One of the most effective medieval castle defences was the water-filled castle moat that completely surrounded the castle.
This created a problem as the inhabitants of the castle needed to be able to enter and leave the castle easily, the solution came in the form of an invention called a drawbridge.
Castle drawbridges were usually made of wood and had to be long enough to cover the width of the moat, early medieval drawbridges were very basic and were moved by hand, later medieval drawbridges were much more advanced and used mechanisms of pulleys and winches to raise and lower them.
Ropes and later chains were used to lower and raise the drawbridge of the castle, these chains were connected to a “windlass” which was positioned above the Gatehouses passage.
A castle Drawbridge was a heavy wooden bridge that spanned the width of a castle’s moat or ditch, the Drawbridge was movable and could be raised quickly if the castle was under attack. Man-made moats were commonly around 12 feet wide and 30 feet deep.
The drawbridge was needed so that inhabitants of a medieval castle could easily get in and out of the castle if it was surrounded by a moat, when the drawbridge was raised there was literally no way to get inside the castle easily as the castle would be completely surrounded by water.
The main gate was commonly a solid wooden door that could be strengthened with metal strips, sitting flush against the main entrance walls, later castles incorporate a gatehouse which was added to further strengthen this vulnerable part of the castle and later outposts called barbicans also further strengthened castle entrances.
The drawbridge could be quickly raised under a surprise attack making it impossible for enemies to move in their siege weapons and soldiers, the moat would create the barrier but this was impracticable without the drawbridge. Commonly a heavy wooden or metal portcullis could be dropped quickly in an emergency situation such as a surprise attack whilst the drawbridge was being fully raised.
Early medieval drawbridges were of a simple design and just used manpower to put them in place or remove them, sometimes they were destroyed and replaced. Later medieval Drawbridges were more advanced and relied on a system of ropes (later replaced by chains) and pulleys.
Large or very heavy drawbridges used counterweights to help in the raising and lowering of the drawbridge as the chains and pulleys could not cope with the weight, sometimes the portcullis (Wooden and metal-plated grille door/gate) would act as a counterweight.
The Drawbridge in later medieval times tilted up as it was closed, pulled back by thick chains, as castles were so big in later medieval times the entrances needed to be large and this meant that drawbridges were big and heavy. These later drawbridges were introduced in the 14th century and were also known as “Bascule Bridges”.
A bascule bridge is a french term for a lifting bridge such as a drawbridge is a moveable bridge that uses a counterweight mechanism!
Bascule Drawbridges needed a counterbalance to help them move them so that both ends moved in opposite directions, weights were added to help with this and the Portcullis (Metal Grilled Gate) that was positioned behind the Drawbridge was often used as a counterweight to help raise and lower the drawbridge.
You Can See a Working Drawbridge at Helmingham Hall
See a Drawbridge at Alnwick Castle