This is How Medieval Sieges Worked

Sieges were a key part of medieval warfare. But while movies usually show sieges with countless siege towers, large amounts of trebuchets, and heavy fighting, not every medieval siege looked like that. (Don`t worry, the technique of besieging a castle with trebuchets, ladders, and siege towers will of course also be presented under the third headline).

In the following, I would like to explain how medieval sieges worked, why besiegers often tried to avoid taking a fortification by brute force, and what alternatives existed to actively attacking and conquering a besieges fortification.

Most medieval fortifications were rarely (if at all) besieged. But if they were the besiegers could either try to starve out the besieged by cutting them off from all supply lines or try to actively capture the castle. In that case, the attack had to be prepared by using war machines like trebuchets or techniques like undermining the walls to bring down a part of the wall since trying to overcome the walls with ladders was rarely successful. Oftentimes besieged castles surrendered after some time since that offered advantages for both sides.

Let`s find out more!

Capturing a castle by starving out the besieged

Having to perform a siege was never an ideal scenario.

Even besieging fortifications that were only defended by a small garrison made it necessary for the besieger to maintain a relatively large army. A large number of men was needed to overcome the advantage that the besieged had within their fortification when an attempt of taking the besieged fortification by force was made.

But even when the plan of the besieger was not to directly attack the besieged castle but rather starve out the besieged a large army was needed to cut off every way through which reinforcements or supplies could be brought into the besieged fortification.

To do that a large army had to be deployed for the siege. You can find out more about the size of medieval armies in my article here.

And maintaining such a large army was not only expensive, but bringing enough supplies for the besieging army could also prove difficult when the logistics did not work properly. More about how the logistics of medieval warfare worked in my article here.

But even in the case that the besieger had enough money to maintain his army for some time and the logistics were working properly a siege was still a risk. And that risk had to do with the accommodation of the besieging army.

Before a siege started the soon-to-be besieged force would burn down all houses, barns, and other accommodations close to the fortification so that the besieging army could not find proper accommodation and had to live in shacks and tents under conditions that were ideal for the spread of diseases like Dysentery.

Under these living conditions, epidemics could quickly spread which could end a siege. Additionally, an army that camped in shacks and tents could only really uphold the siege during the warmer months, as soon as winter hit these living conditions were no longer sustainable which could also quickly end a siege.

But epidemics were not limited to the besieger. The besieged who were living in cramped fortifications and with rationed food supplies were also at a risk to succumb to epidemics.

So to sum it up. If a besieger wanted to starve out the besieged by cutting off all of his supply lines he not only needed a large and expensive army but he also had to be able to maintain that army for months or even years. Additionally, that strategy only worked when the besieged could not hope for the arrival of a friendly army that would relieve them.

That last point, the hope of getting relieved by a friendly army, will also become important later when we talk about surrendering a castle as a beneficial way for both sides to end a siege.

But I think it has become clear that the active capture of a fortification without months or even years of besieging had its advantages.

Capturing a castle by actively besieging and attacking it

So we have already found out that cutting a besieged castle off from its supply lines could not only be a multi-year-long endeavor but could also be extremely expensive since the soldiers of the besieging army needed to be paid. More on the pay of medieval soldiers here.

Additionally, you always had the risk that the besieged could get help from a friendly army that would attempt to lift the siege.

So ideally you would capture the besieged castle as quickly as possible and without having to wait for months until the besieged had no more food. In that case, an attack was the way of choice to capture the besieged castle.  

If you wanted to do that then you basically had two options. Both options had their advantages and disadvantages that will be explored in the following.

Capturing a castle by surprise and without a siege

Since both a siege with the approach of starving out the besieged and a siege with the approach of capturing the besieged castle with a large attack were expensive and time-consuming ventures the best way to capture a castle was to avoid both of them.

Ideally, the besieger captured the castle in a coup. To do that a small force of men had to take the guards of the castle by surprise and capture the gatehouses so that the main army could enter the fortification.

But while that sounds good in theory it had some flaws. First of all, you had to be able to attack the defenders by surprise. And additionally, castles were built in a way to prevent these coups. To prevent surprise attacks like that castles normally had several guarded gates and gatehouses so that if one of the gatehouses was captured by surprise there were still others that prevented the attacker from entering and capturing the entire fortification.

