Medieval fortification refers to military methods that cover the development of fortification construction and use in Europe, during the period roughly from the fall of the Western Roman Empire until the Renaissance. During this millennium, fortifications changed warfare and in turn were modified to suit new tactics, weapons, and siege techniques.
Fortification types
Castles
The castle, defined by historian John Goodall as "the residence of a lord made imposing through the architectural trappings of fortification," was the archetypal medieval fortification. The combination of private elite residences with serious fortifications was not seen in European history outside the Middle Ages, and was inextricably linked to the feudal system.Goodall 2011, p. 50 The castle developed in France around 900 AD, in the instability that followed the collapse of the Carolingian Empire, when lords wished to defend their own interests rather than relying on the state. Early earth-and-timber forms, such as the motte-and-bailey and ringwork, were superseded by more imposing and durable stone structures. Early stone castles generally had a central keep, or great tower, but in the later 12th century the defensive focus generally moved to the curtain wall, finding its ultimate expression in the concentric castles of the later 13th century.
Other fortified houses
Where financial limitations or the lack of serious military threats made the construction of a castle impossible or unnecessary, lesser lords and members of the gentry built other forms of fortified house. In more settled areas, a fortified manor house, such as may be seen in England from the later 13th century, gave the builder some protection and the status benefits of a castle without sacrificing domestic comfort. Fortified manor houses could also result from a previously peaceful area with unfortified houses descending into war. This happened at the Scottish border after the start of the Wars of Scottish Independence in 1296, when manors like Aydon Castle were hurriedly made defensible by adding curtain walls and blocking windows. Tower houses were a common response to living in unsettled areas like Scotland and Ireland, forming an imposing, secure and spatially efficient dwelling. The height of tower houses could be a source of competition, especially in urban areas, resulting in the fantastical skylines of towns like San Gimignano. When a tower house was too expensive, the inhabitant could build a smaller structure like a peel tower or even a bastle house, the latter little more than a sturdily-built farmhouse.
City walls
Cities were generally walled, even where there was no military threat, as a status symbol and to enable toll collection. Many cities, such as London, retained their Roman fortifications, which were repaired and extended in the Middle Ages. Where Roman fortifications were not available, early construction was generally in earth and timber, usually later replaced with stone. This would have been the pattern of events in the Five Boroughs of the Danelaw in England. Fortified towns, or bastides, were used to support colonisation by the English and French, namely Edward I's annexation of north Wales and the French campaign against the Cathars in the Languedoc, forming the basis of settlement in hostile territory.
In many cases, the wall would have had an internal and an external pomoerium. This was a strip of clear ground immediately adjacent the wall. The word is from the late medieval, derived from the classical Latin post murum ("behind the wall"). An external pomoerium, stripped of bushes and building, gave defenders a clear view of what was happening outside and an unobstructed field of shot. An internal pomoerium gave ready access to the rear of the curtain wall to facilitate movement of the garrison to a point of need. By the end of the sixteenth century, the word had developed further in common use, into pomery.
Bridges
Bridges, particularly leading into towns, were often fortified with towers straddling the roadway. As these were an impediment to traffic, few have survived to the present, though the bridges that carried the towers often have, as at Durham. Occasionally the bridgehead was further defended with a tower or fort, as at Córdoba.
Harbours
Harbours or some sort of water access were often essential to the construction of medieval fortifications. Having direct access to a body of water provided a route for resupply in times of war, and an additional method of transportation in times of peace. The concept of rivers or harbours coming directly up to the walls of fortifications was especially used by the English as they constructed castles throughout Wales, with both Conwy and Beaumaris having defended docks, while at Rhuddlan the River Clwyd was canalised for three miles to allow ships to reach the castle. There is evidence that harbours were fortified, with wooden structures in the water creating a semi-circle around the harbour, or jetties, as seen in an artist's reconstruction of Hedeby, in Denmark, with an opening for ships to access the land. Shipyards could also be fortified, as at the Venice Arsenale and the Barcelona Royal Shipyard.
Churches and monasteries
In some regions, churches and monasteries were fortified, either by enclosure within a curtain wall, or by fortification of the church itself. Examples of the former include the fortified churches of Transylvania and the fortified monasteries of Russia (such as Solovetsky), while the latter can be impressively seen in the fortified brick churches built in southern France after the Albigensian Crusade, such as Albi Cathedral. Many of the Crusader castles were built by orders of fighting monks, such as the Templars, Hospitallers and Teutonic Knights, and had all the buildings of a normal monastery, like a chapter house and refectory, within their walls.
Watchtowers
Some cities and castles on frontiers had outlying networks of small forts and watchtowers, by which enemy movements could be relayed and their progress towards the main fortress impeded. The Moorish Kingdom of Granada had such a system of towers around Malaga. Richard I's great castle of Château Gaillard similarly had two advance fortifications - the tower of Boutavant on the River Seine and the small castle of Cléry.Snow 2012, p. 111
Temporary fortifications
Medieval siege warfare relied on the effective isolation of the besieged fortification to prevent resupply, especially before the development of more powerful siege engines in the 12th century. This often required the construction of temporary fortifications, from simple pavise shields to large earth and timber siege castles that could be used for years. An example is The Rings at Corfe, a substantial ringwork that opposed Corfe Castle during the Anarchy. Where a conflict was long but stagnant, counter castles could become full castles in their own right, as at Roumelihissar (1451-52), built to cut off shipping into Constantinople. Siegeworks also included earthen platforms to mount siege engines, and later cannon; the earth "buttresses" around Berkhamsted Castle may have been such platforms to carry French engines in the siege of 1216. Defenders could also erect their own temporary works, if a siege was anticipated. Before the development of machicolations, many walls and towers had putlog holes at the wallheads, in which beams to carry timber hoardings could be inserted. Similarly, Dover Castle had a timber barbican outside the north gate, which may have been built shortly before the 1216 siege.Snow 2012, p. 59
Defensive obstacles Medieval engineers used a number of obstacle types including abatis, caltrops, cheval de frise, and trou de loup.
Siege warfare
Sieges were common during the Middle Ages and because of this many cities fortified their walls and castles to defend against the use of siege engines by their attackers1. Many cities utilized catapults that would hurl stones and other missiles at enemy siege engines and soldiers. The most commonly used catapult for defense was the trebuchet, a torsion powered catapult that dominated the Middle Ages both offensively and defensively. The trebuchet was known for its considerable force but required a longer loading time compared to other siege engines, sometimes taking up to an hour, which lead to some cities using catapults such as the mangonel and onager instead, which could put projectiles downrange much faster than the trebuchet. The trebuchet’s destructive force caused engineers to thicken walls, round out towers, and to redesign fortifications so that they could employ trebuchets for defense. The Ayyubids between 1196 and 1218 built towers mounted with massive trebuchets, which hypothetically would use their height advantage to take out opposing siege engines. Ballistas were another type of catapult utilized as a defensive weapon, however they were not often used. This is because their missiles sometimes lacked the force to dismantle enemy siege engines and their immobility confined them to the top of a city's towers were they could easily be taken out by enemy catapults, including offensive ballistas which were usually employed for the very reason of dismantling defenses on the top of towers and keeping defenders off of a wall's battlements. After the invention of cannons near the beginning of 12th century CE, many torsion powered catapults became largely obsolete and cannons became commonplace medieval siege engines by the 15th century. While mostly used for offensive purposes, the first recorded use of a cannon in Europe was to defend the city of Algeciras during the siege of 1343-44. However slow to load, cannons proved to be devastating weapons that could level a city's walls or destroy siege engines with only a single projectile.
Construction
Construction could sometimes take decades. The string of Welsh castles Edward I of England had built were an exception in that he focused much of the resources of his kingdom on their speedy construction. In addition to paid workers, forced levies of labourers put thousands of men on each site and shortened construction to a few years.
Location
Nature could provide very effective defences for the castle. For this reason many castles were built on larger hills, cliffs, close to rivers, lakes or even caves.
Materials Materials that were used in the building of castles varied through history. Wood was used for most castles until 1066. They were cheap and were quick to construct. The reason wood fell into disuse as a material is that it is quite flammable. Soon stone became more popular.
Stone castles took years to construct depending on the overall size of the castle. Stone was stronger and of course much more expensive than wood. Most stone had to be quarried miles away, and then brought to the building site. But with the invention of the cannon and gunpowder, castles soon lost their power.
Costs
Costs for the walls depended on the material used. Wood would cost very little and was quick to build, but was weak. Stone was strong but very expensive and time-consuming to construct.
Manpower Work was done by teams of craftsmen assisted by local labour. For larger projects, skilled labour would often be brought in from surrounding areas.Speculum, Vol. 39 No. 3 July 1964
Features
Walls
The height of walls varied widely by castle, but were often thick. They were usually topped with crenellation or parapets that offered protection to defenders. Some also featured machicolations (from the French machicoulis, approximately "neck-crusher") which consisted of openings between a wall and a parapet, formed by corbelling out the latter, allowing defenders to throw stones, boiling water, and so forth, upon assailants below. Some castles featured additional inner walls, as additional fortifications from which to mount a defence if outer walls were breached.
Gates