A Castle Of The Middle Ages. Showing how the whole design arose from the requirements of the defence.
To every improvement in the method of offence there was a corresponding improvement in the method of defence. The twelfth, thirteenth and fourteenth centuries witnessed an increased efficiency in offensive engines of war—ballistas, arblasts, sows, etc. To cope with these, changes were made in the designs of castles. For example, the bases of walls were liable to attack with battering rams, etc., and the small openings in the walls made it difficult for the besieged to fire at their assailants. Machicolated galleries and bastions were consequently designed. The former were galleries built out from the top of the walls, with corbels for support. Through holes in the floors of these boiling liquid, quicklime, stones, etc. could be poured down on the besiegers. The bastion was a projecting tower which enabled the defenders to enfilade the walls.
Next came barbicans, entrance-ways whose sides sloped in towards the castle and thus forced the besiegers to pass through a strongly defended bottleneck.
Another device was to plan the approach to the entrance in such a way as to make the besiegers take a sharp turn : this made it impossible for a big body of men to force their way in by sheer weight. Gatehouse, drawbridge, timber causeway, portcullis added further to the strength of the entrance. Yet another way will be discussed-the Concentric castle.
Notice the corbels, the alur (or gallery behind the parapet ), and the roof
Many of the improvements in castle building already noted were undoubtedly due to the Crusaders. They had seen in the East the value of flanking defences, and for some time had planned so as to make the curtain wall bear more and more the brunt of attack. They had seen also a succession of concentric lines of defence, as at Constantinople, the inner higher than, and commanding the second, the second higher than and commanding the outer line.
In England during the reign of Edward I. military architecture reached its zenith, but it is erroneous to regard concentric and Edwardian as meaning the same thing, as the concentric system had been in use before the time of Edward I. Moreover, two of his castles, Carnarvon and Conway, are not concentric.
There were in England during the thirteenth century four main types of castles: (I) the shell keep ; (2) castles without keeps, in which flanking towers and curtain walls formed the sole line of defence (e.g. Carnarvon and Conway) ; (3) old castles which by extension of their sites had been given a concentric type of defence (e.g. the Tower of London, Dover Castle); (4) castles newly planned in which defences were formed by two or more concentric walls. The earliest and grandest example of this type, Caerphilly, was built in the reign of Henry III., while Edward was still in the Holy Land.
Carnarvon is in many respects the finest example of mediaeval military architecture in Europe. The plans of Carnarvon and Conway are very similar. The enclosure, in both cases an irregular polygon of an oblong shape, is divided into two wards by a cross-wall, built at a point where the curtain is drawn in slightly on both sides, and the site is consequently narrower.
Dover was first of all of the motte and bailey type. Then a keep was added, then concentric walls.
Nowhere can the beauty of the concentric plan be so well appreciated as at Beaumaris, one of Edward I’s latest Welsh castles.