Because of that, it was not overly common for castles to be captured in a coup and more elaborate and costly siege techniques were necessary.

Capturing a castle through an attack that is prepared by a siege

Capturing a castle by an attack that is prepared by the use of siege equipment like trebuchets is probably the way that most of us imagine a medieval siege.

But the most obvious problem with taking a besieged castle by brute force are the defenses that were put in place to prevent exactly that.

The defenses of a medieval castle and how to overcome them

A medieval castle was built to withstand attacks. Ditches, walls, and towers had the purpose of preventing the castle from being captured. A siege and elaborate equipment like siege towers and trebuchets but also techniques like undermining the walls were necessary to prepare an attack that could overcome these defenses.

Let`s now look at the different defenses and how the besiegers could overcome them.

The first obstacle that actually came before the walls of the castle was the ditch. To be able to bring equipment like ladders or even siege towers up to the wall that ditch had to be filled with stones, soil, or bundles of sticks. Sounds easy enough, doesn`t it? The problem was that the men who had to bring the stones and the other materials with which the ditch was filled were in the range of the archers on the walls of the besieged castle.

And since these men had to carry baskets full of soil or stones they could not use a shield to protect themselves from the arrows that were shot at them from the castle walls without having to sacrifice the basket size they could carry. But filling up these ditches was necessary for being able to bring ladders or even siege towers up to the walls. So the high blood toll that filling the ditches took was often accepted.

But while filling up the ditches with soil, stones of bundles of sticks was already fairly dangerous it got even more dangerous from there. After the ditch was filled the besieger could try to get on top of the wall of the besieged castle by using ladders or even siege towers.

However, both ladders and siege towers put the attacking soldiers at a disadvantage since they were usually outnumbered when they were fighting on top of the ladder or the siege tower. Additionally, the way to get to the top of the siege ladder was also dangerous since the men had to have at least one hand on the ladder. And that meant that they could either hold a weapon OR a shield in the hand that was free from holding on to the ladder.

Because of that the attempt of getting on top of the walls of a besieged fortification by using siege ladders only rarely worked out. And while siege towers had a slightly higher rate of success they were also much more expensive and could also only be used under very specific circumstances (like the flat ground).

Now one might argue that bringing a battering ram to the gate would be much easier than trying to climb up on the wall. But the gate was the part of the castle that had the heaviest fortifications. So while attempts of breaching the gate with battering rams were certainly made these attempts were usually not overly successful.

A reason for that can be found in the already mentioned fact that castles did not only have one gate. And moving the battering ram from the breached first gate to the next gate was often impeded by having a path with an angle so that the battering ram had to be turned around. Another way was that the second gate was in a position that prevented the crews of the battering ram from taking a swing which reduced the usefulness of the ram.

So since trying to get on top of the wall had limited chances of success and trying to beach the gate also had a limited chance of success another way was often preferred. And that way was to destroy a part of the wall that protected the besieged fortification.

There were basically two ways to destroy a part of the wall so that the breach could be exploited by an attack. The first way was to use ranged weapons like trebuchets. The second way was to undermine the part of the wall so that it would eventually collapse.

Let`s look at both methods.

Using ranged weapons to destroy parts of the castle walls

That is the point where ranged weapons like catapults or trebuchets and also cannons came into the picture. While long-ranged weapons like trebuchets were not used during field battles due to their disadvantages they were extremely beneficial during sieges. Do you want to find out more about how medieval battles worked? Here you can find my article with more information.

Destroying a part of the wall was more effective than trying to use siege ladders to overcome the wall. But it was also much more expensive and time-consuming and actually destroying the entire wall with the use of trebuchets was rare. Instead, trebuchets were more commonly used to destroy the top of the wall so that the enemy soldier could no longer fight from there.

While trebuchets and catapults, contrary to the cannons that came up during the 14th, could be built on the spot they still needed seasoned wood and experts to build and operate these machines.

And that made these machines not only expensive but also dependent on good logistics. Here you can find out more about the logistics of medieval warfare.

But if they were built then they were quite useful in wearing down parts of the wall of the besieged castle. And when a part of that wall finally collapsed then it was time for the waiting army to charge that breach and force its way into the fortification.

