This is a document that was written by a dear friend of mine on the internet back in 1994, as a part of his cultural anthropology studies. He gave it to me to use, and you may quote it, provided you give proper credit to the sources.

Author: Jonathon Kerr, Queens University, Belfast, Ireland
May, 1994

 What Motives Might Have Led To Changes In Castle Design?

Abstract:

In this essay;
        I intend to look at the changes which occurred in castles in the fifty years mentioned in the title. I will look briefly at the background against which castle building was set i.e. the feudal system, and I will take a quick look the early evolution of castles. Since one of the most important aspects of castle development was their keeps, I shall include a detailed account of the evolution of keeps, and then I shall look at the other innovations which accompanied the changing face of keeps. Finally I shall look at one or two important landmarks castles, and take a quick look at a man who introduced many changes to England.

        Introduction: The most basic definition of a castle is a private fortress, created as a result of the feudal system. The feudal system grew in Western Europe after the decline of the Carolingian Empire, and was based on the personal loyalty of peasants or vassals to a king or lord in return for land or protection. In such a system those vassals came to depend on the security of a fortress to which he could retire during an attack, because lawlessness was rife under the feudal system as rival nobles strived for superiority, with the power of the king being substan-tially reduced.

        Before the Norman Conquest of 1066, this system was not in existence. After the Norman invasion, the feudal system was more or less enforced on the native Saxons, as well as the accompanying castles, as a mark of Norman authority. However, the Saxons had already determined the major characteristics of the English landscape in that the towns and villages and the clearing of woodlands, as well as the development of agriculture had already assumed a position which the Normans modified, but did not substantially alter (Cantor 1982:17). From the Norman Domesday Book, we know that the land was already divided into shires, with territorial organisation, again subdivided into hundreds of villages - 13 000 are listed in the Domesday record (Cantor 1982:17). Towns were already in existence, of which London was probably the largest, with an estimated population of at least 10 000. From the period of the Norman Conquest until around the 14th century, England experienced an economic growth, which helped fund the increasing sophistication of castles. From the 12th century on, castles, moated homesteads and fortified houses began to be built in substantial numbers.

        Castles are uniquely Middle Age buildings, and the peroga-tive of building and maintaining them lay with the Crown and nobles. In order to build a castle, a noble had to gain a license from the Crown, which prompted nobles to build castles to protect the territory that William had divided amongst them. However, castles were not the permanent homes of the barons who owned them, and were frequently only used if the lord was visiting his estate, hunting or on campaign (Cantor 1982:127).

        Castles served as more than just defensive structures, and had a number of roles. Obviously, the main function was that of a military site, particularly in earlier castles, to defend the land William had distributed. Their second major function was that of an administrative centre, overseeing lands and estates. It can be said that the proliferation of castles after the Conquest was a symbol of colonisation and cultivation, bringing new land under control. As mentioned, castles were sometimes used by lords as a base from which to hunt - there are in fact examples of such castles, which have grown up from con-verted hunting lodges, such as Gillingham in Dorset or Odiham in Hampshire.

        Early Castles: Although the main subject of this essay is the development of castles around the turn of the 13th century, I feel that it would be useful to understand, at least briefly",

       "the evolution of the castle before the 13th century. When William established himself as King of England, great numbers of castles were built - it is estimated that there were at least one hundred castles in existence before 1100 (O'Neill 1954:2), and probably many more, but evidence shows us that the ease with which they were built and rebuilt means that they were constructed mainly of wood,not stone. The most common type is what was known as the motte and bailey. The motte was a mound of earth with a flat top, surrounded by a ditch. At the top of the ditch was a wooden palisade from which the motte could be defended. Around the hill were the baileys, or court-yards, also surrounded by a ditch.

        However, even in the 11th century, more types of castles were built, with a few stone castles being erected after 1066, the most famous of which was the Tower of London,even then the chief castle of England (O'Neill 1954:6). Also known as The White Tower because of its whitewashed appearance in the Middle Ages, the Tower of London was built during the reign of William, Duke of Normandy, but took several years to build. The keep of Colchester Castle, Essex is similar to the Tower of London, and is of the same date but is even larger. As far as we know,these two keeps are the only to have been built in the 11th century - most other belong to the 12th.

