of a battering ram had three aims: to strengthen the ram itself, to increase its force, and to protect its operators from counter-attack.

The end of the battering ram was strengthened by a metal tip.  Sometimes this was actually in the shape of a ram's head, invoking the ram's butting strength and using the ram's extended snout as the focal point of the battering force.  More often, it was a blacksmith's iron binding so that the wood did not shatter as easily from the force put on it.  The ram's bulk was suspended by ropes that could swing it, so the operators of a battering ram did not need much human power to strike with it.  Longer ropes, of course, gave it more swinging power.  The frame that suspended the ram was usually roofed so that its operators were protected from arrows or stones.  Finally, the roof was often covered with damp animal skins as fire prevention.

Defenders dropped projectiles and hot liquids on the operators of battering rams.  They could also try to disrupt the action of the ram, if the ram's housing was too well defended to be vulnerable to rocks or fire. When the ram struck the wall, they could try to hook it and pull it up, either deflecting its blow or flipping its shed over. 

Battering ram technology had been well explored during classical times, and, although rams were still used, castle designers built walls to withstand them.  The thickest parts of the walls were at battering level, and gates, the main target of rams, were protected by gatehouses and moats.  Attackers had to find new ways to use rams during the Middle Ages.  Small rams could be mounted on ladders and lifted up to smash parapets.  Attackers could build an earth ramp to a higher point in a wall, where it was likely to be thinner.

Attackers could also try to drill holes in the walls. Borers, too, had to work in the shelter of sheds and shields.  It was not easy to drill holes in stone walls, so borers were more commonly used against brick. They were not a large feature of Northern European siege warfare, since most French and English castles were made of limestone and granite.  A strong brick wall could be sufficiently weakened by holes that a ram could bring it down. Holes could have wood pushed in and set on fire, and the heat further weakened the walls.

By the 14th century, castle walls were built to be too high and thick for ladders and rams to be effective.  If ladders and rams could not boost attackers over or batter walls down, a more elaborate machine could be built.

A siege tower was a heavy, cumbersome machine, not designed for a lightning attack or for secrecy.  It was part of an all-out assault on a weakened castle.

The tower was a tall wooden structure on wheels; it was sometimes called a castle or a cat.  It had protective walls and a roof and was fireproofed if possible.  Inside, it had wooden floors as stories where attackers could stand.  A ladder led from bottom to top, so each layer of attackers could climb the ladder in turn.  A top floor allowed archers to give further defensive cover to the attackers.  The siege tower also had a bridge to cross to the top of the wall. This bridge could be a drawbridge, operated by a windlass in the bottom story.

Certain engineering issues governed the construction of siege towers. They had to be tall enough to reach the walls and stable enough not to tip when loaded with climbing soldiers.  They also had to be portable, usually on wheels.  Medieval siege towers were as tall as 75 feet high, but they were often shorter.  Designs in medieval illustrations appear to favor a small fortress on a rolling platform, reached by one or more ladders. The attackers expected a tough fight before they could cross a bridge, and they designed it to have walls or even a roof.

Other siege towers were more like rolling platform ladders with bridges.  The builders had to think about fire, since the most common way to defend against a siege tower was to set it on fire.  In the Byzantine region, siege towers became obsolete when it became clear the defenders would hurl Greek fire at them.  Northern Europe was able to use siege tower tactics longer, since it was easier to defend wood against ordinary fire. The tower could be roofed with fresh turf or newly skinned wet hides.

Siege towers were heavy and could easily tip over. It was difficult to move them into position from the safe distance where they had been built. The ground had to be level, and many teams of oxen were needed to move them.  They also needed to be moved close to the walls, which normally meant that pushing, not pulling, force was required.  One way to move a very heavy siege platform was to sink one or more posts into the ground by the castle walls and loop heavy pulleys and ropes around them.  The platform was then attached to the ropes, and it could be moved forward by oxen walking away from the battle.  The siege tower inched closer to the fortress walls, but the muscle power moving it only moved farther out of range.  The tower could come right up to the pulleys, if the defenders had not disrupted them. Towers could also be moved with levers, but, in any case, they moved very slowly because of their great weight.

[Longmane]

pt3/

Undermining a wall could be the most successful attack, and there were fewer ways for the defenders to work against it.  Ideally, the defenders would not know that sappers were digging a tunnel under the walls. The first somewhat successful underground attack in medieval times was carried out by the Vikings when they besieged Paris in 885.  After the Norman conquest of England, mining was part of many sieges.  The siege of Rochester Castle in 1215, when King John of England was putting down a rebellion, was one of the few times when mining was a key factor in the castle's surrender.  Miners dug under two outer walls so that the defenders were trapped in the keep.  Château-Gaillard, built by King Richard I of England, was designed to be impregnable, but miners collapsed its walls twice.  Mining was a large part of Crusader warfare, on both sides.

The best location to begin a sapping operation was in a place where the defenders could not observe what was going on without leaving the fortress.  Sappers sometimes needed to start some distance away, on the other side of a hill.  The attackers could put up a wooden palisade so that the defenders could not see what they were doing on the other side.  If the diggers had to start in a place where the defenders could observe them, they needed a strong shed to protect them.  The shed was sometimes nicknamed a "tortoise" or a "sow."

An attacking army drafted industrial miners to dig their siege tunnels.  Since stone was tunneler from deep underground, even from under the city of Paris, miners knew how to dig any length of tunnel required, through any materials.  Beginning in a safe place, they dug underground and moved in a carefully planned direction toward the walls.  Sometimes, two tunnels were dug as parallel galleries.  As the miners tunneled, they shored up the walls of the mine with strong timbers.  Mining was an operation that required a large number of laborers, which made it difficult to carry out deep in hostile territory.

When a tunnel successfully reached a point under the defensive wall, the miners nearly always started a fire. The intense heat caused the ground to expand, which cracked the walls and collapsed the tunnel.  Added to the wood carried into the tunnel, oil and fat made the fire burn hotter; one mine fire, in the siege of Rochester, used 40 pigs as sources of fat. The wood props securing the tunnels also burned, allowing the tunnels to collapse faster.

Once gunpowder was in use, it was even easier to produce a hot blast. It was harder to get away safely, since the combustion happened so quickly and the blast collapsed the tunnel.  The best way was to approach the wall with snake-like curves and then use the curved passages to set a long fuse, out of sight and reach of the blast.  As the fire crept along the fuse, the miners could escape out the end of the tunnel.  Since gunpowder came into use at the end of the Middle Ages, it did not become a major force in siege mining until the Renaissance period.

Most walls collapsed when the ground supporting them caved in. There were few ways to build walls that were not vulnerable to sapping.  One way was to reinforce the walls with stone columns laid like pegs through holes in the building stones.  Places with ruined Roman or Greek columns could use them this way, but most places did not have ruined columns.  The fortress design could also use very deep digging to place a moat or a wall in vulnerable places.

Defenders tried to detect tunnel digging when they could not see it.  A bowl of water, set over an area being mined, quivered with the vibrations of the tools.  If they could tell where the miners were approaching the wall, the defenders could dig down to meet and surprise them with combat. They could sink a hole nearby and try to set the attacking tunnel on fire, or they could flood it if they had a moat or river inside the walls. The attackers tried to make their tunneling less predictable by making decoy tunnels or by making the tunnels take unexpected paths.  Tunnels could branch out, or they could zigzag or curve.


NB I'll be posting something about ballistic machines later,  (catapults, trebuchets ect) being as of course some of them were often used in sieges.