A castle is a type of fortified structure built in Europe and the Middle East during the Middle Ages by nobility. The word castle is often used to describe various types of fortifications with some common features or, in some languages, it has become a generic term for a manor house.
In scholarship, the castle is defined as a private fortified residence of a lord or noble. It is generally considered that castles originated in Europe in the 9th and 10th centuries and later spread to parts of the Middle East, where they were introduced by European Crusaders.
The word castle is derived from the Latin word castellum, which is a diminutive of the word castrum, meaning "fortified place". The word was introduced into English shortly before the Norman Conquest to denote this type of building, which was then new to England.
Usage of the term has varied over time and has been applied to various structures, such as fortresses, forts and even country houses. Moreover, in different areas of the world, analogous structures shared features of fortification and other defining characteristics associated with the concept of a castle.
Castles are considered a European innovation that dates from the 9th century. After the fall of the Carolingian Empire, a vast territory has been divided among individual lords and princes. These nobles built castles to control the area immediately surrounding them, and were both offensive and defensive structures: they provided a base from which raids could be launched as well as protection from enemies.
The structures also served as centres of administration and symbols of power and they were often located near important features, such as main roads, mills and fertile land.
At the beginning, most castles were built from earth and timber, but had their defences replaced later by stone. Early castles often exploited natural defences, lacking features such as towers and arrowslits and relying only on a central keep (or main tower).
In the late 12th century, a scientific approach to castle defence emerged. Many changes in castle technology were a direct result of the Crusades, although some inspiration came from earlier defences, such as Roman forts. Many new castles were polygonal or relied on concentric defence – several stages of defence within each other that could all function at the same time to maximise the castle's firepower.
Another important change was the proliferation of towers, which would greatly improve the castle's defence and fire power. Moats were built to surround the castle and provide a preliminary line of defence.
Gunpowder was introduced to Europe in the 14th century and by the end of the 15th century, artillery became powerful enough to break through stone walls. Castles continued to be built into the 16th century, until new techniques to deal with improved cannon fire made them uncomfortable and undesirable places to live. As a result, true castles went into decline, and were replaced by artillery forts with no role in civil administration.
Towards the end of the Middle Ages, castles became more important as residences and statements of power. Over time, the aesthetics of the design became more important, as castle appearance and size began to reflect the prestige and power of its occupant. Castles still provided protection from low levels of violence, but they were mainly used as comfortable homes where lords or knights could entertain their companions.
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 military purpose.
Here is a great animation showing how castle designs evolved over time:
Although, over the approximately 900 years that castles were built, they took on a great many forms with many different features, some of them were commonplace.
The motte was an earthen mound with a flat top. It was often artificial, although sometimes it incorporated a pre-existing feature of the landscape. The excavation of earth to make the mound left a ditch around the motte, called a moat which could be either wet or dry.
Motte -- Chateau de Gisors, France
In many cases, the "motte" and "moat" evolved from their original purpose of defence into symbols of power. Some grand castles had long winding approaches intended to impress and dominate their landscape.
A bailey, also called a ward, was a fortified enclosure. 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 were often found in the bailey.
Krak des Chevaliers Castle: fortified enclosure
Over time, the focus of high status accommodation shifted from the keep to the bailey; this 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.
The Keep was traditionally the heart of any Medieval castle. It was the tallest and strongest tower and usually the most strongly defended point of a castle. In early Medieval times, the keep was used as a residence by the lord who owned the castle, or his guests or representatives.
Keep at Chateau de Vincennes, France
In later Medieval times, as castles began to change into grand residential buildings, the nobles began to live in warmer, comfier chambers and the keep became a strong-hold. Sometimes, the keep was used as a prison.
Keep was not a term used in the medieval period; instead donjon was used to refer to great towers (do not confuse with dungeon which is a completely different thing).
Curtain walls were defensive walls enclosing the 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 gunpowder artillery.
A typical wall could be 3 m (10 ft) thick and 12 m (39 ft) tall, although sizes varied greatly between castles. Walkways along the tops of the curtain walls allowed defenders to rain missiles on enemies below, and battlements gave them further protection.
Arrowslits were thin vertical apertures in fortification walls through which archers could launch arrows. They become common in Europe from the 13th century.
Drawing of battlements and arrowslits on a castle tower
From the late 12th century, many castles built additional towers for defence purposes. The towers provide vantage-points for archers to shoot at oncoming attackers. As time went on, the design and construction of different towers became grander and more ambitious.
The towers of Caernarfon Castle, Wales
The entrance has beeen often the weakest part in the circuit of defences; people and supplies needed access to the castle, but building a route into the castle created an obvious route for attackers.
Castle designers had to come with a solution to make a direct assault more difficult than battering down a simple gate. The gatehouse was a fortified entrance, with numerous different doors and portcullises, tricks and obstacles, all used to guard the castle.
a portcullis is a wooden grille reinforced with metal used to block a passage
Projecting towers were added on each side of the gate and arrowslits were put to allow defenders to harry the enemy. The passage through the gatehouse was lengthened to increase the amount of time an assailant had to spend under fire in a confined space and unable to retaliate.
13th century gatehouse in the Castle of Chateaubriant, France
Some castles had two different gatehouses - one on the outer-castle, and one on the inner, just in case the outer one was breached.
A moat was a defensive ditch with steep sides, and could be either dry or filled with water. Its purpose was to stop devices such as siege towers from reaching the curtain wall and to prevent the walls from being undermined.
Caerlaverock Castle in Scotland, surrounded by a moat
Water moats were found in low-lying areas and were usually crossed by a drawbridge. In some places moats evolved into more extensive water defences, including natural or artificial lakes. Water defences had the benefit of dictating the enemy's approach to the castle.
Castles in other parts of the world
Japanese castles (shiro) were fortresses constructed primarily of wood and stone. They evolved from the wooden stockades of earlier centuries, and came into their best-known form in the 16th century. Castles in Japan were built to guard important or strategic sites, such as ports, river crossings, or crossroads, and almost always incorporated the landscape into their defenses.
Japanese castles were constructed primarily of wood, and many were destroyed over the years. However, many were rebuilt, some as national heritage sites or museums. Today there are more than one hundred castles extant, or partially extant, in Japan; it is estimated that once there were five thousand.
Most castles in Nord America (especially USA and Canada) cannot be described as true castles. They are primarily country houses, follies, or other types of buildings built to give the appearance of a castle.
European-style fortifications, castles and outposts (mostly Portuguese, Dutch and British) were built in various parts of the world during the colonial period. These include countries like India, Ghana, Sri Lanka, South Africa and others.