thumb|right|300px|alt=Photo of a Spanish castle high on a rocky peninsular above a plain. It is dominated by a tall rectangular tower rising above a main building with steep slate roof. The walls are pink, and covered with a sculptural pattern. There is a variety of turrets and details.|Alcázar of Segovia in Spainthumb|300px|alt=An English castle of square plan surrounded by a water-filled moat. It has round corner towers and a forbidding appearance.|[[Bodiam Castle in Sussex, England, was described as "an old soldier's dream house" in the 1960s, although its defences are now considered more ornamental than practical.]]

A castle (from Latin castellum) is a defensive structure symbolic of the Middle Ages. The term has a history of scholarly debate surrounding its precise meaning, but a castle is usually considered to be the "private fortified residence" of a lord or noble. This is distinct from a fortress, which was not a home, or a fortified town, which was a public defence. Over the extended period of time that castles were built they took on a great many forms with many different features, but some, such as the curtain wall and arrowslits, were commonplace.

Castles originated in the 9th and 10th centuries, when the fall of the Carolingian Empire in Europe led to the division of the empire territory between individual lords and princes and an emphasis on personal defence. Castles controlled their immediate areas, and were both offensive and defensive structures; they provided a base from which raids could be launched as well as protection from an enemy. Although their military origins are often emphasised, castles also served as centres of administration and symbols of power. Urban castles were used to control the local populace and important travel routes, and rural castles were often situated near elements such as a mill, integral to life in the community.

Many castles were originally built from earth and timber, and had their defences replaced later by stone equivalents. In the late 12th and early 13th century, a scientific approach to castle defence emerged. Towers proliferated, with an emphasis on flanking fire, and many new castles were polygonal, while previously they had relied more on the lay of the land and were curvilinear, or relied on concentric defence – several stages of defence within each other that could all function at the same time, thereby maximising the castle's firepower. The origin of these changes in defence has been attributed to a mixture of influence from the Crusades – where castle technology was advanced such as the new type of concentric fortification – and drawing on earlier defences such as Roman forts for inspiration. Not all the elements of castle architecture were military in nature, and devices such as moats evolved from their original purpose of defence into symbols of power. Some grand castles had long winding approaches intended to impress, and to dominate their landscape.

Gunpowder, introduced to Europe in the 14th century, did not have an immediate impact on castle building. Castles do not show adaptation to resist bombardment by cannons until the 15th century, when artillery became powerful enough to break down walls. Although castles were built across Europe well into the 16th century, new techniques to deal with improved cannon eventually led to them becoming uncomfortable and undesirable places to live, and so true castles went into decline, replaced by artillery forts with no role in administration, and country houses that were indefensible. From the 18th century onwards, there was a renewed interest in castles with the construction of mock castles, part of a romantic revival of Gothic architecture, but they had no defensive purpose.

Definition

Etymology

thumb|300px|alt=The keep of the Tower of London, seen rising from the Thames River, rising behind the Traitor's Gate. The keep is large, square in plan, and has four corner towers, three square and one round, all topped by lead cupolas| The Norman "White Tower", the [[keep of the Tower of London, exemplifies all uses of a castle: city defence, a residence, and a place of refuge in times of crisis.]]

Castle is derived from the Latin word castellum. This is a diminutive of the word castrum, which means "fortified place". The Old English castel, French château, Spanish castillo, Italian castello, as well as other European words for castle derive from castellum. The word castle was introduced into English shortly before the Norman Conquest to denote this type of building, then new to England. Although the various terms used for castles in Europe derive from the same root, they are not universally applied to the same types of structures. The French château is used to describe a grand country house at the heart of an estate, regardless of the presence of fortifications.

Defining characteristics

In its simplest terms, the definition of a castle accepted amongst academics is "a private fortified residence". This contrasts with earlier fortifications, such as Anglo Saxon burhs and walled cities such as Constantinople and Antioch in the Middle East: castles were not communal defences but were built and owned by the local feudal lord, either for themselves of for their monarch. In the late 20th century, there was a trend to refine the definition of a castle by including the criterion of feudal ownership, thus tying castles to the medieval period. However, this does not necessarily reflect what medieval people called castles. During the First Crusade (1096–1099) the Frankish armies encountered walled settlements and forts that they indiscriminately called castles, but would not be considered such under the modern definition.
thumb|left|300px|alt=Windsor Castle, seen at the end of a long avenue, lit pink by the sunset. The castle gives an impression of tremendous size, and has an imposing, twin-towered gatehouse and, to the left, a large round keep.|[[Windsor Castle in England was first built as a fortification of the Norman Conquest, and today is home to Queen Elizabeth II of the United Kingdom.]]
Castles served a range of purposes, the most important of which were military, administrative, and domestic. As well as defensive structures, castles were also offensive tools which could be used as a base of operations in enemy territory. Castles were established by Norman invaders of England as both defensive and offensive tools to pacify the inhabitants. As William the Conqueror advanced through England after the Norman Conquest in 1066, he fortified key positions to secure the land he had taken. Between 1066 and 1087 he established 36 castles such as Warwick Castle, which was used to guard against rebellion in the English Midlands. However, a recent trend to view castles less as military institutions and more as social structures has questioned the current definition. During the Middle Ages, castles tended to lose their military significance and became more important as residences and statements of power.

In Britain the term "castle" has also been erroneously used to refer to Iron Age fortifications such as Maiden Castle, Dorset. A castle was not only a bastion and prison but also a place where a knight or lord could entertain his peers. Over time the aesthetics of the design became more important, as the castle's appearance and size began to reflect the prestige and power of its occupant. Comfortable homes were often fashioned within their fortified walls. Although castles still provided protection from low levels of violence in later periods, eventually they were succeeded by country houses as high status residences.

