The Middle Ages: Warfare, Castles, and Siege Engines

Dr. Ben Hudson, Penn State University Dr. Scott Metzger, Penn State University

What were the Middle Ages (medieval era)?

This phrase refers to the centuries after the fall of the Roman Empire in Western Europe until the height of the Renaissance – from around the year 500 to 1500. The era of medieval castle building was from around the year 1000 to the 1400s (until the 1500s in some parts of Europe).

What was warfare like in the medieval era?

Big field battles fought between large armies were actually rare in the Middle Ages. Since rulers depended on the personal loyalty of knights and volunteer soldiers (or else had to pay large amounts of treasure for hired troops), they tended not to want to risk them in a field battle unless absolutely necessary. Even just one serious defeat could be a political disaster for a ruler. Sieges (attacking enemy castles) were a much more frequent kind of warfare in the Middle Ages. Medieval warfare also commonly consisted of raids (quick surprise attacks mainly meant to inflict property damage) or skirmishes (short fights between fast-moving groups of soldiers).

Armor was extremely important in medieval warfare because it could protect the human body from being cut by blades or pierced by spears or arrows. Many foot soldiers wore armor made out of quilted layers of felt or linen or leather boiled and dried until it became hard. Wealthier soldiers, including most knights, wore full-body suits made out of layers of linked metal rings (“mail”) on top of a quilted jacket. For most of the medieval era, mail armor provided excellent protection against most weapons. By the 1300s the wealthiest warriors started wearing steel plates with flexible mail at the joints, and by the 1400s this evolved into full-body plate armor (the inspiration for our “knight in shining armor” fables).

Knights were the most powerful soldiers on medieval battlefields and had the highest status, but they were only a minority of soldiers in most large armies. The majority tended to be foot soldiers recruited from towns or landowning families in farming villages. Troops fighting on foot (infantry) typically were equipped with pole weapons (like spears) and shields. Other troops were archers armed with bows or crossbows. By the 1300s, the best “war-bows” (called “longbows” today) became so well engineered and powerful that they could pose a serious danger even to knights and warhorses covered in heavy armor. Armored knights were not the only horse soldiers (cavalry) on medieval battlefields. Some armies included lightly armored riders armed with throwing spears or small bows (the Mongols and Turks of Central Asia were greatly feared as deadly horse-archers).

Why were medieval castles built?

After the fall of the Roman Empire in Western Europe, there was no centralized government anymore. There were lots of kings ruling over small regions who battled each other for control over territory. These kings came to rely on knights, a social class of men who trained their whole lives to fight in heavy armor and usually on horseback. Kings rewarded their military commanders by giving them a portion of territory to rule as a lord (along with a noble title like “count” or “duke”). In return, these lords would use the resources of their territory to support a number of knights and other soldiers. In times of war, kings would call on their lords and knights for military service. Historians use the term feudalism to identify this political arrangement of granting a portion of land (called a “fief”) in return for an oath of loyalty (called “fealty”) and military service (with the actual details differing a lot from place to place).

Castles were fortified households for kings, noble lords, and knights of medieval Europe. Castles were homes where their families could live safely in case rivals or enemies attacked. They also were military bases from which knights could ride out on warhorses and enforce control over nearby towns and farming villages. In the early Middle Ages, castles were often quite small and made mostly of wood. By around the year 1100, castles were built bigger, made out of stone, and surrounded by huge stone walls. Massive stone castles were very expensive to build, and only powerful kings or rich nobles could afford them.

Why and how were castles attacked?

Castles came under attack by rival lords in a dispute, usually over claims to land or titles. If the castle could be captured, the lord’s family could be taken hostage and set free only after the lord agreed to pay land or wealth. Castles also might be attacked by invaders from an enemy region. An invading army usually could not risk ignoring a castle because it housed knights on warhorses that could ride out to attack the invaders from behind with surprise or raid the army’s supplies and then quickly retreat back into the safety of the castle.

Attacking a castle required a siege – surrounding it with an army so that nobody inside could get out and nothing outside could get in. The attacking (“besieging”) army would wait for as long as possible to wear down the food, water, and health of defenders inside the castle, but some castles had stores of food and fresh water allowing them to hold out for months or even years. If an invading army could not wait for the defenders to surrender due to starvation or sickness, soldiers would have to “storm” the castle – breaking down gates with battering rams or climbing over the walls with heavy siege ladders or siege towers on wheels.

