thumb|upright=1.3|Reconstruction of the English city of [[York in the 15th century, showing the motte and bailey of York Castle on the right and another motte (Baile Hill) in the left foreground]]
thumb|Diagram of motte-and-bailey style layout
A motte-and-bailey castle is a European fortification with a wooden or stone keep situated on a raised area of ground called a motte, accompanied by a walled courtyard, or bailey, surrounded by a protective ditch and palisade. Relatively easy to build with unskilled labour, but still militarily formidable, these castles were built across northern Europe from the 10th century onwards, spreading from Normandy and Anjou in France, into the Holy Roman Empire, as well as the Low Countries it controlled, in the 11th century, when these castles were popularized in the area that became the Netherlands. The Normans introduced the design into England and Wales. Motte-and-bailey castles were adopted in Scotland, Ireland, and Denmark in the 12th and 13th centuries. By the end of the 13th century, the design was largely superseded by alternative forms of fortification, but the earthworks remain a prominent feature in many countries.
Architecture
Structures
thumb|Plan of [[Topcliffe, North Yorkshire|Topcliffe Castle in North Yorkshire, England, an archetypal motte-and-bailey design]]
thumb|[[Church Pulverbatch|Castle Pulverbatch in Shropshire, England, was built in the 11th or 12th century and abandoned by 1202. This digital elevation model shows the motte just left of centre, with the bailey to the right (north-east) of it.]]
A motte-and-bailey castle was made up of two structures: a motte (a type of mound – often artificial – topped with a wooden or stone structure known as a keep); and at least one bailey (a fortified enclosure built next to the motte). The constructive elements themselves are ancient, but the term motte-and-bailey is a relatively modern one and is not medieval in origin. The word is the French version of the Latin , and in France, the word , generally used for a clump of turf, came to refer to a turf bank, and by the 12th century was used to refer to the castle design itself. The word "bailey" comes from the Norman-French , or , referring to a low yard. In medieval sources, the Latin term was used to describe the bailey complex within these castles.
One contemporary account of these structures comes from Jean de Colmieu around 1130, describing the Calais region in northern France. De Colmieu described how the nobles would build "a mound of earth as high as they can and dig a ditch about it as wide and deep as possible. The space on top of the mound is enclosed by a palisade of very strong hewn logs, strengthened at intervals by as many towers as their means can provide. Inside the enclosure is a citadel, or keep, which commands the whole circuit of the defences. The entrance to the fortress is by means of a bridge, which, rising from the outer side of the moat and supported on posts as it ascends, reaches to the top of the mound". At Durham Castle, contemporaries described how the motte-and-bailey superstructure arose from the "tumulus of rising earth" with a keep rising "into thin air, strong within and without" with a "stalwart house ... glittering with beauty in every part".
Motte
thumb|The motte and bailey defences of [[Launceston Castle in Cornwall, England]]
Mottes were made out of earth and flattened on top, and it can be very hard to determine whether a mound is artificial or natural without excavation. Some were also built over older artificial structures, such as Bronze Age barrows. The size of mottes varied considerably, with these mounds being 3 metres to 30 metres in height (10–100 feet), and from in diameter. This minimum height of for mottes is usually intended to exclude smaller mounds which often had non-military purposes. In England and Wales, only 7% of mottes were taller than high; 24% were between , and 69% were less than tall. A motte was protected by a ditch around it, which would typically have also been a source of the earth and soil for constructing the mound itself.
A keep and a protective wall would usually be built on top of the motte. Some walls would be large enough to have a wall-walk around them, and the outer walls of the motte and the wall-walk could be strengthened by filling in the gap between the wooden walls with earth and stones, allowing it to carry more weight; this was called a garillum. Smaller mottes could support only simple towers with room for a few soldiers, whilst larger mottes could be equipped with a much grander building. Many wooden keeps were designed with bretèches, or brattices, small balconies that projected from the upper floors of the building, allowing defenders to cover the base of the fortification wall. The early 12th-century chronicler Lambert of Ardres described the wooden keep on top of the motte at the castle of Ardres, where the "first storey was on the surface of the ground, where were cellars and granaries, and great boxes, tuns, casks, and other domestic utensils. In the storey above were the dwelling and common living rooms of the residents in which were the larders, the rooms of the bakers and butlers, and the great chamber in which the lord and his wife slept ... In the upper storey of the house were garret rooms ... In this storey also the watchmen and the servants appointed to keep the house took their sleep". Wooden structures on mottes could be protected by skins and hides to prevent their being easily set alight during a siege. The bailey was often kidney-shaped to fit against a circular motte but could be made in other shapes according to the terrain. The bailey was connected to the motte by a bridge, or, as often present in England, by steps cut into the motte. Typically the ditch of the motte and the bailey joined, forming a figure of eight around the castle. Wherever possible, nearby streams and rivers would be dammed or diverted, creating water-filled moats, artificial lakes and other forms of water defences.
In practice, there was a wide number of variations to this common design. A castle could have more than one bailey: at Warkworth Castle an inner and an outer bailey were constructed, or alternatively, several baileys could flank the motte, as at Windsor Castle. Some baileys had two mottes, such as those at Lincoln. Instead of single ditches, occasionally double-ditch defences were built, as seen at Berkhamsted.
Construction and maintenance
thumb|Building the motte of [[Hastings Castle (HESTENGA CEASTRA) in East Sussex, from the Bayeux Tapestry]]
Various methods were used to build mottes. Where a natural hill could be used, scarping could produce a motte without the need to create an artificial mound, but more commonly much of the motte would have to be constructed by hand.
Regardless of the sequencing, artificial mottes had to be built by piling up earth; this work was undertaken by hand, using wooden shovels and hand-barrows, possibly with picks as well in the later periods. Larger mottes took disproportionately more effort to build than their smaller equivalents, because of the volumes of earth involved. Contemporary accounts talk of some mottes being built in a matter of days, although these low figures have led to suggestions by historians that either these figures were an underestimate, or that they refer to the construction of a smaller design than that later seen on the sites concerned. Taking into account estimates of the likely available manpower during the period, historians estimate that the larger mottes might have taken between four and nine months to build. This contrasted favourably with stone keeps of the period, which typically took up to ten years to build. Very little skilled labour was required to build motte and bailey castles, which made them very attractive propositions if forced peasant labour was available, as was the case after the Norman invasion of England.
thumb|A cross-section showing the layers within the motte at [[York Castle|Clifford's Tower in York: "A" marks the 20th-century concrete underpinnings of the motte; the low walls enclosing the base of the motte are a 19th-century addition.]]
The type of soil would make a difference to the design of the motte, as clay soils could support a steeper motte, whilst sandier soils meant that a motte would need a more gentle incline. Layers of turf could also be added to stabilise the motte as it was built up, or a core of stones placed as the heart of the structure to provide strength. Similar issues applied to the defensive ditches, where designers found that the wider the ditch was dug, the deeper and steeper the sides of the scarp could be, making it more defensive. Soil wash was a problem, particularly with steeper mounds, and mottes could be clad with wood or stone slabs to protect them.
Although motte-and-bailey castles are the best-known castle design, they were not always the most numerous in any given area. A popular alternative was the ringwork castle, involving a palisade being built on top of a raised earth rampart, protected by a ditch. The choice of motte and bailey or ringwork was partially driven by terrain, as mottes were typically built on low ground, and on deeper clay and alluvial soils. Another factor may have been speed, as ringworks were faster to build than mottes. Some ringwork castles were later converted into motte-and-bailey designs, by filling in the centre of the ringwork to produce a flat-topped motte. The reasons for why this decision was taken are unclear; motte-and-bailey castles may have been felt to be more prestigious, or easier to defend; another theory is that like the terpen in the Netherlands, or Vorburg and Hauptburg in Lower Rhineland, raising the height of the castle was done to create a drier site. European castles first emerged between the Loire river and the Rhine in the 9th and 10th centuries, after the fall of the Carolingian Empire resulted in its territory being divided among individual lords and princes and local territories became threatened by the Magyars and the Norse. Against this background, various explanations have been put forward to explain the origins and spread of the motte-and-bailey design across western and northern Europe; there is often a tension among the academic community between explanations that stress military and social reasons for the rise of this design. One suggestion is that these castles were built particularly in order to protect against external attack – the Angevins, it is argued, began to build them to protect against the Viking raids, and the design spread to deal with the attacks along the Slav and Hungarian frontiers. Another argument is that, given the links between this style of castle and the Norman style, who were of Viking descent, it was in fact originally a Viking design, transported to Normandy and Anjou. The motte-and-bailey castle was certainly effective against assault, although as historian André Debord suggests, the historical and archaeological record of the military operation of motte-and-bailey castles remains relatively limited.
An alternative approach focuses on the links between this form of castle and what can be termed a feudal mode of society. The spread of motte-and-bailey castles was usually closely tied to the creation of local fiefdoms and feudal landowners, and areas without this method of governance rarely built these castles. Yet another theory suggests that the design emerged as a result of the pressures of space on ringworks and that the earliest motte-and-baileys were converted ringworks.