        Keeps: Moving into the 12th century, the keep of Rochester Castle was build around 1130, and Ogmore too was built in the early 12th century, both characterised by their rectangu-lar keeps. The shape of keeps is an important indication of the age of a castle - earliest castles are character-ised by square or rectangular keeps, built as defensive devices, with access only from a doorway in the first floor. Rectangular keeps appear mainly to be the product of the reign of Henry II (1154 - 1189). Henry II took it on himself to destroy many castles of the previous reign,and to replaced them with keeps, which he kept for himself as royal castles, although some were built by favoured lords with the king's permission (O'Neill 1954:11).

        Rectangular keeps are characterised by three main points,which although not universal or absolute, provide a useful guide for comparison. Firstly, they are generally greater in height than in length or breadth. Secondly, they have shallow buttresses at the angles and at the centre of each side, which die away at the bottom, and finally, as already mentioned, the entrance was at the level of the first floor, and in some cases even higher.

        At around the turn of the 13th century, the number of castles had grown substantially - 350 active castles are known of in the year 1200, as opposed to just 100 a cen-tury earlier. If we allow for inaccuracy of records, and a lack of written records, it is safe to assume that there were at least 400 castles in action at the beginning of the 13th century, although this number is probably a reduction on the number of castles present thirty years earlier, when second and third generation conquerors were adding to the earliest castles established by William's generation. At around this time, rectangular keeps were gradually phased out and replaced with round keeps. One of the earliest of these is the keep of Orford Castle in Sussex (see figure five), built between 1165 and 1167,which, although earlier than some rectangular keeps, shows an advance they never display. Internally it is round,and externally it is rectangular, and has three large projecting turrets. Slightly later, the keep of Conisbor-ough Castle, Yorkshire, built from 1185-1190, is basically a circular keep, but six solid buttresses project from it,making command of the entire area possible, and providing a convenient ramp for dropping missiles on the enemy (O'Neill 1954:14). See figures one and two for examples of rectangular and round keeps respectively.

        The transition from rectangular to round, however, was not completely instantaneous - there are a few examples of transitional experimental stages, with one curved side and the remainder straight, such as the keep of Hemsley Castle in Yorkshire. Very few keeps of this kind exist, obvi-ously being made obsolete after a brief experimental period, in favour of purely round keeps.

        By the 13th century, all keeps built had at least one curved face, be they circular, semicircular or D-shaped",
        
        "and persisted for centuries, until the invention of the cannon caused dramatic modifications in castle form. One example of such a keep is Pembroke (see figure six) -possibly the best example. Pembroke was used as a base for English raids on Ireland, and was therefore a formi-dable structure. It stands 75 ft. high, and has its entrance at first floor level, like the rectangular keeps and like so many other keeps in its class. Even today is almost entirely intact, apart from the wooden floors which have long since collapsed (O'Neill 1954:15). However there are relatively few circular keeps, compared to rectangular ones because by the time they arrived, engi-neers were already moving on to concentrate on defending the curtain and completely omitting the keep. Although keeps were immensely strong, they played mostly a passive defensive role, limiting the range and number of bows that could be used from them. I will be looking later at the development of the curtain in its role in castle defence.

        The earliest round towers were built solid, such as that at Conisborough (O'Neill 1954:16), but were soon built hollow, in order to provide more accommodation, or to provide extra fighting platforms flanking the curtain. The purpose of towers more and more came to be to make the tower a stronghold by itself, by making entrance difficult (i.e. having the entrance on the first floor), by posi-tioning strong wooden doors between the towers of a cur-tain, and by forcing the enemy to pass through corridors from which the defenders could rain missiles on them. This meant that each tower of a curtain had to be taken in turn, preventing the enemy from capturing the entire curtain in one assault.

        The reason for this evolution from rectangular towers to round towers lies in simple physics, and the relative strength of each type of tower. Rectangular towers were invulnerable to most methods of siege warfare, being by their very nature immensely strong. However, they were very vulnerable to a strategy known as mining (O'Neill 1954:13). A group of sappers, protected from enemy fire would drive a gallery beneath a corner of the rectangle,inserting props as they went along. When it was com-pleted, a fire would be lit, destroying the props and causing the corner to collapse exposing the inside of the keep. A keep attacked in this way was found at Bungay Castle, Suffolk, but was probably used as a method of destroying the keep after its surrender (O'Neill 1954:12).

        There were various methods of counter attack - at Kenil-worth Castle in Warwickshire (see figure one), the but-tresses on the corners of the keeps project so far it is unlikely any gallery could penetrate them far enough to undermine them.