Attackers also built machines called siege engines to wear down (“reduce”) a castle by shooting heavy objects to damage walls and towers or knock down defending soldiers. Sometimes these machines would hurl rotting, dead carcasses over a castle’s walls because it was believed this would cause disease among the defenders. What were different types of siege engines?

Siege engines date back to the ancient Greeks and Romans. The earliest versions (called a ballista) looked like big crossbows and shot big spears or stone balls by using the principle of tension. Medieval armies continued to use this kind of machine because it was easier to move and aim and fairly accurate over short distances (since it shot in a straight line).

Machines that we would recognize as catapults (the Romans called it an “onager” – their word for a kicking donkey) shot heavier stones by using the principle of torsion. Medieval armies continued to use this kind of machine because it was movable and could shoot heavier stones (for more damage) over fairly long distances, even though it was more difficult to aim.

By the 1100s-1200s, engineers were making huge machines (called a mangonel) that hurled massive stones long distances by using the principle of counterweight. The biggest counterweight machines (called a trebuchet) needed animals or people to walk on a huge wheel to raise the weight in order to reload the weapon. These machines could knock down stone walls or buildings given enough time but were difficult to move and aim.

How were castles defended?

Curtain walls made of thick stone surrounded major castles. Long stretches of wall were structurally supported by high towers made of stone. Soldiers with bows or crossbows defended the tops of the walls, and towers also had many small arrow slits through which soldiers could shoot at approaching enemies. Barbicans (stone buildings with gates and drawbridges) controlled entry through walls.

After attackers got past the walls, inside would be at least one keep (a large stone tower often square in shape and protected by strong, reinforced doors). The biggest castles had multiple keeps. The inside of a keep had many narrow hallways and staircases where attackers could be held off by small groups of defenders. Above these chokepoints were murder holes – gaps in the ceiling through which weapons, fire, or boiling fluids could be dropped on attackers. Major castles were so defensible that a small force of defenders could beat back an attacking force more than ten-times larger. (For example, in 1522 just over 7,000 defenders in a fortress on the island of Rhodes fought off a Turkish army of nearly 100,000!)

Were siege engines really the best way to take a castle?

As scary as siege engines look, most did a better job knocking defenders off of walls than breaking down stone defenses. Every hit to a stone structure would cause just a little damage. Only the biggest counterweight engines had a decent chance of collapsing heavy stonework, and even they required many direct hits (and this had to happen faster than defenders inside could repair the damage). The most reliable way to take a castle was to wait for the defenders to surrender due to sickness or starvation – but this required the attacking army to have enough supplies to wait many months (sometimes over a year). Often an attacking army would need to give up because it ran low on food supplies or because illnesses spread among the soldiers.

If an attacking army needed to risk storming a castle to take it more quickly, the best way to collapse stone defenses was to undermine (or “sap”) them – having soldiers (called sappers) dig tunnels underneath the heaviest portions of walls, towers, or keeps. With gravity pulling the structure downward into the empty tunnel, the stonework would collapse under its own weight and expose a gap through which attacking troops could charge. However, the castle’s defenders could attempt to countermine – digging tunnels to block the attacking army’s tunnels before they reached the defenses. When defenders were able to tunnel over the attackers’ tunnels, they poured down fire, smoke, and other deadly substances to kill the enemy diggers.

Why did the era of castles end?

By the 1400s-1500s, gunpowder weapons spread around Europe. Cannon fired stone or metal balls with far more power than catapults and could more quickly reduce stone walls. It was no longer cost-effective for most landowners to build their own castles. Gunpowder handguns (muskets) quickly became too powerful to be blocked by armor, which meant that armored knights lost their advantage on the battlefield. Foot soldiers with spears and handguns became more important. Without a military need for large numbers of knights spread all over a kingdom, castles no longer had a military role by the 1500s. Instead, towns and cities (where foot soldiers were recruited) became more important and were protected by vast rings of stone walls and forts (to house defensive cannon and troops).

What happened to knights after the medieval era?

Though the “feudal knight” disappeared by the end of the Middle Ages, the social class they came from did not. Descendants of medieval knights and lords became the “gentry” and “aristocracy” (wealthy landowning families) of Europe during the 1500s-early 1900s. Armies during these later centuries still had soldiers who fought on horseback, even though cavalry was not as important as in the Middle Ages. Many horse soldiers during these centuries still came from the families of the gentry and aristocracy, whose ancestors fought as knights.

Graphics Source: The Harper Encyclopedia of Military History by R. Dupuy and T. Dupuy