Common features

Motte

thumb|right|300px|alt=A small castle comprising a round keep surrounded by a tall encircling wall on top of a man-made hill.|The wooden palisades surmounting mottes were often later replaced in stone, as in this example at Château de Gisors in France.
A motte was a mound with a flat top. They were often artificial, although sometimes incorporated a pre-existing feature of the landscape. The excavation of earth for the mound would leave a ditch around the motte, which acted as a further defence. Sometimes a nearby stream would be diverted to flood the ditch, creating a moat. Motte and moat derive from the same Old French word, indicating that they were originally associated features and depended on each other for their construction. Although the motte is usually associated with the bailey to form a motte-and-bailey castle, this was not always the case and there are instances where a motte existed on its own. "Motte" refers to the mound alone, but it was often surmounted by a fortified structure, such as a keep, and the flat top would be surrounded by a palisade. The motte was accessed by a flying bridge as represented by the Bayeux Tapestry's depiction of Château de Dinan. Sometimes a motte covered an older castle or hall, whose rooms now became underground storage areas and prisons beneath a new donjon.

Bailey and enceinte

A bailey, also called a ward, was a fortified enclosure. They were a common feature of castles, and most had at least one. The keep on top of the motte was the domicile of the lord in charge of the castle and a bastion of last defence, while the bailey was the home of the rest of the lord's household and gave them protection. The barracks for the garrison, stables, workshops, and storage facilities could all be expected to be found in the bailey. There was a progression for lords to build more comfortable accommodation for themselves within the bailey, which resulted in the creation of another bailey that separated the high status buildings – such as the lord's chambers and the chapel – from the everyday structures such as the workshops and barracks. Although often associated with the motte-and-bailey type of castle, baileys could be found as independent defensive structures. These simple fortifications were called ringworks. The terms bailey and enceinte are linked, as the enceinte was the castle's main defensive enclosure. A castle could have several baileys but only one enceinte. Castles with no keep and which relied on their outer defences for protection are sometimes called enceinte castles; these were the earliest form of castles, before the donjon arrived in the 10th century.

Keep

A keep was a great tower and usually the strongest point of a castle before the introduction of concentric defence. Keep was not a term used in the medieval period – the term was applied from the 16th century onwards – and donjon was used to refer to great towers, or turris in Latin. Dungeon is a corrupted form of donjon and means a dark, unwelcoming prison. Although often the strongest part of a castle and a last place of refuge if the outer defences fell, the keep was not left empty in case of attack but was used as a residence by the lord who owned the castle, or his guests or representatives. Initially this was only the usual pattern in England, when after the Norman Conquest of 1066 the "conquerors lived for a long time in a constant state of alert"; elsewhere the lord's wife presided over a separate residence (domus, aula or mansio in Latin) close to the keep, and the donjon was a barracks and headquarters. Gradually the two functions merged into the same building; for many examples choosing the appropriate term can be difficult, and the highest residential storeys have large windows. In motte-and-bailey castles, the keep was on top of the motte.

Curtain wall

thumb|right|300px|alt=An angle view of the exterior walls of a grim fortress|Carcassonne, France, showing the classic features of the curtain walls, defensive ditch with arched bridge, and cylindrical flanking towers, with a gatehouse and additional wooden defensive structures.
Curtain walls were defensive walls enclosing a bailey. They had to be high enough to make scaling the walls with ladders difficult and thick enough to withstand bombardment from siege engines which from the 15th century onwards included artillery. A typical wall could be wide and tall, although sizes varied greatly between castles. To protect them from undermining, curtain walls were sometimes given a stone skirt around their base. Walkways along the tops of the curtain walls allowed defenders to rain missiles on enemies from above, and battlements gave them further protection. Curtain walls would be studded with towers to allow enfilading fire along the wall. Arrowslits in the walls did not become common in Europe until the 13th century, for fear that they might compromise the wall's strength.

Moat

A moat was a defensive ditch with steep sides, and could be either dry or filled with water. Its purpose was to stop engines such as siege towers from reaching the curtain wall and to prevent the walls from being undermined. Water moats are found in low lying areas. Moats were often crossed by a drawbridge, although these were often replaced by stone bridges. The moat around Flint Castle in Wales was dug by 1,800 workers. Fortified islands could be added to the moat, adding another layer of defence. Water defences, including moats as well as natural lakes, had the benefit of dictating the enemy's approach to the castle. The 13th-century Caerphilly Castle in Wales has some of the largest water defences in Western Europe; the site covers over and the defences were created by flooding the valley to the south of the castle.

Gatehouse

An undeveloped entrance is the weakest part in a circuit of defences. To overcome this, the gatehouse was developed, allowing those inside the castle to control the flow of traffic. In earth and timber castles, the gateway was usually the first feature to be rebuilt in stone. The front of the gateway was a blind spot, so to allow the defenders to see the gate without exposing themselves projecting towers were added on each side of the gate, in a style similar to that developed by the Romans. Contained within the building would be a series of defences to make a direct assault more difficult than battering down a simple gate. There would be one or more portcullis – a wooden grille reinforced with metal to block a passage – and arrowslits to allow defenders to harry an enemy. The passage through the gatehouse would have been lengthened to increase the amount of time an assailant had to spend under fire in a confined space and unable to retaliate. It is a popular myth that so-called murder-holes – openings in the ceiling of the gateway passage – were used to pour boiling oil or molten lead on attackers; the price of oil and lead, and the distance of the gatehouse from fires meant that this was completely impractical. They were most likely used to drop objects on attackers, similar to machicolations or to pour water to extinguish fires. Provision was made in the upper storey of the gatehouse for accommodation, so the gate was never left undefended, although this evolved to become more comfortable at the expense of defence. The entrance to a castle could be further elaborated through the addition of a barbican. This consisted of a rampart and ditch in front of the gatehouse. Developed in the 13th and 14th centuries, it could also include a tower. The purpose of a barbican was not just to provide another line of defence but to dictate the only approach to the gate.

