The gatehouse was one of the most fortified areas of a castle. It was also one of the more vulnerable. For this reason, engineers designed them with extra protection to keep invaders from easily breaching the castle walls.
Commonly, gatehouses consisted of a wooden gate reinforced with iron, as well as a wooden, metal grating called a portcullis. A winching mechanism above the gate controlled the portcullis and could raise and lower it via chains and slotted grooves in the side walls. Oftentimes, a gate entrance would have two of these metal grates so if attackers entered the narrow gate passage, the portcullis could be lowered at both ends, trapping the attackers inside.
Once trapped inside, it became a killing zone. Holes in the ceiling for pouring hot liquid or hot sand on the attackers and arrow slits in the walls for archers made the passageway extremely perilous. The hot sand would enter into the chinks of armor and burn the attackers. Some even more elaborate gatehouses would have a trapdoor inside with a pit of spikes below.
Yet before even reaching the gatehouse, the attackers would have to navigate a bridge or moat (often dry, sometimes filled with water) before reaching the outer castle walls. The drawbridge could also be raised and lowered via a winching mechanism within the gatehouse. Some designs even rotated the drawbridge at 90 degree angles for quicker removal.
As castles advanced and bolstered defenses even further, beyond the gatehouse and bridge and moat was another tower structure called a barbican. This outer structure was the first line of defense before attackers ever reached the gatehouse. There were many different barbican designs, but they all served one main purposes: an extra layer of defense beyond the gatehouse.
Due to the strength and fortification of the gatehouse, it was rare if a castle siege succeeded by direct attack against it. Invading armies would often try to tunnel beneath the castle walls, loosening the foundation and collapsing a section of the wall. Once a breach occurred, attackers would concentrate their efforts in that gap.
A testament to ancient engineering, many castles with their gatehouses still stand today, echoes of the past that managed to survive centuries of devastation and war.
*photo of Bodiam Castle by Antony McCallum, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.