Why Do Castles Have Drawbridges?

Usually, the drawbridges are what you step on before entering any castle, but why do so many forts have them?

A castle drawbridge
In article about: Why Do Castles Have Drawbridges?
Picture by Tjflex2 on flickr.com

The Castles had to have a drawbridge when they were surrounded by a dip trench or a moat giving daily access to the fortress and worked as a crucial defence feature during a castle siege. It stopped the unwanted getting inside the courtyard and also protected the castle’s main gate.

Are you falling in love with castles? 

Below you will find everything you might want to know about medieval drawbridges.

The drawbridges origins 

There is evidence that Egyptians were the first who used mechanisms like drawbridges for the first time 4000 years ago.

But widespread use of drawbridges didn’t happen until the early Middle Ages, the times of the castle boom when the architects faced the challenge to enhance them with as many defence features as possible.

When they added moats to the early fortresses as the first line of defence, the habitants needed practical access inside.

This was when castle builders came up with a solution of a movable bridge, a wooden deck just long enough to reach the other bank of the moat.

It was vital for the residents to get in and out daily, but the most crucial role it played when the fort was under attack.

It made it impossible for any soldiers or war machines to reach the gates or portcullis and break them.

The early drawbridges were relatively simple, and few men could easily remove them when needed.

Later towards the 13th century, along with weapon evolution, the drawbridges became more advanced and used mechanisms like pulleys and winches to raise and lower them.

On your trips to the Castles, you might have noticed that they are restored and just working as standard bridges; only a few castles have operational drawbridges.

Types of drawbridges 

I was surprised to find out how many different movable bridges the engineers designed throughout the Middle Ages.

Here is a list of types of drawbridges and not only; 

  • Overhead crane
  • Chain and arrow drawbridge
  • Chain drawbridge without boom
  • Drawbridge without boom tilting up
  • Rigid transmission drawbridge
  • Flexible transmission drawbridge
  • Movable bridge without counterweight
  • Simple movable weighbridge
  • Modern overhead crane

Overhead crane drawbridge 

Not a pretty traditional drawbridge as we used to see, but it did have the same end goal.

This bridge would be slid out at the bottom of the gate with the help of a windlass (a horizontal barrel) until it reaches the other end of the trench.

Technicians connected the bridge with the rope or chains to the windlass and, when rotating, would start sliding the actual deck. 

You will find examples of such mechanisms at Fort de Lèvis (Canada) and Fort de Loncin (Belgium).

Chain and arrow drawbridge

One of the simplest examples where the boom had a counterweight and a chain at the back.

The back of the boom inside will be pulled down as the other end lifts the bridge with the help of the chains attached to it.

Such a drawbridge you can notice at the castles like Castle of Lassay and Chateau Pierrefonds.

Chain drawbridge without boom

This type of drawbridge is a variation of the chain and arrow drawbridge. The counterweights are suspended behind the deck beams, making it easier to raise the deck when operating the winch.

Exemples: Porte de Sens à Villeneuve-sur-Yonne (France), Château de Bonaguil (France).

Drawbridge without boom tilting up

It is one of the most uncomplicated and best systems of drawbridges used in the Middle Ages.

It consisted of a perfect balanced deck that you could lift by pulling the back end inside the building without extra arrows or booms above.

The men in charge will lower it with the help of a winch or windlass connected to the deck with chains or rope.

Moreover, it was an extremely efficient system during a siege as it didn’t have the chains and arrows exposed to artillery’s fire.

Therefore, these types of movable bridges were successfully used up until the early 18th century.

Examples; Castle of Dinan (France); Stronghold of Mornay.

Rigid transmission drawbridge

The first example of this system dates from 1697, and it was utterly perfected in 1762 by the engineer of King Alexander-Magnus of Oppenheim. 

It eliminates the frame counterweight and replaces it with metal bars weighted with cast iron sleeves. 

The coordination of movements is done only by chains passing over pulleys. A modification of the metal arms was made in 1831 by the engineer captain Romy.

Examples: 

  • Porte Saint Léon in Bayonne – Richerand-d’Obenheim system
  • Fort l’Écluse in the town of Léaz – Bélidor system
  • Fortress of Bonifacio – Belidor system modified by Delile
  • Fort Victor-Emmanuel on the Barrière de l’Esseillon in the town of Aussois – Porte contrepoids.

Flexible transmission drawbridge

Jean-Victor Poncelet designed such a system in 1820 where the counterweight of the chains acting on the apron is formed by a string of heavy links which descends into a pit as the apron rises, a manoeuvre which could be possible in a relatively small space.

A fine example of an “à la Poncelet” system can be seen at Porte Saint-Paul in Verdun (France).

Many other engineers contributed to improving this system in the following years, known as Gueze and Mangin system, Lacoste System, Deffeux System, Derché System, Devèze System.

Examples

  • The forts around Paris – Poncelet system.
  • Saint Paul de Verdun gate – Variable counterweight Poncelet system.
  • Lunette du Petit-Sainte-Foix in Sainte-Foy-lès-Lyon – Lacoste system variable counterweight
  • Porte de Secours de la Bastille in Grenoble: variable counterweights Gueze and Mangin system
  • Citadelle du Rabot in Grenoble: variable counterweights Gueze and Mangin system
  • The door of the keep of the Bastille in Grenoble: variable counterweight Deffeux system
  • Porte de Bienne in Bayonne  : Constant counterweight Derché system.
  • Fort de Troyon  : Constant counterweight Devèze system.

Movable bridge without counterweight

English lieutenant Adagt invented a simple mechanism in 1877 and installed it at the stronghold of Toul, France.

To raise the bridge, you needed to unlock the rear of the deck, which was equipped with casters descending to the bottom of the ditch by its weight, guided by two curved rails, thus raising the front permanently held to the masonry of the work.

Such a system can also be found;

Simple movable weighbridge

Again like the type mentioned above is quite an unsophisticated model, where the apron is raised using a chain rolling on rollers.

Examples:

Redoubt of Salettes in Briançon (France), 

Napoleon model towers

Modern overhead crane

The overhead crane is the successor of the medieval sliding floor. The engineer L. Mauvais proposed in 1867 a movable bridge both in weighing down and rolling. 

The main drawback of these latter movable bridges was that they required constructing unique premises for manoeuvring and surveillance.

Examples:

  • Metz Arsenal (France)
  • The entry of peace to certain forts of the second belt of Lyon (France)
  • The start of the war at certain forts in Verdun (France)

Do all castles have drawbridges?

Around 60-70% of castles existing today don’t have drawbridges; either it wasn’t a part of the initial design, or the castle didn’t have a moat or a deep trench that made it necessary to have a drawbridge.

What are the disadvantages of a castle’s drawbridge?

The disadvantage of a medieval drawbridge was in its composition. The artillery could seriously damage the wooden deck during a siege, making it difficult for the owners to restore it afterwards.

Final Thoughts 

It’s hard for us today to fully understand how vital the movable bridges were back then, but one thing we can be sure of is that they made the forts a much safer home.

If you can’t wait to admire an operating drawbridge, you might want to visit the Tower of London, Langeais Castle, Château du Taureau.

And we believe there are more that are not much advertised on the internet that is worth visiting.

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