Other features

Battlements were most often found surmounting curtain walls, although also on the tops of gatehouses, and comprised several elements; crenellations, hoardings and machicolations, and loopholes. Crenellation is the collective name for alternating crenels and merlons: gaps and solid blocks on top of a wall. Hoardings were wooden constructs that projected beyond the wall, allowing defenders to shoot at or drop objects on attackers at the base of the wall without having to lean perilously over the crenellations, thereby exposing themselves to retaliatory fire. Machicolations were stone openings in the top of the wall that allowed objects to be dropped on an enemy at the base off the wall in a similar fashion to hoardings. Arrowslits, also commonly called loopholes, were narrow vertical openings in defensive walls which allowed arrows or crossbow bolts to be fired on attackers. The narrow slits were intended to protect the defender by providing a very small target, but the size of the opening could also impede the defender if it was too small. A smaller horizontal opening could be added to give an archer a better view for aiming.

History

Antecedents

thumb|240px|alt=An archaeological drawing of the site of an ancient fort, showing rectangular plan, palisades, corner towers and layout of buildings being excavated.||Roman fort, England/" class="wiki">Ambleside Roman fort, England
Historian Charles Coulson states that the accumulation of wealth and resources such as food in ancient societies led to the need for defensive structures. The earliest fortifications originate in the Fertile Crescent, the Indus Valley, Egypt, and China where settlements were protected by large walls. Northern Europe was slower than the east to develop defensive structures and it was not until the Bronze Age that hill forts were developed, which proliferated across Europe in the Iron Age. They differed to their eastern counterparts through the use of earthworks rather than stone as a building material. Many earthworks survive today, along with evidence of palisades to accompany the ditches. In Europe, oppida emerged in the 2nd century BC; they were densely inhabited fortified settlements, such as the oppidum of Manching, and developed from hill forts. The Romans encountered fortified settlements such as hill forts and oppida when expanding their territory into northern Europe. Although primitive, they were often effective, and required extensive siege engines and other siege warfare techniques to overcome, such as at the Battle of Alesia. The Romans' own fortifications (castra) varied from simple temporary earthworks thrown up by armies on the move, to elaborate permanent stone constructions, notably the milecastles of Hadrian's Wall. Roman forts were generally rectangular with rounded corners – a "playing-card shape".

Origins and early castles

Like the feudal society they were part of, castles had their origins in the 9th and 10th centuries. This period saw the emergence of a social and military elite in the Carolingian Empire and the development of mounted fighting. Fighting on horseback was a costly and time consuming endeavour, requiring specialised equipment and trained horses, and for their efforts these early knights were granted land by the lords for whom they fought. The link between knight and lord was the basis of feudalism, and could go higher up the social scale with loyalties between lords, dukes, princes, and kings. When the Carolingian Empire collapsed in the 9th and 10th centuries, it took with it effective centralised administration, and it fell to the landed elite to take over control. This led to the privatisation of government, with local lords taking on the responsibility for the local economy and justice. Although castles were private buildings, lordship was a public office and the holder had a responsibility to protect his peasants. There is a traditional view that feudalism was a tool of social disintegration that contributed to the downfall of the Carolingian Empire, however modern academic opinion is that it was a successor to previous government rather than a rival. Castles sometimes required the permission of the king or other high authority. Charles the Bald prohibited the construction of castles without his permission and ordered them destroyed; this could be the earliest reference to castles being built without permission, breaking the feudal agreement between lord and vassal, however there are very few castles dated with certainty from the mid-9th century. Converted into a donjon in around 950, Doué-la-Fontaine, in France, is the oldest standing castle in Europe.
thumb|350px|left|alt=A section of an embroidered cloth showing a castle on a hilltop being defended by soldiers with spears while two soldiers in armour are attempting to set fire to the palisade.|One of the earliest representations of a castle from the [[Bayeux Tapestry. It depicts attackers of Château de Dinan in France using fire, one of the threats to wooden castles.]]
Military historian Allen Brown asserts that in the absence of a working state and the breakdown of society associated with the decline of the Carolingian Empire, feudal ties became more important. The rise of castles is not solely attributed to defence of the new feudal lords’ lands, but as a reaction to attacks by Magyars, Muslims, and Vikings. It is likely that the castle evolved from the practice of fortifying a lordly home. In a time of social unrest, a lord would wish to protect his home or hall, and the greatest threat was that of fire as they were usually wooden. To protect against this, and keep other threats at bay, there were several courses of action available: create encircling earthworks to keep an enemy at a distance; build the hall in stone; or raise it up on an artificial mound, known as a motte, to present an obstacle to attackers. While the concept of ditches, ramparts, and stone walls as defensive measures is ancient, raising a motte to exploit the advantages of height is a medieval innovation. A bank and ditch enclosure was a simple form of defence, and when found without an associated motte is called a ringwork; when the site was in use for a prolonged period, it was sometimes replaced by a more complex structure or enhanced by the addition a stone curtain wall. Building the hall in stone did not necessarily make it immune to fire as it still had windows and a wooden door. This led to the elevation of windows to the first floor – to make it harder to throw objects in – and to change the entrance from ground floor to first floor. These features are seen in many surviving castle keeps, which were the more sophisticated version of halls and contained the lord’s household. Castles were not just used as defensive sites, but to enhance a lord’s control over his lands. They allowed the garrison to control the surrounding area, and formed a centre of administration, providing the lord with a place to hold court.

