A castle is a defensive structure seen as one of the main symbols of the Middle Ages. The term has a history of scholarly debate surrounding its exact meaning, but it is usually regarded as being distinct from the general terms fort or fortress in that it describes a residence of a monarch or noble and commands a specific defensive territory.
Roman forts and hill forts were the main antecedents of castles in Europe, which emerged in the 9th century in Carolingian France. The advent of cannon and gunpowder changed the needs of warfare in Europe, limiting the effectiveness of the castle and leading to the rise of the fort.
A French castle is a Château-Fort, for in French a simple château connotes a grand country house at the heart of an estate, with non-military, purely residential function. When European castles were opened up and expanded into pleasure dwellings and power houses from the late 15th century, their "castle" designations, relics of the feudal age, often remained attached to the dwelling, resulting in many non-military castles and châteaux.
In Germany there are two names for what would be called a castle in English, Burg (Burh) and Schloss. A Burg is a medieval structure of military significance, while a Schloss was built after the Middle Ages as a palace and not for defensive purposes. However, these are not usually palaces in the French style, but instead are styled on medieval mountain castles and fairytale notions, and from all appearances are often castles to an English speaker.
In spite of the generally accepted definition, the word "castle" is sometimes used to mean a citadel (such as the castles of Badajoz and Burgos) or small detached forts d'arrêt in modern times and, traditionally, in Britain it has also been used to refer to prehistoric earthworks (e.g. Maiden Castle). The use of the Spanish equivalent castillo can be equally misleading, as it can refer to true castles and forts (eg. Castillo de San Marcos); terms such as Fortaleza ("fortress") are in similar situations.
The chief distinguishing features of castles, as opposed to other defensive structures, can be defined as follows:
These three purposes distinguish the castle from other fortresses — which are usually purely defensive (like citadels and city walls) or purely offensive (a military camp) — or edifices that are entirely residential in nature, like palaces. Castles such as the Tower of London served as prisons.
Castles were built as defensive measures and offensive weapons, but often over time comfortable homes evolved within the fortified walls. An example is the Windsor Castle, first built as a Norman Conquest fortress; today a home to the Queen of the United Kingdom. The Alhambra in Al-Andalus incorporated both defensive and residential features, but after the Reconquista unified Spain, its importance shifted and it became a palace under Charles V.
Construction of new castles in Europe is attested from the Carolingian era, but their construction seems to have been related mainly to the defence of frontiers and state properties, and the right to fortify was a royal privilege. As early as 864, Charles the Bald issued an edict ordering the destruction of private fortifications erected without his permission. However, changes took place from the late 9th century, probably under the pressure of raids by the Vikings and Magyars, and due to the general decline of the Carolingian Empire, and the consequent loss of centralized authority, which resulted in a proliferation of castles. There was also frequent fortification of cities, monasteries, ports and rural settlements in this period. In 906, a deacon in Verona asked Berengar I of Italy for permission to build a castle in Nogara "due to the heathens ravages".
As the Carolingian Empire broke up into duchies and counties, factions struggling for power created a military infrastructure, to protect their rights, their domains, and their followers. It is within this historical context that feudalism began to emerge. The early castle formed an integral part of feudalism: it provided a residence for the lord; provided protection for his followers as guaranteed by their feudal oaths of loyalty and allegiance, while the garrison of the castle was made up of the lord's followers, as per their feudal obligations. Many examples of defensive programs as part of feudalism exist. In the 10th century for example, in the Loire Valley, Fulk Nerra embarked on a massive castle-building program to control his county of Anjou, and neighbouring Touraine. In Normandy at around the same time, a military state emerged with a dense network of castles and feudal allegiances. Similar arrangements with regards to defensive and holding of territory also occurred in other parts of Europe around this time. .
Castles were introduced to the British Isles around the early 11th century, by Norman-French followers of King Edward the Confessor. When William the Conqueror executed the Norman Conquest of England, he brought with him the practice of building a castle to protect and hold the land, by then quite familiar on the mainland of Western Europe
The motte-and-bailey is a plan common to many early castles. An essential feature of this type was a circular mound of earth surrounded by a dry or water-filled ditch and flattened at the top. Around the crest of its summit was placed a timber palisade, a tower, possibly residential. This moated mound was styled in Old French motte (Latin mota), a word still common in French place-names. In addition to the mound, a bailey or basse court of horseshoe shape was usually appended to it, so that the mound stood on the line of the enceinte. The latter housed the domestic quarters, stables, stores, a forge and a water well. These earthworks were dug from the perimeter area, leaving a defensive ditch. In many cases the motte seems to be a later addition to an already existing wooden settlement, surrounded by a wood palisade. Lewes Castle, built by Gulielmus de Warenne, is an unusual example, as it featured two mottes. Wooden castles were built up until the 12th century.
