A defensive wall is a fortification used to defend a city or settlement from potential aggressors. In 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, Hadrian's Wall, and the metaphorical Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. Beyond their defensive utility many walls also had important symbolic functions — 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 (e.g. 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. In the Middle Ages, the right of a settlement to build a defensive wall was a privilege, and was usually granted by the so-called "right of crenellation" on a medieval fortification. The practice of building these massive walls, though having its origins in prehistory, was refined during the rise of city-states, and energetic wall-building continued into the medieval period and beyond in certain parts of Europe.

History

From very early history to modern times, walls have been a near necessity for every city.Uruk in ancient Sumer (Mesopotamia) is one of the world's oldest known walled cities. Before that, the city (or rather proto-city) of Jericho in what is now the West Bank had a wall surrounding it as early as the 8th millennium BC.

The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.

Some settlements in the Indus Valley Civilization were also fortified. By about 3500 B.C., hundreds of small farming villages dotted the Indus floodplain. Many of these settlements had fortifications and planned streets. The stone and mud brick houses of Kot Diji were clustered behind massive stone flood dykes and defensive walls, for neighboring communities quarreled constantly about the control of prime agricultural land. Mundigak (c. 2500 B.C.) in present day south-east Afghanistan has defensive walls and square bastions of sun dried bricks.

Babylon was one of the most famous cities of the ancient world, especially as a result of the building program of Nebuchadnezzar, who expanded the walls and built the Ishtar Gate.

Exceptions were few — notably, ancient Sparta and ancient Rome did not have walls for a long time, choosing to rely on their militaries for defense instead. Initially, these fortifications were simple constructions of wood and earth, which were later replaced by mixed constructions of stones piled on top of each other without mortar.

In Central Europe, the Celts built large fortified settlements known as oppida, whose walls seem partially influenced by those built in the Mediterranean.The fortifications were continuously expanded and improved.

In ancient Greece, large stone walls had been built in Mycenaean Greece, such as the ancient site of Mycenae (famous for the huge stone blocks of its 'cyclopean' walls). In classical era Greece, the city of Athens built a long set of parallel stone walls called the Long Walls that reached their guarded seaport at Piraeus.

Large tempered earth (ie. rammed earth) walls were built in ancient China since the Shang Dynasty (c. 1600-1050 BC), as the capital at ancient Ao had enormous walls built in this fashion (see siege for more info). Although stone walls were built in China during the Warring States (481-221 BC), mass conversion to stone architecture did not begin in earnest until the Tang Dynasty (618-907 AD). In terms of China's longest and most impressive fortification, the Great Wall had been built since the Qin Dynasty (221-207 BC), although its present form was mostly an engineering feat and remodeling of the Ming Dynasty (1368-1644 AD) during the 15th and 16th centuries. The large walls of Pingyao serve as one example. Likewise, the famous walls of the Forbidden City in Beijing were established in the early 15th century by the Yongle Emperor.

The Romans fortified their cities with massive, mortar-bound stone walls.The most famous of these are the largely extant Aurelian Walls of Rome and the Theodosian Walls of Constantinople, together with partial remains elsewhere. These are mostly city gates, like the Porta Nigra in Trier or Newport Arch in Lincoln.

Apart from these, the early Middle Ages also saw the creation of some towns built around castles. These cities were only rarely protected by simple stone walls and more usually by a combination of both walls and ditches.From the 12th century AD hundreds of settlements of all sizes were founded all across Europe, who very often obtained the right of fortification soon afterwards.

The founding of urban centers was an important means of territorial expansion and many cities, especially in eastern Europe, were founded precisely for this purpose during the period of Eastern Colonisation. These cities are easy to recognise due to their regular layout and large market spaces. The fortifications of these settlements were continuously improved to reflect the current level of military development.

During the Renaissance era, the Venetians raised great walls around cities threatened by the Ottoman empire. The finest examples are, among others, in Nicosia (Cyprus) and Chania (Crete), which still stand to this day.

Composition

At its most simple, a defensive wall consists of a wall enclosure and its gates. For the most part, the top of the walls were accessible, with the outside of the walls having tall parapets with embrasures or merlons. North of the Alps, this passageway at the top of the walls occasionally had a roof.

In addition to this, many different enhancements were made over the course of the centuries:

• City ditch: a ditch dug in front of the walls, occasionally filled with water.
• Gate tower: a tower built next to, or on top of the city gates to better defend the city gates.
• Wall tower: a tower built on top of a segment of the wall, which usually extended outwards slightly, so as to be able to observe the exterior of the walls on either side. In addition to arrow slits, ballistae, catapults and cannons could be mounted on top for extra defence.
• Pre-wall: wall built outside the wall proper, usually of lesser height — the space in between was usually further subdivided by additional walls.
• Additional obstacles in front of the walls.

The defensive towers of west and south European fortifications in the Middle Ages were often very regularly and uniformly constructed (cf. Ávila, Provins), whereas Central Europeancity walls tend to show a variety of different styles.In these cases, the gate and wall towers often reach up to considerable heights, and gates equipped with two towers on either side are much rarer.Apart from the purely military, defensive purpose, towers also played an important representative and artistic role in the conception of a fortified complex. In many senses, the architecture of the city thus competed with that of the castle of the noblemen and city walls were often a manifestation of the pride of a particular city.