References to castles in texts such as charters from 1000 onwards increased greatly. Historians have interpreted this as evidence of a sudden increase in the number of castles in Europe around this time; their interpretation has been supported by archaeologists dating the construction of castle sites through the examination of ceramics. The increase in Italy began in the 950s, with numbers of castles increasing by a factor of three to five every 50 years, whereas other parts of Europe such as France and Spain were slower. In 950, Provence was home to 12 castles, by 1000 this figure had risen to 30, and by 1030 it was over 100. Despite the common period in which castles rose to prominence in Europe, their form and design varied from region to region. In the early 11th century, the motte – an artificial mound surmounted by a palisade and tower – was the most common form of castle in Europe, aside from Scandinavia. Castles were introduced into England shortly before the Norman Conquest in 1066. The motte and bailey – a motte with an outer enclosure – remained the dominant form of castle in England, Wales, and Ireland well into the 12th century. At the same time, castle architecture in mainland Europe became more sophisticated.
thumb|right|300px|alt=A Square building of grey stone with narrow vertical slits on the first floor, and wider windows on the second. The top of the castle looks decayed and there is no roof, except over a tower attached to the keep.|Built in 1138, [[Castle Rising Castle|Castle Rising in England is an example of an elaborate donjon.]]
The donjon – or great tower – was at the centre of this change in castle architecture in the 12th century. Central towers proliferated, and typically had a square plan, with walls thick. Their decoration emulated Romanesque architecture, and sometimes incorporated double windows similar to those found in church bell towers. Donjons, which were the residence of the lord of the castle, evolved to become more spacious. The changes in design changed from utilitarian to decorative to impose upon the landscape as a symbol of lordly power, sometimes compromising defence for the sake of display. Historians have interpreted the widespread presence of castles across Europe in the 11th and 12th centuries as evidence that warfare was common, and usually between local lords.

In some countries, it was necessary to obtain the permission of the king through a licence to crenellate, or else the builder risked it being slighted. This was not universal, as in some countries, the monarch had little control over lords, or required the construction of new castles to aid in securing the land – as was the case in England after 1066 and the Holy Land during the Crusades – so was unconcerned about granting permission. Switzerland is an extreme case of there being no state control over who built castles, and as a result there are 4,000 in the country. Before the 12th century, castles were as uncommon in Denmark as they had been in England before the Norman Conquest. The introduction of castles to Denmark was a reaction to attacks from Wendish pirates, and they were usually intended as coastal defences.

Innovation and scientific design

Until the 12th century, stone-built and earth and timber castles were contemporary, but by the late 12th century the number of castles being built went into decline. This has been partly attributed to the higher cost of stone-built fortifications, and the obsolescence of timber and earthwork sites, which meant it was preferable to build in more durable stone. Although superseded by their stone successors, timber and earthwork castles were by no means useless. This is evidenced by the continual maintenance of timber castles over long periods, sometimes several centuries; at the start of the 15th century Owain Glyndŵr’s castle at Sycharth, founded in the late 11th century, was a timber structure.

