Fortifications are
military constructions and
buildings designed for
defense in
warfare and
military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the
Latin fortis ("strong") and
facere ("to make").
Nomenclature
Many military installations are known as
forts, although they are not always fortified. Larger forts may class as
fortresses, smaller ones formerly often bore the name of
fortalices. The word fortification can also refer to the practice of improving an area's defense with defensive works.
City walls are fortifications but not necessarily called fortresses.
The art of setting out a military camp or constructing a fortification traditionally classifies as
castramentation, since the time of the
Roman legions. The
art/
science of laying
siege to a fortification and of destroying it has the popular name of
siegecraft or 'siege warfare' and the formal name of
poliorcetics. In some texts this latter term also applies to the art of building a fortification.
Fortification is usually divided into two branches, namely
permanent fortification and
field fortification. Permanent fortifications are erected at leisure, with all the resources that a state can supply of constructive and
mechanical skill, and are built of enduring materials. Field fortifications are extemporized by troops in the field, perhaps assisted by such local labor and tools as may be procurable and with materials that do not require much preparation, such as
earth, brushwood and light
timber, or sandbags (see
sangar).
There is also an intermediate branch known as
semipermanent fortification. This is employed when in the course of a campaign it becomes desirable to protect some locality with the best imitation of permanent defences that can be made in a short time, ample resources and skilled civilian labor being available.
Castles are fortifications which are regarded as being distinct from the generic fort or fortress in that it describes a residence of a monarch or noble and commands a specific defensive territory.
History
Ancient
Artists impression of the battlements at
Buhen fortress in Egypt about 1800BC
From very early history to modern times,
walls have been a necessity for many cities.
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 Ancient Egyptians also built fortresses on the frontiers of the Nile Valley to protect against invaders from its neighboring territories. Many of the fortifications of the ancient world were built with mud brick, leaving many no more than mounds of dirt for today's archaeologists.
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.
The Aurelian Walls
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). 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.
Hadrian's Wall was built by the
Roman Empire across the width of what is now
northern England following a visit by
Roman Emperor Hadrian (AD 76–138) in AD 122.
Medieval
Roman forts and
hill forts were the main antecedents of
castles in
Europe, which emerged in the 9th century in the
Carolingian Empire.
The
Early Middle Ages 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, which 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), and they still stand, to this day.
Early Modern
Medieval-style fortifications were largely made obsolete by the arrival of
cannons on the 14th century battlefield. Fortifications in the age of
blackpowder evolved into much lower structures with greater use of
ditches and earth ramparts that would absorb and disperse the energy of cannon fire. Walls exposed to direct cannon fire were very vulnerable, so were sunk into ditches fronted by earth slopes.
This placed a heavy emphasis on the geometry of the fortification to allow defensive cannonry interlocking fields of fire to cover all approaches to the lower and thus more vulnerable walls. Fortifications also extended in depth, with protected batteries for defensive cannonry, to allow them to engage attacking cannon to keep them at a distance and prevent them bearing directly on the vulnerable walls.
The result was
star shaped fortifications with tier upon tier of hornworks and
bastions, of which
Bourtange illustrated to the right is an excellent example. There are also extensive fortifications from this era in the
Nordic states and in
Britain, the fortifications of
Berwick-upon-Tweed and the harbour archipelago of
Suomenlinna at Helsinki being fine examples.
19th Century
The arrival of
explosive shells in the nineteenth century led to yet another stage in the evolution of fortification. Star forts of the cannon era did not fare well against the effects of high explosive and the intricate arrangements of bastions, flanking batteries and the carefully constructed lines of fire for the defending cannon could be rapidly disrupted by explosive shells.
Worse, the large open ditches surrounding forts of this type were an integral part of the defensive scheme, as was the covered way at the edge of the counter scarp. The ditch was extremely vulnerable to bombardment with explosive shells.
In response, military engineers evolved the
polygonal style of fortification. The ditch became deep and vertically sided, cut directly into the native rock or soil, laid out as a series of straight lines creating the central fortified area that gives this style of fortification its name.
Wide enough to be an impassable barrier for attacking troops, but narrow enough to be a difficult target for enemy shellfire, the ditch was swept by fire from defensive blockhouses set in the ditch as well as firing positions cut into the outer face of the ditch itself.
The profile of the fort became very low indeed, surrounded outside the ditch by a gently sloping open area so as to eliminate possible cover for enemy forces, while the fort itself provided a minimal target for enemy fire. The entrypoint became a sunken gatehouse in the inner face of the ditch, reached by a curving ramp that gave access to the gate via a rolling bridge that could be withdrawn into the gatehouse.
thumb|left|Inside an underground tunnel network within the Middle Head Fortifications in Sydney
Much of the fort moved underground, with deep passages and
tunnels to connect the
blockhouses and firing points in the ditch to the fort proper, with
magazines and machine rooms deep under the surface.
The guns however, were often mounted in open emplacements and protected only by a
parapet - both in order to keep a lower profile and also because experience with guns in closed
casemates had seen them put out of action by rubble as their own casemates were collapsed around them.
20th Century
Steel-and-
concrete fortifications were common during the 19th and early 20th centuries, however the advances in modern warfare since
World War I have made large-scale fortifications obsolete in most situations. Only underground
bunkers are still able to provide some protection in modern wars. Many historical fortifications were demolished during the modern age, but a considerable number survive as popular tourist destinations and prominent local
landmarks today.