However, the besieged garrison within the castle would try to prevent the usage of these destructive machines by making surprise attacks to destroy or, even better, capture these valuable machines. Additionally, the defenders could also use their own ranged weapons to intercept the attackers from setting up and operating their siege machines.

The other way to cause the collapse of part of the walls was to undermine them.

Undermining the walls of a besieged castle to create a breach

Another, usually cheaper and faster, way to cause the collapse of parts of the wall was to undermine it.

During the Late Middle Ages miners from Lüttich, one of the only places where hard coal was mined through underground mining, were hired as sapping experts during sieges where they would dig tunnels that eventually caused the collapse of parts of the besieged castle walls.

These shafts were usually started at a safe distance from the besieged castle so that ranged weapons or surprise attacks could not harm the miners. Then the shafts were dug until they reached the foundations of the castle walls where a chamber was created while the wall foundations were propped up with timber. When the chamber was large enough it would be filled with brushwood, and timber, and since the 14th century also black power.

When the timber within the chamber burned down the fire also burned and weakened the beams that propped up the foundations of the wall. As soon as these beams gave in the part of the wall they had supported collapsed and opened a breach that could then be exploited by an attack of the besieging army. While undermining parts of the wall was probably the most effective way of creating a breach it was still expensive and also risky.

When the garrison within the besieged castle realized that a shaft was dug to undermine their wall then they would dig their own shaft with the goal of intercepting the tunnel construction of the besieger.

So I think a picture starts to get clear. Besieging a castle by either cutting it off from its supply lines or actively conquering it by force was both expensive, took a lot of time, and had a high risk of failure.

Because of that, there was one more way a castle could be captured. And that was by the capitulation of the besieged garrison.

Capitulation as a way for both sides to prevent a long, expensive, and bloody siege

Now one might think that surrendering a castle did only have an advantage for the besieger. But that was not the case!

Yes, the besieger saves time money, and blood when he did not have to capture a castle by force. But the garrison of the besieged castle also profited from a capitulation since they did not only stay alive but, depending on the conditions of Capitulation, could even leave with their possessions and weapons.

Negotiations about surrendering besieged castles to the besieger were already fairly common during the 11th century. But a capitulation was also always an evaluation of the circumstances and could bring the defenders of a besieged fortification into a quandary.

The earlier a besieged castle surrendered the better were the conditions that they could negotiate. But the defenders’ honor as warriors as well as their loyalty to their lord prohibited a premature surrender. So the besieged had to find a point of time for their surrender where they had held out for long enough that their lord could have sent help, but not so long that their position was so desperate that it would have impaired the negotiations.

As mentioned, the conditions of the surrender were up to negotiations and heavily influenced by the circumstances. When the defenders of a castle only surrendered because they could obviously no longer withstand any attack then their conditions for surrender were worse than when the defenders of a castle could still defend themselves for weeks or even months but had decided to surrender since there was no sign that their lord would send help.

Very bad conditions of surrender meant that the besieged would go into captivity while bad conditions of surrender usually allowed the defenders to leave the castle unharmed although they had to leave their belongings behind. Good conditions of surrender even allowed the leaving defenders to take their belongings and even their weapons with them.

There is actually an account from the siege of the castle La Motte-Gautier-de-Clinchamp where the 140 defenders surrendered at a point of time where they could not have kept defending the castle for long and it had become clear that their lord, King Henry I, would not send reinforcements even though he had had more than enough time.

After they had surrendered the 140 defenders of the castle could leave unharmed and with all their possessions and weapons. And even though their lord was angry about the defeat he still accepted the fact that they could not have been expected to defend the castle any longer. After all, it was not the duty of a vassal to die for his lord in a fight without any chance of success!

By the way. Since the 14th century, the agreements on the surrender of a castle were captured in written documents. Negotiating these agreements was called „capitulare“ (from the Latin word capitulum = clause in a contract).

I hope you enjoyed our trip into the Middle Ages. For more information on medieval warfare, you might want to check out my article here where I go into detail about the organization and composition of medieval armies.

Take care of yourself because you deserve it. You really do.

Until next time

Yours truly

Luke Reitzer


David S. Bachrach: Warfare in Tenth-Century Germany (Woodbridge 2012).

Malte Prietzel: Krieg im Mittelalter (Darmstadt 2006).