Editing Concentric castle (section)

== Development ==
[[File: Grondplan citadel Lille.JPG|thumb|Star-shaped plan of the citadel of [[Lille]] (France), designed by Vauban]]
[[File:Beaumaris plan, Cadw.jpg|thumb|right|Plan of [[Beaumaris Castle]] (Wales)]]
Surrounding fortresses or towns with a series of [[defensive wall]]s where the outer walls are lower than the inner walls is something that has been found in fortifications going back thousands of years to cultures like the [[Assyrian people|Assyrians]], [[Persian people|Persians]], [[Ancient Egyptians]] and [[Babylonians]]. The ancient city of [[Lachish]], a place in [[Israel]], was excavated and found to consist of multiple walls that were illustrated in Assyrian art documenting their successful siege of the city. The Byzantines also famously constructed the [[Walls of Constantinople]], which featured double layers of walls through most of its perimeter and a [[moat]]. The city of ancient Babylon also featured multiple layers of [[fortifications]], famously seen in the [[Ishtar Gate]]. However, the relationship of the concentric castle to other forms of fortification is complex. An example of an early concentric castle is the Byzantine castle of [[Corycus|Korykos]] in Turkey, built in the early 11th century AD.<ref>{{Cite book|title=Byzantine fortifications an introduction|first=Clive|last=Foss|date=1986|publisher=Univ. of South Africa|isbn=0869813218|oclc=254999395}}</ref> 

Historians (in particular [[Hugh N. Kennedy|Hugh Kennedy]]) have argued that the concentric defence arose as a response to advances in [[siege]] technology in the [[crusader state]]s from the 12th to the 13th century. The outer wall protected the inner one from [[siege engine]]s, while the inner wall and the projecting towers provided flanking fire from [[crossbows]]. Also, the strong towers may have served as platforms for [[trebuchet]]s for shooting back at the besiegers. The walls typically include [[tower]]s, [[arrowslit]]s, and wall-head defences such as [[crenellation]] and, in more advanced cases, [[machicolation]]s, all aimed at an active style of defence.<ref name=kennedy2000 /> The [[Krak des Chevaliers]] in [[Syria]] is the best-preserved of the concentric crusader castles. By contrast, [[Château Pèlerin]] was ''not'' a concentric castle, as the side facing the sea did not require defensive walls. However, the two walls facing the land are built on the same defensive principles as other crusader castles in the same period, rivalling the defences at Krak.

While a concentric castle has double walls and towers on all sides, the defences need not be uniform in all directions. There can still be a concentration of defences at a vulnerable point. At Krak des Chevaliers, this is the case at the southern side, where the terrain permits an attacker to deploy siege engines. Also, the gate and [[postern]]s are typically strengthened using a [[bent entrance]] or flanking towers.

Concentric castles were expensive to build, so that only the powerful military orders, the [[Knights Hospitaller|Hospitallers]] and [[Templars]], or powerful kings could afford to build and maintain them. It has also been pointed out that the concentric layout suited the requirements of military orders such as the Hospitallers in resembling a [[monastery]] and housing a large garrison. Such castles were beyond the means of feudal barons. Thus, concentric castles coexisted with simpler enclosure castles and tower [[keep]]s even in the [[crusader state]]s.<ref name="nicolle2008">{{cite book|title=Crusader Castles in the Holy Land: An Illustrated History of the Crusader Fortifications of the Middle East and Mediterranean|author=Nicolle, David|year=2008|ISBN=978-1846033490}}</ref>

Concentric castles appeared in [[Europe]] in the 13th century, with the castles built in [[Wales]] by [[Edward I of England|Edward I]] providing some outstanding examples, in particular [[Beaumaris Castle]], a "perfect concentric castle",<ref name=brown1989>{{cite book | author = Reginald Allen Brown | title = Castles from the air | publisher = Cambridge University Press | year = 1989 | ISBN = 978-0-521-32932-3 }}</ref> albeit unfinished. As Beaumaris was built on flat terrain rather than a [[Spur (topography)|spur]], it was both necessary and possible to build walls and towers facing in all directions, giving a very regular, almost square, floor plan to the castle. Some influence from crusader fortification has been conjectured, but the amount of technology transfer from the East and much earlier Byzantine examples remains controversial among historians.<ref name=kennedy2000 />