        However, as a general rule, the safety of rectangular towers was compromised by this technique, and was thus undesirable for the lords who owned them. The use of a curved face on the outer walls means that the keep has no vulnerable corners - the collapse of rectangular keeps was caused by the extra strain on corners - there is always a tendency for them to fall outwards at corners, therefore a wall with no angles is stronger, and the effectiveness of mines is much reduced.

        Other Innovations: During the 12th century, as stone became the normal mate-rial for castle building, with rectangular keeps, weapons and strategies became more and more complex and sophisti-cated, meaning lords had to build stronger castles to successfully defend them as well as as a statement of their wealth. The First Crusade in 1096 introduced the Western world to siege devices already used by eastern countries. The traditional siege tactics were use fire and a relentless onslaught (O'Neill 1954:8), which,although effective against wooden castles were practically useless against stone castles. The Crusaders learned to build large siege engines, which they employed as a weapon when they returned home.

        The first stage of a siege was to fill the ditch with any available material, normally under covering fire of the bows and stone throwing engines. Next, the curtain had to be breached either by a direct assault with a battering ram, or a heavy bore applied to the foundations, which may also be undermined by sappers. The defenders would reply to this by dropping heavy missiles, or flammable materials onto the attackers, who were often protected by pent-houses. One of the most famous siege engines is the belfry - a high wooden tower on wheels, which would be pushed up to the castle wall, from which the attackers could rain arrows on the top of the curtain, and gain access to the curtain. Another siege engine - a remnant of the Roman Empire was the ballista - a giant bow which hurled huge bolts at the walls. Also, the mangonel was used to hurl huge rocks and missiles at the walls. By the 13th century, these weapons were reinforced by the tre-buchet, which hurled missiles over the walls rather than at them.

        The most natural reply to the use of the belfry, ballista,mangonel and trebuchet was to build the curtain even higher. Also of great importance to the defenders was the need to control the space immediately in front of the curtain (O'Neill 1954:9), since it was from this area that most attacks took place. In France, in some cases, a gallery was constructed outwards from the top of the curtain, allowing the defenders to drop missiles on the attackers. However, in England, the most common technique was to build towers projecting from the curtain, allowing archers a line of sight to any attackers along the wall. A good example of this can be seen at Framlingham Castle,Suffolk (built 1190 - 1200), which has 13 rectangular towers projecting from the curtain, which itself is very high (O'Neill 1954:9).

        As already mentioned, as time went on, the curtain became more and more the focus of the engineers. A strong cur-tain both protected the living quarters (which were by now regularly built in the courtyard), but also allowed the defenders a much wider field of fire from which to coun-terattack. The curtain also had to be high, to make it difficult for it to be scaled, and needed towers at regu-lar intervals so that defenders could form an umbrella of flanking fire, and protect the entire base of the curtain. Since round towers are stronger than rectangular, it stands to reason that for the next two centuries, the standard tower had a curved side facing the field of attack (O'Neill 1954:16).

        During this period of development, in the early 13th century, the weakest point of any castle was still the entrance, and consequently much effort was directed towards fortifying this area. The standard 13th century gateway was an entrance with a large tower on each side,with curved sides facing outwards (O'Neill 1954:17). The ditch around the entrance was crossed by a wooden moveable bridge, sometimes called a drawbridge, but different from later bridges which were drawn up by chains. These bridges, best called turning-bridges were pivoted, like a seesaw on an axle. Heavy weights were attached to the inner end of the bridge, allowing it to swing vertical when heavy bolts which held it in place were opened.

        Inside the actual gateway, the portcullis acted as the next line of defence. It was an iron-shod wooden grille which was lowered through a slot above the gatehouse,completely barring the entrance. If this was breached, a door beyond it led to an entrance passage, which was basically a stone corridor, with holes and arrow slits from which defenders could rain missiles and combustibles on any attackers. One common myth about this era is that molten lead was poured on the attackers from above. How-ever, in the Middle Ages, lead was just as precious as it is now, and we must concur that its employment was much to expensive considering that a heavy stone could be equally unpleasant. There are a number of good examples of 13th century gatehouses, for example Pevensey Castle in Sussex or Criccieth Castle in Caernarvonshire.

