Learn more about Defensive wall
- See also: List of cities with defensive walls
A defensive wall is a fortification used to defend a city 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 value many walls also had important symbolic functions — representing the status and independence of the communities they embraced.
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 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.
Defensive walls are an evolved form of the palisades and other defensive measure employed to protect early settlements. From very early history to modern times, walls have been a near necessity for every city. Exceptions were few — notably, ancient Rome did not have a wall for a long time, choosing to rely on its legions for defense instead.
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, until the Celts were driven away by the immigrating German tribes.
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. The Romans fortified their cities with massive, mortar-bound stone walls. The most famous remainder of this type is the Porta Nigra in Trier, though there also some left in Regensburg and Cologne.
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.
At its simplest, 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 cover the walls.
- 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 European city 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 signalling 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.
In the wake of city growth and the ensuing change of defensive strategy, focussing more on the defense of forts around cities, most city walls were demolished. 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 "gate", "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 modernise 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 preservered 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 primarily serve the purpose of protection of an enclosed settlement. Its primary purpose was to prevent the crossing of the Berlin border between the DDR and the West German exclave of west-Berlin.
Further walls of the 20th century are found in Israel where many exclaves of Jewish settlements are surrounded by fortified walls. 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.
 See also
- List of cities with defensive walls
- Chinese city wall
- City gate
- List of walls
- Stone wall
- Medieval fortification
- Murus Gallicus
- 城壁 (japanese citadel defensive wall)
- Monika Porsche: Stadtmauer und Stadtentstehung — Untersuchungen zur frühen Stadtbefestigung im mittelalterlichen Deutschen Reich. - Hertingen, 2000. ISBN 3-930327-07-4
- Defensive Walls in German Wikipediacs:Hradba