A fortification is a military construction or building designed for the defense of territories in , and is also used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere ("to make").
From very early history to modern times, have often been necessary for cities to survive in an ever-changing world of invasion and conquest. Some settlements in the Indus Valley Civilization were the first small cities to be fortified. 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). A Greek phrourion was a fortified collection of buildings used as a military garrison, and is the equivalent of the ancient Roman castellum or English language fortress. These constructions mainly served the purpose of a watch tower, to guard certain roads, passes, and borders. Though smaller than a real fortress, they acted as a border guard rather than a real strongpoint to watch and maintain the border.
The art of setting out a military camp or constructing a fortification traditionally has been called "castrametation" since the time of the . Fortification is usually divided into two branches: permanent fortification and field fortification. There is also an intermediate branch known as semi-permanent fortification. are fortifications which are regarded as being distinct from the generic fort or fortress in that they are a residence of a monarch or Nobility and command a specific defensive territory.
Medieval-style fortifications were largely made obsolete by the arrival of in the 14th century. Fortifications in the age of black powder 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 the walls were sunk into ditches fronted by earth slopes to improve protection.
The arrival of in the 19th century led to yet another stage in the evolution of fortification. 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. Steel-and-concrete fortifications were common during the 19th and early 20th centuries. The advances in modern warfare since World War I have made large-scale fortifications obsolete in most situations.
The art of setting out a military camp or constructing a fortification traditionally has been called since the time of the . The art/science of laying siege to a fortification and of destroying it is commonly called siegecraft or siege warfare and is formally known as poliorcetics. In some texts this latter term also applies to the art of building a fortification.
Fortification is usually divided into two branches: 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—for example breastworks—and often known as fieldworks or earthworks, are extemporized by troops in the field, perhaps assisted by such local labour and tools as may be procurable and with materials that do not require much preparation, such as soil, brushwood and light timber, or sandbags (see sangar). An example of field fortification was the construction of Fort Necessity by George Washington in 1754.
There is also an intermediate branch known as semi-permanent 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 labour being available. An example of this is the construction of Roman forts and in other Roman territories where camps were set up with the intention of staying for some time, but not permanently.
are fortifications which are regarded as being distinct from the generic fort or fortress in that it describes a residence of a monarch or Nobility and commands a specific defensive territory. An example of this is the massive medieval castle of Carcassonne.
A massive prehistoric stone wall surrounded the ancient temple of Ness of Brodgar 3200 BC in Scotland. Named the "Great Wall of Brodgar" it was four metres thick and four metres tall. The wall had some symbolic or ritualistic function. The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.Banister Fletcher's A History of Architecture By Banister Fletcher, Sir, Dan Cruickshank, Dan Cruickhank, Sir Banister Fletcher. 1996 Architectural Press. Architecture. 1696 pages. . p. 20
In Central Europe, the Celts built large fortified settlements known as oppidum, whose walls seem partially influenced by those built in the Mediterranean. The fortifications were continuously being expanded and improved. Around 600 BC, in Heuneburg, Germany, forts were constructed with a limestone foundation supported by a mudbrick wall approximately 4 metres tall, probably topped by a roofed walkway, thus reaching a total height of 6 metres. The wall was clad with lime plaster, regularly renewed. Towers protruded outwards from it. The Oppidum of Manching (German: Oppidum von Manching) was a large Celtic proto-urban or city-like settlement at modern-day Manching (near Ingolstadt), Bavaria (Germany). The settlement was founded in the 3rd century BC and existed until c. 50–30 BC. It reached its largest extent during the late La Tène period (late 2nd century BC), when it had a size of 380 hectares. At that time, 5,000 to 10,000 people lived within its 7.2 km long walls. The oppidum of Bibracte is another example of a Gaulish fortified settlement.
The ancient Rome 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.
In addition to the Great Wall, a number of Chinese cities also employed the use of to defend their cities. Notable Chinese city walls include the city walls of Hangzhou, Nanjing, the Old City of Shanghai, Suzhou, Xi'an and the walled villages of Hong Kong. The famous walls of the Forbidden City in Beijing were established in the early 15th century by the Yongle Emperor. The Forbidden City made up the inner portion of the Beijing city fortifications.