       Important Castles: One of the most remarkable fortresses of the time was the English king's Fair Castle of The Rock at Chbteau-Gaillard (Normandy), which set the scene for many later, more complex structures. The castle was completed in two years between 1196 and 1198, by King Richard I. The castle had a strong tower, and a beaked plan, typical of the style of that period in France. The beaked plan meant that the castle had a strongly splayed base and prominent machicolations (openings between floors from which the defenders could assail attackers with missiles) (Platt 1982:49). However, the most significant point of design at Chbteau-Guillard was in its three successive lines of defences, having an inner, middle and outer bailey. The outer bailey was protected by a strong tower which controlled the gateway to a bridge to the middle bailey. The bridge was the only entrance to the middle bailey, which, like the outer bailey had prominent drum towers to reinforce them. Finally, the inner curtain was covered by a series of large corrugations intended to help protect the defenders when firing on the attackers (Platt 1982:49).

        Since Chbteau-Guillard was a royal castle, it is perhaps unsurprising that it was so spectacular. However, many private castles matched it in size, splendour and ingenu-ity. One such castle was that of Coucy, west of Laon (see figure three). Coucy was raised in the 1220's and 1230's and was designed by a rich nobleman (Enguerrand III) deliberately to match anything built by the king - it is said that Enguarrand himself had ambitions for the throne of France. The castle had a large round keep on its most vulnerable southern face, and drum towers at each of the four corners of the bailey. The standard design of the time was to construct the bailey and the keep as two almost independent units. Coucy castle was completely different and revolutionary in that it integrated the two components together precisely. Another new innovation at Coucy was the systematic planning of domestic accommoda-tion inside the bailey, making the courtyard an impressive sight. The keep was an imposing building, being the largest tower on the walls with the drum towers, and being surrounded by its own moat and curtain (Platt 1982:52).

        One man responsible for many of the developments around the turn of the 13th century was Hubert de Burgh (died 1234), who was the justiciar of England and earl of Kent. He was renowned as a soldier, having held castle Chinon on the Vienne against Philip Augustus in 1204 and Dover against Prince Louis in 1216. However, in this latter conflict, the castle was almost lost, and it must have been this fact which prompted him to focus his efforts on strengthening the gatehouses at the castles he built. Hubert de Burgh completely redesigned castle approaches -for example at Constable's Tower at Dover Castle (see figure four) he sealed the old gate and built a new entrance, and he provided elaborate underground works at Norfolk Towers (Platt 1982:53)

        Conclusions: It is clear to see that the years between 1175 and 1225 were very important in the history of castles, heralding many new changes and styles that were to become the norm until the introduction of the cannon until almost 300 years later. Although always becoming more and more defensive, and constantly growing stronger, we can see that the function of castles changed from being simply defensive to providing improved residential quality of the buildings of the inner ward.

        Perhaps the words of R. Allen Brown capture the essence of the castle best. He tells us that the castle was the substance of much military and therefore politi-cal power, the residence of the great, the cher-ished symbol of status and often nobility, the hub of administration and the centre in so many ways of public and private life, affecting one way or another most ranks of society through its manifold functions and the labour and service of its main-tenance. (Cantor 1982:137).

        Diagrams: (sorry, I didn't receive the diagrams with the article, as it came by email)

        Fig.1 Castles - An Introduction To The Castles Of England And Wales: O'Neil B. H. St. J., M.A., F.S.A., 1954, fig.11 A plan view of a rectangular keep (Kenilworth Castle, Warwickshire).

        Fig.2 Castles - An Introduction To The Castles Of England And Wales: O'Neil B. H. St. J., M.A., F.S.A., 1954, fig.14 A plan view of a round keep (Dolbardan Castle, Caernarvon- shire).

        Fig.3 The Castle In Medieval England And Wales: Platt,C, 1982, fig. 53 Enguerrand III's fortress at Coucy; the keep was demol- ished by the German army and has been sketched from an earlier photograph.

        Fig.4 Castles - An Introduction To The Castles Of England And Wales: O'Neil B. H. St. J., M.A., F.S.A., 1954, plate 12 Aerial photograph of Dover Castle, Kent.

        Fig.5 The Castle In Medieval England And Wales: Platt, C, 1982, fig. 41 The tower keep at Orford as it is now (left), and in plan and section (right) with the original roof lines restored.

        Fig.6 The Castle In Medieval England And Wales: Platt, C, 1982, fig. 42 Aerial photograph of Pembroke Castle.

        Bibliography:

        Cantor, L (ed), 1982: The English Medieval Landscape, London, Croom Helm

        O'Neill, B. H. St. J., M.A., F.S.A., 1954: Castles - An Introduction To The Castles Of England And Wales, London, Her Majesty's Stationery Office

        Platt, C, 1982: The castle In Medieval England And Wales, London Secker and Warburg