The downfall of permanent fortifications had two causes:
- The ever escalating power of artillery and air power meant that almost any target that could be located could be destroyed, if sufficient force was massed against it. As such, the more resources a defender devoted to reinforcing a fortification, the more combat power that fortification justified being devoted to destroying it, if the fortification's destruction was demanded by an attacker's strategy.
- The second weakness of permanent fortification was its very permanency. Because of this it was often easier to go around a fortification, and with the rise of mobile warfare in the beginning of World War II this became a viable offensive choice. When a defensive line was too extensive to be entirely bypassed, massive offensive might could be massed against one part of the line allowing a breakthrough, after which the rest of the line could be bypassed. Such was the fate of the many defensive lines built before and during World War II, such as the Maginot Line, the Siegfried Line, the Stalin Line and the Atlantic Wall. (In the case of the Atlantic Wall, the purpose of the fortification was to delay an invasion to allow reinforcement.)
Instead field fortification rose to dominate defensive action. Unlike the
trench warfare which dominated
World War I these defenses were more temporary in nature. This was an advantage because since it was less extensive it formed a less obvious target for enemy force to be directed against.
If sufficient power was massed against one point to penetrate it, the forces based there could be withdrawn and the line could be re-established relatively quickly. Instead of a supposedly impenetrable defensive line, such fortifications emphasized
defense in depth, so that as defenders were forced to pull back or were over-run, the lines of defenders behind them could take over the defense.
Because the mobile offensives practiced by both sides usually focused on avoiding the strongest points of a defensive line, these defenses were usually relatively thin and spread along the length of a line. The defense was usually not equally strong throughout however.
The strength of the defensive line in an area varied according to how rapidly an attacking force could progress in the terrain that was being defended - both the terrain the defensive line was built on and the ground behind it that an attacker might hope to break out into. This was both for reasons of the strategic value of the ground, and its defensive value.
This was possible because while offensive tactics were focused on mobility, so were defensive tactics. The dug in defenses consisted primarily of infantry and antitank guns. Defending tanks and tank destroyers would be concentrated in mobile "fire brigades" behind the defensive line. If a major offensive was launched against a point in the line, mobile reinforcements would be sent to reinforce that part of the line that was in danger of failing.
Thus the defensive line could be relatively thin because the bulk of the fighting power of the defenders was not concentrated in the line itself but rather in the mobile reserves. A notable exception to this rule was seen in the defensive lines at the
Battle of Kursk during
World War II, where
German forces deliberately attacked into the strongest part of the
Soviet defenses seeking to crush them utterly.
The terrain that was being defended was of primary importance because open terrain that tanks could move over quickly made possible rapid advances into the defenders' rear areas that were very dangerous to the defenders. Thus such terrain had to be defended at all cost.
In addition, since in theory the defensive line only had to hold out long enough for mobile reserves to reinforce it, terrain that did not permit rapid advance could be held more weakly because the enemy's advance into it would be slower, giving the defenders more time to reinforce that point in the line. For example the
battle of the Hurtgen Forest in
Germany during the closing stages of
World War II is an excellent example of how impassable terrain could be used to the defenders' advantage.
Forts
Forts in modern usage often refer to space set aside by governments for a permanent military facility; these often do not have any actual fortifications, and can have specializations (military barracks, administration, medical facilities, or intelligence). In the
United States usage, forts specifically refer to
Army fortifications;
Marine Corps fortifications are referred to as
camps.
However there are some modern fortifications that are referred to as forts. These are typically small semi permanent fortifications. In urban combat they are built by upgrading existing structures such as houses or public buildings. In field warfare they are often log, sandbag or gabion type construction.
Such forts are typically only used in low level conflict, e.g., counterinsurgency conflicts or very low level conventional conflicts, e.g., the
Indonesia–Malaysia confrontation saw the use of log forts for use by forward platoons and companies. The reason for this is that static above ground forts can not survive modern direct or indirect fire weapons larger than mortars, RPGs and small arms.
American West
Forts in the
American Old West during the
Indian Wars were lightly fortified enclosures with log or
adobe walls. They were sometimes only fortified
trading posts or a combination of a trading post and an Army post. Famous forts included
Fort Laramie and
Fort Bridger on the
Overland Trail and
Bent's Fort on the Arkansas River.
See also
The Kumbhalgarh Fort in Rajasthan, India is one of the longest forts in Asia. The Fort was built by Rana Kumbha in the 15th century and more than 350 Hindu and Jain temples are located within it. For more than 3 centuries, the Fort remained impregnable until it was taken by the combined forces of Akbar, Malwa and the Gujarat Sultanate. 
Rödberget fort, a part of the modern
Boden Fortress in
Sweden, seen from the north. The
moat and the armored
turrets are clearly visible, as well as the magnificent view one has from the fort.
Petrovaradin fortress "Gibraltar on the Danube" - Austrian fortress from XVIII century and one of the best preserved fortifications in Serbia. 
View of Alamghiri Gate of Lahore Fort.
- Grad, a Slavic wooden fortified settlement
- Pā a 19th-century Māori fortification
Historical FortressesFortification and siege warfareFamous experts
