Curtain Wall Defenses

Until the mid-thirteenth century almost all the castles of Europe were built with the motte and bailey design, a defense system based on uncoordinated walls and towers to wear the attacker down and permit the defender many opportunities to strike back. This rarely worked, however, and the attacker more often than not simply tackled each wall separately, reducing it to rubble and then moving on to the next barrier. As time went by, fortification design techniques from the east spilled into Europe. Many new features began to be added to the existing castles and many totally new designs began to appear. The significance began to shift away from the supposedly impregnable donjon to the bailey walls, for it was wiser to keep the attackers from breaching the outer most wall, then to let him in to ravage and plunder the many buildings and storage houses on the inside of the outer bailey.

The main improvements to the fortified walls were measures allowing cover for archers, modified battlements to withstand siege engines and moving ramparts, and wide walkways (catwalks) giving free movement of large numbers of troops and knights on the walls. There still existed the main problem of sappers (miners) and siege weapons at the base of the bailey. The only solution to keeping the attackers away from the bailey wall, was not to allow the attackers to get close. This was solved by the invention and use of the merlon, which was a raised portion of a wall, with arrow slits, murder holes, and machicolations enabling full scale bombardment of warriors at the base of the fortification.

Another way to protect the wall from siege engines like the ram, pick, or screw was through the use of brattices and hoardings, a covered wooden platform built on the battlements to allow missiles and stones to be dropped through slots in the floor. These simple devices had been used since the early twelfth century, but had been overlooked because they tended to be easy targets for catapults and ballista-like weapons, but the use of the merlon and hoardings together proved an effective way of keeping attackers at bay.

The greatest advancement in castle design and fortification was the use of the flanking tower, which first began to appear in the late twelfth to early thirteenth century in parts of southern Europe. Before this time, square towers or merlons had been set even with the outer bailey, but by extending several towers outward, away from the rest of the wall, it allowed the defenders to fire from arrow slits on the sides of the towers along the length of the castle’s outer wall. This meant that the warrior did not have to expose his body to attacking archers in an attempt to shoot invaders nearing the wall.

Each flanking tower also provided cross fire for its neighbors. When the outer wall was breached, it cornered or contained the invading army into distinct regions. The first flanking towers were three-sided, with their backs open to the inner bailey, so that in the event the tower was captured by the invading force, they would prove of little worth. As time went by, the flanking towers became square and protected on all sides.

The advancements in the ability to make circular keeps also came to apply to the construction of flanking towers, and by the close of the thirteenth century most new flanking towers were cylindrical.