A description of this earlier castle is given in the life of St John, Bishop of Terouanne:
The rich and the noble of that region being much given to feuds and bloodshed, fortify themselves ... and by these strongholds subdue their equals and oppress their inferiors. They heap up a mound as high as they are able, and dig round it as broad a ditch as they can ... Round the summit of the mound they construct a palisade of timber to act as a wall. Inside the palisade they erect a house, or rather a citadel, which looks down on the whole neighbourhood.
Castles were constructed of wood, stone and also brick. A large number of contemporary accounts have survived that explain how castles were built. A large skilled workforce was needed to construct castles, including ditch diggers, stonecutters, master masons such as Master James of St George, carpenters, and engineers. Medieval machines and inventions, such as the treadwheel crane, became indispensable during construction, and techniques of building wooden scaffolding were improved upon from Antiquity. Nevertheless, castles could take many years to complete, although the time needed depended greatly from type, location, resources, time period, construction materials, etc.
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 famous examples of some castles where stone was quarried on site, such as Chinon, Château de Coucy and Château Gaillard. Yet even without the usual costs of transport, it is estimated that as many as 800 stonemasons would have been used in building Château de Coucy in the early 13th century, as well as perhaps 800 other craftsmen. Beaumaris Castle in Wales, has surviving records from 1295–96 which describe 200 quarrymen, 400 stonemasons and as many as 2000 minor workmen. Castles, not surprisingly were expensive to build, considering workers and materials. For example, the costs for Beaumaris (which was part of a bigger castle program) were £14,500 (roughly $8–9 billion in today's money).
In some cases, transporting stone over large distances was altogether impractical, and in the Low countries, a lack of good building stone meant that castles were generally brick. Brick castles were predominant in Scandinavia and the Baltic.
During the Crusades, opportunities were afforded to western engineers to study the massive fortifications of the Byzantine Empire as well as fortifications built by the Islamic inhabitants of the Holy Land. The buildings they encountered in the late 10th century featured innovations which were not common in Europe at that time. This included in part regularly-spaced flanking towers of round or variable construction, and geometric scientific design. This revolutionized the art of castle-building in Europe, which henceforward followed these principles.
Designers soon realized that a second line of defences should be built within the main enceinte, and a third line or keep inside the second line, while a wall must be flanked by projecting towers. Thus from the Byzantine engineers, European castles derived the principle of mutual defence of all the parts of a fortress. The donjon of Western Europe was regarded as the fortress, the outer walls as accessory defences; in the East each envelope was a fortress in itself, and the keep became merely the last refuge of the garrison, used only when all else had been captured. Many scholars have noted that in the 13th century there was a tendency toward the strengthening of the enceinte, and a reduced role of the keep in both military and residential context.
In Richard I of England's fortress of Château-Gaillard Les Andelys, the innermost ward was protected by an elaborate system of strong appended defences, which included a strong tête-de-pont protecting the Seine bridge. The castle stood upon high ground and consisted of three distinct enceintes or wards besides the keep, which was in this case merely a strong tower forming part of the innermost ward. Frederick II's Castel del Monte in Puglia has no keep at all: built on high ground, it is an octagonal structure with eight polygonal corner towers.
Round towers, rather than square towers, were now becoming common, with the finest examples of their employment as keeps being at Conisborough in England and at Falaise and Coucy in France. Siege artillery of the 13th century was primitive, but it was realized that against mining and battering rams, corners in castle stonework were more vulnerable than a uniform curved surface.
The next development was the extension of the principle of successive lines of defence to form what is called the "concentric" castle, in which each ward was placed wholly within another which enveloped it. This was inspired by the Walls of Constantinople, and thus places built on a flat site became for the first time more formidable than strongholds perched upon rocks and hills, where some points could not be as heavily fortified as others for lack of space. In these cases, the fall of the inner ward by surprise, escalade, or even sometimes by ordinary siege, entailed the fall of the whole castle. The adoption of the concentric system precluded any such mischance, and thus, even though siege engines improved during the 13th and 14th centuries, the defences of strong concentric castle, or naturally inaccessible castles, retained its importance during the Late Middle Ages.