In the late 12th century, there was an obvious change in castle architecture. Until then, castles probably had few towers; a gateway with few defensive features such as arrowslits or a portcullis; a great keep or donjon, usually square and without arrowslits; and the shape would have been dictated by the lay of the land, and the result was often irregular or curvilinear. The design of castles was of course not uniform, but these were features that could be found in a typical castle in the mid-12th century. By the end of the 12th century or the early 13th century, a newly constructed castle could be expected to be polygonal in shape, with towers at the corners to provide enfilading fire for the walls. The towers would have protruded from the walls and featured arrowslits on each level to allow archers to target anyone nearing or at the curtain wall. These later castles would not always have a keep, but this may have been because the more complex design of the castle as a whole drove up costs and the keep was sacrificed to save money. The larger towers provided space for habitation to make up for the loss of the donjon. Where keeps did exist, they were no longer square but polygonal or cylindrical. Gateways were more strongly defended, with the entrance to the castle usually between two half-round towers which were connected by a passage above the gateway – although there was great variety in the styles of gateway and entrances – and one or more portcullis.
thumb|left|240px|alt=Two round towers of light yellow stone at the bottom and darked orangy stone at the top on either side of an arched entrance. A bridge leads from the entrance to allow access.|The gatehouse to the inner ward of Beeston Castle, England, was built in the 1220s and has an entrance between two half-round towers.
When seeking to explain this change in the complexity and style of castles, antiquarians found their answer in the Crusades. It seemed logical that the Crusaders had learned much about fortification from their conflicts with the Saracens and exposure to Byzantine architecture. There were legends such as that of Lalys – an architect from Palestine who reputedly went to Wales after the Crusades and greatly enhanced the castles in the south of the country – and it was assumed that great architects such as James of Saint George originated in the East. However, in the mid-20th century this view was cast into doubt. Legends were discredited, and in the case of James of Saint George, it was proven that he came from Saint-Georges-d'Espéranche, in France. If the innovations in fortification had derived from the East, it would have been expected for their influence to be seen from 1100 onwards, immediately after the Christians were victorious in the First Crusade (1096–1099), rather than nearly 100 years later. Roman remains in western Europe were still upstanding in many places, and as they too featured flanking round-towers, and entrances between two flanking towers. The castle builders of western Europe were aware of and influenced by Roman design as demonstrated by the reuse of Saxon shore forts in England, a late Roman innovation despite their name, and in Spain the wall around the city of Avila imitated Roman architecture when it was built in 1091. It has been argued – by historian Smail in Crusading warfare – that the case for the influence of eastern fortification on the west has been overstated, and that crusaders of the 12th century in fact learnt very little about scientific design from Byzantine and Saracen defences. The explanation for this is that a well sited castle that made use of natural defences and had strong ditches and walls had no need for a scientific design. An example of this approach is Karak Castle. Although there were no scientific elements to its design it was almost impregnable, and in 1187 Saladin chose to lay siege to the castle and starve out its garrison rather than risk an assault.
After the First Crusade, Crusaders who did not return to their homes in Europe helped found the Crusader states of the principality of Antioch, the County of Edessa, the Kingdom of Jerusalem, and the County of Tripoli. The castles they founded to secure their acquisitions were designed mostly by Syrian master-masons. Their design was very similar to a Roman fort or Byzantine tetrapyrgia: a square curtain wall with towers in each corner, also usually square and not projecting much beyond the curtain wall. In the interior, the keep would have had a square plan and generally be undecorated. While castles were used to hold a site and control movement of armies, in the Holy Land some key strategic positions were left unfortified. Castle architecture in the East became more complex around the late 12th and early 13th century after the stalemate of the Third Crusade (1189–1192). Both Christians and Muslims created fortifications, and the character of each was different. Saphadin, the 13th-century ruler of the Saracens, created structures with large rectangular towers that influenced Muslim architecture and were copied again and again, however they had little influence on Crusader castles.
thumb|300px|alt=A drawing of a stone castle with two high curtain walls, one within the other. They are crenelated and studded with projecting towers, both rectangular and rounded. The castle is on a promontory high above the surrounding landscape.|right|Krak des Chevaliers is a concentric castle built with both rectangular and rounded towers. It is one of the best preserved Crusader castles.
In the early 13th century, Crusaders castles were mostly built by Military Orders, such as the Knights Hospitaller, Knights Templar, and Knights of the Teutonic Order. They were responsible for the foundation of sites such as Krak des Chevaliers, Margat, and Belvoir. The forms of the castle varied not just between orders, but individually from castle to castle, although it was common for the castles founded in this period to have concentric defences. The concept, which originated in castles such as Krak des Chevaliers, was to remove the reliance on a central strongpoint and to emphasise the defence of the curtain walls. There would be more than one ring of defensive wall, one inside the other, with the inner ring rising above the outer so that its field of fire was not completely obscured. If an assailant made it past the first line of defences into the outer enclosure, they would be caught in the killing ground between the inner and outer walls and have to assault the second wall to secure the fall of the castle. Concentric castles were widely copied across Europe, for instance when Edward I of England – who had himself been on Crusade – built castles in Wales in the late 13th century, four of the eight he founded were concentric. Not all the features of the Crusader castles from the 13th century were emulated in Europe; for instance, it was common in Crusader castles to have the entrance in the side of a tower and for there to be two turns in the passageway, lengthening the time it took for someone to reach the outer enclosure. It is rare for this feature to be found in Europe.
It was common for castles in the East to have arrowslits in the curtain wall at multiple levels; something that contemporary builders in Europe were wary of, believing that they weakened the wall's structural integrity. Arrowslits did not compromise the wall's strength, but it was not until Edward I's programme of castle building that they were adopted in Europe. The Crusades also led to the introduction of machicolations into western architecture. Until the 13th century, the tops of towers had been surrounded by wooden galleries, allowing defenders to drop objects on assailants below. Although machicolations performed the same purpose as the wooden galleries, they were probably an Eastern invention rather than an evolution of the wooden form. Machicolations were used in the East long before the arrival of the Crusades, and perhaps as early as the first half of the 8th century in Syria.

Although France has been described as "the heartland of medieval architecture", the English were at the forefront of castle architecture in the 12th century. French historian Francois Gebelin said: "The great revival in military architecture was led, as one would naturally expect, by the powerful kings and princes of the time; by the sons of William the Conqueror and their descendants, the Plantagenets, when they became dukes of Normandy. These were the men who built all the most typical twelfth-century fortified castles remaining to-day". Despite this, by the beginning of the 15th century, the rate of castle construction in England and Wales went into decline; the new castles were generally of a lighter build than earlier structures and presented few innovations, although strong sites were still created such as that of Raglan in Wales. At the same time, French castle architecture came to the fore and led the way in the field of medieval fortifications. Across Europe – particularly the Baltic, Germany, and Scotland – castles were built well into the 16th century.

Advent of gunpowder

Artillery powered by gunpowder was introduced to Europe in the 1320s and spread quickly. Handguns are not recorded until the 1380s and were unpredictable and inaccurate weapons. Castles were adapted to allow small guns – averaging between  – to fire from towers. These guns were too heavy for a man to carry and fire, but if he supported the butt end and rested the muzzle on the edge of the gun port he could fire the weapon. The gun ports developed in this period show a unique feature, that of a horizontal timber across the opening. A hook on the end of the gun could be latched over the timber so the gunner did not have to take the full recoil of the weapon. This adaptation is found across Europe, and although the timber rarely survives, there is an intact example at in Doornenburg Castle in Denmark. Gunports were keyhole shaped, with a circular hole at the bottom for the weapon and a narrow slit on top to allow the gunner to aim.
thumb|left|300px|alt=A dark grey, stone round tower with crennelations and machicolations on top and a skirt at the bottom.|The rounded towers of Sarzana Castle in Italy are adapted to gunpowder.
This form is very common in castles adapted for guns, found in Egypt, Italy, Scotland, and Spain, and elsewhere in between. Other types of port, though less common were horizontal slits – allowing only lateral movement – and large square openings, which allowed greater movement. The use of guns for defence gave rise to artillery castles, such as that of Château de Ham in France, Defences against guns was not developed until a later stage. Ham is an example of the trend for new castles to dispense with earlier features such as machicolations, tall towers, and crenellations.

Bigger guns were developed, and in the 15th century became an alternative to siege engines such as the trebuchet. The benefits of large guns over trebuchets – the most effective siege engine of the Middle Ages before the advent of gunpowder – were those of a greater range and greater power. In an effort to make them more effective, guns were made bigger and bigger. By the 1450s guns were the preferred siege weapon, and their effectiveness was demonstrated by Mohammed II at the Siege of Constantinople. The response towards more effective cannons was to build thicker walls than in previous castles and to prefer round towers as the curving sides were more likely to deflect a shot than a flat surface. While this sufficed for new castles, pre-existing structures had to find a way to cope with being battered by cannon. An earthen bank could be piled behind a castle's curtain wall to absorb some of the shock of impact. Often, castles constructed before the age of gunpowder would be incapable of using guns as their wall-walks were too narrow. A solution to this was to pull down the top of a tower and to fill the lower part with the rubble to provide a surface for the guns to fire from. Lowering the defences in this way had the effect of making them easier to scale with ladders. A more popular alternative defence, which avoided damaging the castle, was to establish bulwarks beyond the castle's defences. These could be built from earthier earth or stone and were used to mount weapons.

Around 1500, the innovation of the angled bastion over curved was developed in Italy. The elite who were responsible for castle construction were forced to choose between the new type which could withstand cannon-fire but as a result was ugly and uncomfortable to live in, or to stick with an earlier more elaborate style with had more aesthetic appeal and was more of a status symbol. The second choice was more popular, and while the castle retained its use as a status symbol, it became apparent that earlier fortifications were unable to stand up to cannons, and so there was no point in trying to make the site genuinely defensible.
thumb|right|240px|alt=A low, two-storey building with a crenelated frontage. A four storey crenelated tower is in the centre of the frontage.|Fortaleza Ozama in the Dominican Republic was the first castle built in the Americas
However, some true castles were built in the Americas by the Spanish, English, and French colonies. The first stage of Spanish fort construction has been termed the "castle period", which lasted from 1492 until the end of the 16th century. Starting with Fortaleza Ozama, "these castles were essentially European medieval castles transposed to America." Among other defensive structures (including forts and citadels), castles were also built in New France towards the end of the 17th century. Where artillery was not as developed as on the battle-fields of Europe, some of Montreal's outlying forts were built like the fortified manor houses of France. Fort Longueuil, built from 1695–1698 by a baronial family, has been described as "the most medieval-looking fort built in Canada". The manor house and stables were within a fortified bailey, with a tall round turret in each corner. The "most substantial castle-like fort" near Montréal was Fort Senneville, built in 1692 with square towers connected by thick stone walls, as well as a fortified windmill. Stone forts such as these served as defensive residences, as well as imposing structures to prevent Iroquois incursions.

Although castle construction faded towards the 16th century, they did not necessarily all fall out of use. Some retained some role in local administration and became law courts, while others are still handed down in aristocratic families as hereditary seats. A particularly famous example of this is Windsor Castle in England which was founded in the 11th century and is home to the monarch of the United Kingdom. In other cases they still had a role in defence. Tower houses, which are closely related to castles and include pele towers, were defended towers that were permanent residences built in the 14th to 17th centuries. Especially common in Ireland and Scotland, they could be up to five storeys high and succeeded common enclosure castles and were built by a greater social range of people. While unlikely to provide as much protection as a more complex castle, they offered security against raiders and other small threats.

Later use and revival castles

According to archaeologists Oliver Creighton and Robert Higham, "the great country houses of the seventeenth to twentieth centuries were, in a social sense, the castles of their day". Although there was a trend for the elite to move from castles into country houses in the 17th century, castles were not completely useless. In later conflicts, such as the English Civil War (1641–1651), many castles were refortified, although subsequently slighted to prevent them from being used again.
thumb|left|240px|alt=A tall building in white stone, surrounded by trees and high above the surrounding landscape. The building has lots of windows and several towers with peaked blue roofs.|[[Neuschwanstein Castle|Neuschwanstein is a 19th-century neo-romantic castle built by Ludwig II of Bavaria.]]
Artificial ruins became popular in the 18th century as a manifestation of a romantic interest in the Middle Ages and chivalry, and as part of the broader Gothic Revival in architecture. They were usually built as centre pieces in aristocratic planned landscapes. Follies were similar, although differed from artificial ruins in that they were not part of a planned landscape, but rather seemed to have no reason for being built. Both drew on elements of castle architecture such as castellation and towers, but they served no military purpose and were solely for display. Revival or mock castles, most of which were country houses, were particularly common in the British Isles, for example Belvoir Castle and Eastnor Castle in England and Castell Coch in Wales. Edwin Lutyens' Castle Drogo (1911–1930) was the last flicker of this movement in England. Also, the 19th-century Neuschwanstein is one such revival castle in Germany.

Construction

thumb|right|alt=A half finished circular tower with scaffolding near the top. There are holes in the tower and workers on top.|Construction of a large tower, with scaffolding and masons at work. The holes mark the position of the scaffolding in earlier stages of construction.
Once the site of a castle had been selected – whether a strategic position or one intended to dominate the landscape as a mark of power – the building material had to be selected. An earth and timber castle was cheaper and easier to erect than one built from stone. The costs involved in construction are not well recorded, and most surviving records relate to royal castles. A castle with earthen ramparts, a motte, and timber defences and buildings could have been constructed by an unskilled workforce. The source of man-power was probably from the local lordship, and the tenants would already have the necessary skills of felling trees, digging, and working timber necessary for an earth and timber castle. Possibly coerced into working for their lord, the construction of an earth and timber castle would not have been a drain on a client’s funds. In terms of time, it has been estimated that an average sized motte – high and wide at the summit – would have taken 50 people about 40 working days. An exceptionally expensive motte and bailey was that of Clones in Ireland, built in 1211 for £20. The high cost, relative to other castles of its type, was because labourers had to be imported.
Although their cost varied according to factors such as their complexity and transport costs for material, it is certain that stone castles cost a great deal more than those built from earth and timber. Even a very small tower, such as Peveril Castle, would have cost around £200. In the middle were castles such as Orford, which was built in the late 12th century for £1,400, and at the upper end were those such as Dover, which cost about £7,000 between 1112 and 1191. Spending on the scale of the vast castles such as Château Gaillard (an estimated £15,000 to £20,000 between 1196 and 1198) was easily supported by The Crown, but for lords of smaller areas, castle building was a very serious and costly undertaking. It was usual for a stone castle to take the best part of a decade to finish. The cost of a large castle built over this time (anywhere from £1,000 to £10,000) would take the income from several manors, severely impacting on a lord’s finances. Cost in the late 13th century were of a similar order, with castles such as Beaumaris and Rhuddlan costing £14,500 and £9,000 respectively. Edward I’s campaign of castle-building in Wales cost £80,000 between 1277 and 1304, and £95,000 between 1277 and 1329. Renowned designer Master James of Saint George, responsible for the construction of Beaumaris, explained the cost:

Not only were stone castles expensive to build in the first place, but their maintenance was a constant drain. They contained a lot of timber, which was often unseasoned and as a result needed careful upkeep. Castles such as Exeter and Gloucester were often given figures of between £20 and £50 annually in the late 12th century for constant repairs.
left|thumb|400px|alt=An orange brick castle with a curtain wall and a central keep. The gateway is flanked by two round towers with high peaked roofs. Aside from the keep, there is another building within the castle rising above the curtain wall.|The [[Malbork Castle|Castle of the Teutonic Order in Malbork, Poland, is an example of brick-built castle and was built in a style different to that of castles in western Europe and the Near East.]]
Medieval machines and inventions, such as the treadwheel crane, became indispensable during construction, and techniques of building wooden scaffolding were improved upon from Antiquity. Finding stone for shell keeps and castle walls was the first concern of medieval builders, and a major preoccupation was to have quarries close at hand. There are examples of some castles where stone was quarried on site, such as Chinon, Château de Coucy and Château Gaillard.
Brick-built structures were not necessarily weaker than their stone-built counterparts. In England, brick production proliferated along the south-east coast due to an influx of Flemish weavers and a reduction in the amount of available, leading to a demand for an alternative building material. Brick castles are less common than stone or earth and timber constructions, and often it was chosen for its aesthetic appeal or because it was in fashion, encouraged by the brick architecture of the Low Countries. For example, when Tattershall Castle was built between 1430 and 1450, there was plenty of stone available nearby, however the owner, Lord Cromwell, chose to use brick. About 700,000 bricks were used to built the castle, which has been described as "the finest piece of medieval brick-work in England". Brick castles were predominant in Scandinavia and the Baltic; Denmark had few quarries, and as a result, most of its castles are earth and timber affairs, or later on built from brick.

Social centre

right|thumb|alt=A woman dressed in yellow handing tying a piece of red cloth to the arm of a man dressed in armour and mounted on a horse.|God Speed! by Edmund Blair Leighton, 1900: a late Victorian view of a lady giving a favour to a knight about to do battle
Due to the lord's presence in a castle, it was a centre of administration from where he controlled his lands. He relied on the support of those below him, as without the support of his more powerful tenants, a lord could expect his power to be undermined. Successful lords regularly held court with those immediately below them on the social scale, but absentee lords found their power weakened. Larger lordships could be vast, and it would be impractical for a lord to visit all his properties regularly so deputies were appointed. This especially applied to royalty, who sometimes owned land in different countries. To allow the lord to concentrate on his duties regarding administration, he had a household of servants to take care of chores such as providing food. The household was run by a chamberlain, while a treasurer took care of the estate's written records. Royal households took essentially the same form as baronial households, although on a much larger scale and the positions were more prestigious. Without the presence of a lord's household, usually because he was staying elsewhere, a castle would have been a quiet place with few residents, focused on maintaining the castle. Not just a utilitarian structure, as social centres castles were also important places for display. Builders took the opportunity to draw on symbolism to evoke a sense of chivalry that was aspired to in the Middle Ages amongst the elite. Castles have been compared with cathedrals as objects of architectural pride, and some castles incorporated gardens as ornamental features. The right to crenelate, when granted by a monarch – though it was not always necessary – was important not just as it allowed a lord to defend his property but because crenelations and other accoutrements associated with castles were prestigious through their use by the elite.

The purpose of marriage between the medieval elites was to secure land, not for love; girls were married in their teens, but boys did not marry until they came of age. There is a popular conception that women played a peripheral role in the medieval castle household, and that it was dominated by the lord himself. This derives from the image of the castle as a martial institution, but most castles in England, France, Ireland, and Scotland were never involved in conflicts or sieges, so the domestic life is a neglected facet. The lady was given a "marriage portion" of her husband's estates – usually about a third – which were hers for life, and her husband would inherit on her death; it was her duty to administer them directly, as the lord administered his own land. Despite generally being excluded from military service, a woman could be in charge of a castle, either on behalf of her lordly husband or if she was widowed. Because of their influence within the medieval household women influenced construction and design, sometimes through direct patronage; historian Charles Coulson emphasises the role of women in applying "a refined aristocratic taste" to castles due to their long term residence. Courtly love was the eroticisation of love between the nobility. Emphasis was placed on restraint between lovers. It was sometimes in private and was expressed through chivalric events such as tournaments. The legend of Tristan and Iseult is one example of stories of courtly love told in the Middle Ages. It was an ideal of love between two people not married to each other, although the man might be married to someone else. It was not uncommon or ignoble for a lord to be adulterous – Henry I of England had over 20 bastards for instance – but for a lady to be promiscuous was seen as dishonourable.