Partial listing of Spanish forts:
The Igorot people built forts made of stone walls that averaged several meters in width and about two to three times the width in height around 2000 BC. Ancient and Pre-Spanish Era of the Philippines . Accessed September 04, 2008.
The Muslim Filipinos of the south built strong fortresses called kota or moong to protect their communities. Usually, many of the occupants of these kotas are entire families rather than just warriors. Lords often had their own kotas to assert their right to rule, it served not only as a military installation but as a palace for the local Lord. It is said that at the height of the Maguindanao Sultanate's power, they blanketed the areas around Western Mindanao with Kotas and other fortifications to block the Spanish advance into the region. These kotas were usually made of stone and bamboo or other light materials and surrounded by trench networks. As a result, some of these kotas were burned easily of destroyed. With further Spanish campaigns in the region, the Sultanate was subdued and majority of Kotas dismantled or destroyed. Kotas were not only used by the Muslims as defense against Spaniards and other foreigners, renegades and rebels also built fortifications in defiance of other chiefs in the area. During the American occupation, rebels built strongholds and the Datus, Rajahs or Sultans often built and reinforced their kotas in a desperate bid to maintain rule over their subjects and their land. Many of these forts were also destroyed by American expeditions, as a result, very very few kotas still stand to this day.
During the Siege of Ta'if in January 630, Note: Shawwal 8AH is January 630AD Muhammad ordered his followers to attack enemies who fled from the Battle of Hunayn and sought refuge in the fortress of Taif.William Muir, The life of Mahomet and history of Islam to the era of the Hegira, Volume 4, p. 142.
A military tactic of the Ashanti Empire was to create powerful log at key points. This was employed in later wars against the British Empire to block British advances. Some of these fortifications were over a hundred yard long, with heavy parallel tree trunks. They were impervious to destruction by artillery fire. Behind these stockades numerous Ashanti soldiers were mobilized to check enemy movement. While formidable in construction, many of these strongpoints failed because Ashanti guns, gunpowder and bullets were poor, and provided little sustained killing power in defense. Time and time again British troops overcame or bypassed the stockades by mounting old-fashioned bayonet charges, after laying down some covering fire.The Ashanti campaign of 1900, (1908) By Sir Cecil Hamilton Armitage, Arthur Forbes Montanaro, (1901) Sands and Co. pgs 130–131
Defensive works were of importance in the tropical African Kingdoms. In the Kingdom of Kongo field fortifications were characterized by trenches and low earthen embankments. Such strongpoints ironically, sometimes held up much better against European cannon than taller, more imposing structures.Thornton, pp. 22–39
The founding of urban centres was an important means of territorial expansion and many cities, especially in eastern Europe, were founded precisely for this purpose during the period of Ostsiedlung. 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 Venetian Republic raised great walls around cities, and the finest examples, among others, are in Nicosia (Cyprus), Rocca di Manerba del Garda (Lombardy) and Palmanova (Italy), or Dubrovnik (Croatia), which proved to be futile against attacks but still stand to this day. Unlike Venetians the Ottomans used to built smaller fortifications but in greater numbers, and only rarely fortified entire settlements such as Počitelj, Vratnik and Jajce in Ottoman Bosnia.
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. The evolution of this new style of fortification can be seen in transitional forts such as SarzanelloHarris, J., "Sarzana and Sarzanello – Transitional Design and Renaissance Designers" , Fort (Fortress Study Group), No. 37, 2009, pp. 50–78 in North West Italy which was built between 1492 and 1502. Sarzanello consists of both crenellated walls with towers typical of the medieval period but also has a ravelin like angular gun platform screening one of the curtain walls which is protected from flanking fire from the towers of the main part of the fort. Another example are the fortifications of Rhodes which were frozen at 1522 so that Rhodes is the only European walled town that still shows the transition between the classical medieval fortification and the modern ones.
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 fort with tier upon tier of hornworks and , of which Fort Bourtange is an excellent example. There are also extensive fortifications from this era in the Northern Europe states and in Great Britain, the fortifications of Berwick-upon-Tweed and the harbour archipelago of Suomenlinna at Helsinki being fine examples.
In response, military engineers evolved the Polygonal fort 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 covered by caponiers 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. Much of the fort moved underground. Deep passages and now connected the 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 had seen them put out of action by rubble as their own casemates were collapsed around them.