Urban areas outside the city walls, so-called Vorstädte, were often enclosed by their own set of walls and integrated into the defense of the city. These areas were often inhabited by the poorer population and held the "noxious trades". In many cities, a new wall was built once the city had grown outside of the old wall. This can often still be seen in the layout of the city, for example in Nördlingen, and sometimes even a few of the old gate towers are preserved, such as the white tower in Nürnberg.Additional constructions prevented the circumvention of the city, through which many important trade routes passed, thus ensuring that tolls were paid when the caravans passed through the city gates, and that the local market was visited by the trade caravans.Furthermore, additional signaling and observation towers were frequently built outside the city, and were sometimes fortified in a castle-like fashion. The border of the area of influence of the city was often partially or fully defended by elaborate ditches, walls and/or hedges.The crossing points were usually guarded by gates or gate houses.These defenses were regularly checked by riders, who often also served as the gate keepers. Long stretches of these defenses can still be seen to this day, and even some gates are still intact.To further protect their territory, rich cities also established castles in their area of influence.A famous example of this practice is the Romanian "Dracula Castle" at Bran/Törzburg, which was intended to protect Kronstadt (today's Braşov).

The city walls were often connected to the fortifications of hill castles via additional walls .Thus the defenses were made up of city and castle fortifications taken together. Several examples of this are preserved, for example in Germany Hirschhorn on the Neckar, Königsberg and Pappenheim, Franken, Burghausen in Oberbayern and many more.A few castles were more directly incorporated into the defensive strategy of the city (e.g. Nürnberg, Zons, Carcassonne), or the cities were directly outside the castle as a sort of "pre-castle" (Coucy-le-Chateau, Conwy and others). Larger cities often had multiple stewards — for example Augsburg was divided into a Reichstadt and a bishopal (clerical) city. These different parts were often separated by their own fortifications.

With the development of firearms came the necessity to expand the existing installation, which occurred in multiples stages. Firstly, additional, half-circular towers were added in the interstices between the walls and pre-walls (s.a.) in which a handful of cannons could be placed. Soon after, reinforcing structures — or "bastions" — were added in strategically relevant positions, e.g. at the gates or corners. A well-preserved example of this is the Spitalbastei in Rothenburg. However, at this stage the cities were still only protected by relatively thin walls which could offer little resistance to the cannons of the time. Therefore new, star forts with numerous cannons and thick earth walls reinforced by stone were built. These could resist cannon fire for prolonged periods of time. However, these massive fortifications severely limited the growth of the cities, as it was much more difficult to move them as compared to the simple walls previously employed — to make matters worse, it was forbidden to build "outside the city gates" for strategic reasons and the cities became more and more densely populated as a result.

Decline

In the wake of city growth and the ensuing change of defensive strategy, focusing more on the defense of forts around cities, most city walls were demolished. Also, the invention of gunpowder rendered walls less effective, as siege cannons could then be used to blast through walls, allowing armies to simply walk through. Nowadays, the presence of former city fortifications can often only be deduced from the presence of ditches or parks.

Furthermore, some street names hint at the presence of fortifications in times past, for example when words such as "wall" or "glacis" occur.

In the 19th century, less emphasis was placed on preserving the fortifications for the sake of their architectural or historical value — on the one hand, complete fortifications were restored (Carcassonne), on the other hand many structures were demolished in an effort to modernize the cities. A notable exception in this is the "monument preservation" law by the Bavarian King Ludwig I of Bavaria, which led to the nearly complete preservation of many impressive monuments such as the Rothenburg ob der Tauber, Nördlingen and Dinkelsbühl.The countless small fortified towns in the Franken region were also preserved as a consequence of this edict.

Modern era

Walls and fortified wall structures were built in the modern era, too. They did not, however have the original purpose of being a structure able to resist a prolonged siege or bombardment.

Berlin's city wall from the 1730s to the 1860s was partially made of wood. Its primary purpose was to enable the city to impose tolls on goods and, secondarily, also served to prevent the desertion of soldiers from the garrison in Berlin.

The Berlin wall was a different form of wall, in that it did not exclusively serve the purpose of protection of an enclosed settlement. One of its purposes was to prevent the crossing of the Berlin border between the GDR and the West German exclave of west-Berlin.

Defensive walls have been built in Korea along the De-militarised Zone.

Further walls of the 20th century are found in Israel where many exclaves of Jewish settlements are surrounded by fortified walls, as are many parts of Belfast, Northern Ireland by the Belfast Peace Lines.

Additionally, in some countries, different embassies may be grouped together in a single "embassy district," enclosed by a fortified complex with walls and towers — this usually occurs in regions where the embassies run a high risk of being target of attacks.

Most of these "modern" city walls are made of steel and concrete. Vertical concrete plates are put together so as to allow the least space in between them, and are rooted firmly in the ground.The top of the wall is often protruding and beset with barbed wire in order to make climbing them more difficult. These walls are usually built in straight lines and covered by watchtowers at the corners. Double walls, i.e. two walls with an interstitial "zone of fire" (cf. the Berlin wall) are rare.

The only extant city walls in North America are the historic ones in Old Quebec City, Canada.

See also

• List of cities with defensive walls
• Chinese city wall
• Citadel
• City gate
• Fortification
• List of walls
• Wall
• Stone wall
• Medieval fortification
• Siege
• Murus Gallicus
• Mural crown

Notes

References

• Monika Porsche: Stadtmauer und Stadtentstehung — Untersuchungen zur frühen Stadtbefestigung im mittelalterlichen Deutschen Reich. - Hertingen, 2000. ISBN 3-930327-07-4
• Defensive Walls in German Wikipedia