Castle landscapes

As castles were not simply military buildings but centres of administration and symbols of power, they had a significant impact on the landscape around them. Rural castles were often associated with mills and field systems due to their role in managing the lord's estate, which gave them greater influence over resources. Others were adjacent to or in royal forests or deer parks and were important in their maintenance. Fish ponds were a luxury of the lordly elite, and many were found next to castles. Not only were they practical in that they ensured a water supply and fresh fish, but they were a status symbol as they were expensive to build and maintain.

Although sometimes the construction of a castle led to the destruction of a village, such as at Eaton Socon in England, it is more common for the villages nearby to have grown as a result of the presence of a castle. Sometimes planned towns or villages were created around a castle. The benefits of castle building on settlements was not confined to Europe; when Safad Castle was founded in Galilee, in the Holy Land, during the 13th century, the nearby town benefited from its presence as people could now move freely in the area and the 260 villages locally became profitable. When built, a castle could result in the restructuring of the local landscape, with roads moved for the convenience of the lord. Settlements grew naturally around a castle, rather than being planned, due to the benefits of proximity to an economic centre in a rural landscape and the safety given by the defences. Not all such settlements survived, as once the castle lost its importance – perhaps succeeded by a manor house as the centre of administration – the benefits of living next to a castle vanished and the settlement depopulated.

During and shortly after the Norman Conquest of England, castles were inserted into important pre-existing towns to control and subdue the populace. They were usually location with reference to any existing town defences, such as Roman walls, although this sometimes resulted in the demolition of structures occupying the desired site. In Lincoln, 166 houses were destroyed to clear space for the castle, and in York agricultural land was flooded to create a moat for the castle. As the military importance of urban castles waned from their early origins, they became more important as centres of administration, and their financial and judicial roles. When the Normans invaded Ireland, Scotland, and Wales in the 11th and 12th centuries, settlement in those countries was predominantly non-urban, and the foundation of towns is often linked with the creation of a castle.

Symbolism in relation to castles and their setting was very important, as demonstrated by the proximity of high status features such as fish ponds. Also often found near to a castle, sometimes within its defences, was the parish church. This has been interpreted as a relationship between the church and feudal lords, where the lords patronised the church, which was one of the most important institutions of medieval society. Even elements of castle architecture that have usually been interpreted as military can be highly symbolic. The water features of Kenilworth Castle in England – comprising a moat and several satellite ponds – forced anyone approaching the castle entrance to take a very indirect route, walking around the defences before the final approach towards the gateway. Another example is that of the 14th-century Bodiam Castle, also in England; although it appears to be a state of the art, advance castle it is in a site of little strategic importance, and the moat was shallow and more likely intended to make the site look more impressive than as a defence against mining. The approach was long and took the viewer around the castle, ensuring they got a good look before entering. Moreover, the gunports were impractical and unlikely to have been effective. This also demonstrates that licenses to crenellate were not solely about a desire to defend oneself, but to have proof of a relationship with or favour from the monarch, who was the one responsible for granting permission.

Warfare

A trebuchet at Château des Baux in France

As a static structure, castles could often be avoided as their immediate area of influence was about and their weapons had a short range even early in the age of artillery. However, leaving an enemy behind the army would allow them to interfere with communications and make raids in the landscape to harry the army. Garrisons were expensive and as a result often small unless the castle was important. In peace time garrisons were smaller due to the cost of upkeep, and small castles were manned by perhaps a couple of watchmen and gate-guards. Even in war garrisons were not necessarily large as too large a defending force would impair the castles ability to withstand a long siege; in 1403 a force of 37 archers successfully defended Caernarfon Castle against two assaults by Owain Glyndŵr's allies during a long siege. Early on, manning a castle was a feudal duty of vassals to their magnates, and magnates to their kings, however this was later replaced with paid forces. If it was necessary to control the castle for strategic reasons, an army could lay siege to it and starve the defenders out. Without relief from an outside source, the defending army would eventually submit, but sieges could last weeks, months, and in rare cases years if the supplies of food and water were plentiful. A long siege could slow down the army, allowing help to come or for the enemy to prepare a larger force for later. For the most heavily fortified sites it was more efficient to starve the garrison out that to assault it. Such an approach was not confined to castles, but was also applied to the fortified towns of the day. On occasion, siege castles would be built to defend the besiegers from a sudden sally.

If forced to assault a castle, there were many options available to the attackers. For wooden structures, such as early motte-and-baileys, fire was a real threat and attempts would be made to set them on fire. Project weapons had been used since antiquity and the mangonel and petraria – from Roman and Oriental origins respectively – were the main two that were used into the Middle Ages. The trebuchet, probably evolved from the petraria in the 13th century, was the most effective siege weapon before the development of cannons. These weapons were vulnerable to fire from the castle as they had a short range and were large machines. Conversely, weapons such as trebuchets could be fired from within the castle due to the high trajectory of its projectile, and would be protected from direct fire by the curtain walls. Eventually cannons developed to the point where they were more powerful and had a greater range than the trebuchet, and became the main weapon in siege warfare. Walls could be undermined by the creation of a sap; a mine would be dug to conceal the attackers approach to the wall, with wooden supports to prevent the tunnel from collapsing. When the target had been reached, the supports would be burned, caving in the tunnel and bringing down the structure above. Battering rams were also used, usually in the form of a tree trunk given an iron cap. They were used to batter down the castle gates, although they were sometimes used against walls, but with less effect. As an alternative to creating a breach in the walls, an escalade could be attempted to capture the walls, with fighting along the walkways on the curtain walls; in this instance, attackers would be very vulnerable to arrowfire, particularly from crossbows or the English longbow.

See also

• Alcázar (Spanish castles)

• Shiro (Japanese fortifications)