Construction of castles in this period was often connected to the necessity to establish a strong central power against local fragmentation, or in newly conquered lands: examples are the large building programs of Edward I of England in Wales, Philip I August of France, the Ezzelino IV da Romano and the Scaligers in northern Italy, Frederick II and Charles I of Anjou in southern Italy (often reusing former Norman or even Byzantine and Lombard structures), King Denis I in Portugal, and notably the Teutonic Knights in their conquest of Pagan lands in Prussia and Poland. In Germany, stone structures appeared in Hesse, Thuringia, Alsace and Saxony, commissioned by the powerful local aristocracy. Structures in northern Germany were usually simpler, often taking advantage of water streams.
Whilst siegecraft had consisted of throwing machines such as trebuchets, the primary aims in the construction of castle walls were height and thickness. However it became almost impossible to follow this ideal to cope with ever more powerful cannons. Existing castles which retained military importance were updated as far as practically possible to cope with new siege technologies. One example is the English fortress of Bodiam, built from 1385, provided with opposite slit to allow firing from arquebuses. But inevitably, those fortifications previously deemed impregnable eventually proved inadequate in the face of gunpowder. These included: Friesack Castle, which was reduced in two days during February of 1414 by Frederick I with "Heavy Peg" (Faule Grete) and other guns; Constantinople, the massively strong walls of which were breached in 1453 by the Ottomans after lengthy cannon bombardment; Nanstein Castle (Franz von Sickingen's stronghold at Landstuhl, which was ruined in one day in 1523 by the artillery of Philip of Hesse. Architects of the Late Middle Ages and Renaissance, many of whom were also renowned as engineers, were called to plan countermeasures; e.g. Guillén Sagrera, Giuliano da Sangallo the Younger, Francesco di Giorgio Martini, Baldassarre Peruzzi and Leonardo da Vinci. Viollet-le-Duc, in his Annals of a Fortress, gives a full account of the repeated renovations of a fortress (at an imaginary site in the valley of the Doubs), the construction by Charles the Bold of artillery towers at the angles of the castle, the protection of the masonry by earthen outworks, boulevards and demi-boulevards, and, in the 17th century, the final service of the medieval walls and towers as a pure enceinte de sfireti.
The general adoption of cannons led therefore to the disappearing (or to the loss of importance) of majestic towers and merlons. Walls of new fortresses were thicker and angulated, towers became lower and stouter. Examples of the late type of castle-fortress are that in Sarzana (Italy), that built by Henry VIII of England in Deal, the Fort de Salses constructed by Ferdinand II of Aragon and the Imperial Castle of Nurnberg.
In the end, the introduction of gunpowder led to a disappearing of traditional castles, in the meaning of a building intended for both military and residential roles. This transition began in the 14th century and was fully underway by the 15th. In the 16th century the feudal fastness had become an anachronism. Here and there we find old castles serving in secondary roles, as forts d'arret or block-houses in mountain passes and defiles, and in some few cases, as at Dover, they formed the nucleus of purely military places of arms. Normally castles, when they were not let to fell into ruins, became peaceful mansions, or were merged in the fortifications of the town which has grown up around it.
In the Viollet-le-Duc's Annals of a Fortress the site of the feudal castle is occupied by the citadel of the walled town, for once again, with the development of the middle class and of commerce and industry, the art of the engineer came to be displayed chiefly in the fortification of cities. The baronial "castle" assumes pan passu the form of a mansion, retaining indeed for long some capacity for defence, but in the end losing all military characteristics save a few which survived as ornaments.
However, some true castles were built in the Americas by the Spanish 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.
To guard against artillery and gunfire, increasing use was made of earthen, brick and stone breastworks and this redoubts, such as the geometric fortresses of the 17th century French Marquis de Vauban. These soon replaced castles in Europe, and eventually castles in the Americas were superseded by bastions and forts.
From the late 18th century to the early 20th century, as a manifestation of a romantic interest in the Medieval period, and as part of the broader Gothic Revival in architecture, many so-called castles were built. These castles had no defensive purpose, but incorporated stylistic elements of earlier castles, such as castellation and towers. The Scottish Baronial style personified these features. 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 was the last flicker of this movement in England. In Ireland, a considerable number of vast, complicated mock-castles were built, including Belfast Castle and Castle Oliver. Famous revival castles in other countries include Neuschwanstein in Germany, Miramare in Italy, and Castillo de Chapultepec in Mexico.
List of castles: