Editing Defensive wall (section)

{{short description|Fortification used to protect an area from potential aggressors}}
{{Redirect-distinguish|City wall|Border barrier}}
{{For-multi|the expression used in association football|Glossary of association football terms#W|the infantry formation|Shield wall}}

{{multiple image|perrow = 3|total_width=400
| image1 = Walls of Constantinople.JPG
| image2 = Hadrian's wall at Greenhead Lough.jpg
| image3 = Avila - Murallas, Paseo de la Ronda Vieja 05.JPG
| image4 = Pingyao-muralla-c01-f.jpg
| image5 = Nanjing Ming wall.jpg
| image6 =  20090529 Great Wall 8125.jpg
| image7 =  Walls of Dubrovnik-3.jpg
| image8 =  Al-wastani gate.jpg
| image9 =  Jaisalmer citadelle.jpg
| footer = Left to right: [[Walls of Constantinople]], [[Hadrian's Wall]], [[Walls of Ávila]], walls of [[Pingyao]] and [[Nanjing]], two sections of the [[Great Wall of China]], [[Walls of Dubrovnik]], [[Gates of Baghdad]], walls of the [[Jaisalmer Fort]].
}}
A '''defensive wall''' is a [[fortification]] usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple [[palisade]]s or [[Earthworks (military)|earthwork]]s to extensive military fortifications such as [[curtain wall (fortification)|curtain wall]]s with [[Fortified tower|tower]]s, [[bastion]]s and [[gate]]s for access to the city.<ref>{{Cite book|title=Encyclopedia of the City|last=Caves|first=R. W.|publisher=Routledge|year=2004|isbn=978-0415862875|pages=756}}</ref> From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as '''city walls''' or '''town walls''', although there were also walls, such as the [[Great Wall of China]], [[Walls of Benin]], [[Hadrian's Wall]], [[Anastasian Wall]], and the [[Atlantic Wall]], which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. In mountainous terrain, defensive walls such as ''[[letzi]]s'' were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions{{snd}} representing the status and independence of the communities they embraced.

Existing ancient walls are almost always [[masonry]] structures, although brick and timber-built variants are also known. Depending on the [[topography]] of the area surrounding the city or the settlement the wall is intended to protect, elements of the terrain such as rivers or coastlines may be incorporated in order to make the wall more effective.

Walls may only be crossed by entering the appropriate [[city gate]] and are often supplemented with towers. The practice of building these massive walls, though having its origins in prehistory, was refined during the rise of [[city-state]]s, and energetic wall-building continued into the medieval period and beyond in certain parts of Europe.

Simpler defensive walls of earth or stone, thrown up around [[hillfort]]s, [[ringwork]]s, early [[castle]]s and the like, tend to be referred to as [[rampart (fortification)|ramparts]] or banks.