Gone were citadels surrounding towns: forts were to be moved to the outside of the cities some 12 km to keep the enemy at a distance so their artillery could not bombard the city center. From now on a ring of forts were to be built at a spacing that would allow them to effectively cover the intervals between them.
The new forts abandoned the principle of the bastion, which had also been made obsolete by advances in arms. The outline was a much simplified polygon, surrounded by a ditch. These forts, built in masonry and shaped stone, were designed to shelter their garrison against bombardment. One organizing feature of the new system involved the construction of two defensive curtains: an outer line of forts, backed by an inner ring or line at critical points of terrain or junctions (see, for example, Séré de Rivières system in France).
Traditional fortification however continued to be applied by European armies engaged in warfare in colonies established in Africa against lightly armed attackers from amongst the indigenous population. A relatively small number of defenders in a fort impervious to primitive weaponry could hold out against high odds, the only constraint being the supply of ammunition.
The downfall of permanent fortifications had two causes:
If sufficient power were 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 defence in depth, so that as defenders were forced to pull back or were overrun, the lines of defenders behind them could take over the defence.
Because the mobile offensives practised by both sides usually focused on avoiding the strongest points of a defensive line, these defences were usually relatively thin and spread along the length of a line. The defence 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 defences consisted primarily of infantry and antitank guns. Defending tanks and tank destroyers would be concentrated in mobile 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 Germany forces deliberately attacked into the strongest part of the Soviet Union defences 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 difficult terrain could be used to the defenders' advantage. After World War II, capable of reaching much of the way around the world were developed, and so speed became an essential characteristic of the strongest militaries and defenses. were developed, so missiles could be fired from the middle of a country and hit cities and targets in another country, and airplanes (and air carriers) became major defenses and offensive weapons (leading to an expansion of the use of airports and airstrips as fortifications). Mobile defenses could be had underwater, too, in the form of nuclear submarines capable of firing missiles. Some bunkers in the mid to late 20th century came to be buried deep inside mountains and prominent rocks, such as Gibraltar and the Cheyenne Mountain Complex. On the ground itself, have been used as hidden defences in modern warfare, often remaining long after the wars that produced them have ended.
Demilitarized zones along borders are arguably another type of fortification, although a passive kind, providing a buffer between potentially hostile militaries.
Munition storage follows safety rules which use fortifications (bunkers and bunds) to provide protection against accident and chain reactions (sympathetic detonations). Weapons for rearming aircraft can be stored in small fortified expense stores closer to the aircraft. At Bien Hoa South Vietnam on the morning of 16 May 1965, as aircraft were being re-fuelled and armed, a chain reaction explosion destroyed 13 aircraft, killed 34 personnel, and injured over 100; this, along with damage and losses of aircraft to enemy attack (by both infiltration and stand off attacks), led to the construction of revetments and shelters to protect aircraft throughout South Vietnam.
Aircrew and ground personnel will need protection during enemy attacks and fortifications range from culvert section "duck and cover" shelters to permanent air-raid shelters. Soft locations with high personnel densities such as accommodation and messing facilities can have limited protection by placing prefabricated concrete walls or barriers around them, examples of barriers are Jersey Barriers, T Barriers or Splinter Protection Units (SPUs). Older fortification may prove useful such as the old 'Yugo' pyramid shelters built in the 1980s which were used by US personnel on 8 Jan 2020 when Iran fired 11 ballistic missiles at Ayn al-Asad Airbase in Iraq.
Fuel is volatile and has to comply with rules for storage which provide protection against accident. Fuel in underground bulk fuel installations is well protected though valves and controls are vulnerable to enemy action. Above ground tanks can be susceptible to attack.
Ground support equipment will need to be protected by fortifications to be usable after an enemy attack.
Permanent (concrete) guard fortifications are safer, stronger, last longer and are more cost effective than sandbag fortifications. Prefabricated positions can be made from concrete culvert sections. The British Yarnold Bunker is made from sections of a concrete pipe.
Guard Towers provide increased field of view but a lower level of protection.
Dispersal and camouflage of assets can supplement fortifications against some forms of airfield attack.
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, such as counterinsurgency conflicts or very low level conventional conflicts, such as the Indonesia–Malaysia confrontation, which saw the use of log forts for use by forward 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.
Types of forts and fortification
Fortification and siege warfare