Bastion fort

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A bastion fort or trace italienne (a phrase derived from non-standard French, literally meaning 'Italian outline') is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-fifteenth century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.

Contents

• Origins
• Slopes
• Dead zone
• Enfilade
• Other changes
• Construction
• Effectiveness
• Theories about role in the Military Revolution
• Obsolescence
• See also
• Notes
• References
• External links

The design of the fort is normally a polygon with bastions at the corners of the walls. These outcroppings eliminated protected blind spots, called "dead zones", and allowed fire along the curtain wall from positions protected from direct fire. Many bastion forts also feature cavaliers, which are raised secondary structures based entirely inside the primary structure.

Origins

Their predecessors, medieval fortresses, were usually placed on high hills. From there, arrows were shot at the enemies. The enemies' hope was to either ram the gate or climb over the wall with ladders and overcome the defenders. For the invading force these fortifications proved quite difficult to overcome and, accordingly, fortresses occupied a key position in warfare.

Passive ring-shaped ( Enceinte ) fortifications of the Medieval era proved vulnerable to damage or destruction when attackers directed cannon fire on to perpendicular masonry wall. In addition, attackers that could get close to the wall were able to conduct undermining operations in relative safety, as the defenders could not shoot at them from nearby walls, until the development of machicolation. In contrast, the bastion fortress was a very flat structure composed of many triangular bastions, specifically designed to cover each other, and a ditch. To counteract the cannonballs, defensive walls were made lower and thicker. To counteract the fact that lower walls were easier to climb, the ditch was widened so that attacking infantry were still exposed to fire from a higher elevation, including enfilading fire from the bastions.

The outer side of the ditch was usually provided with a glacis to deflect cannonballs aimed at the lower part of the main wall. Further structures, such as ravelins, tenailles, hornworks or crownworks, and even detached forts could be added to create complex outer works to further protect the main wall from artillery, and sometimes provide additional defensive positions. They were built of many materials, usually earth and brick, as brick does not shatter on impact from a cannonball as stone does. ^[3]

Bastion fortifications were further developed in the late fifteenth and early sixteenth centuries, primarily in response to the French invasion of the Italian peninsula. The French army was equipped with new cannon and bombards that were easily able to destroy traditional fortifications built in the Middle Ages. Star forts were employed by Michelangelo in the defensive earthworks of Florence, and refined in the sixteenth century by Baldassare Peruzzi and Vincenzo Scamozzi. The design spread out of Italy in the 1530s and 1540s.

It was employed heavily throughout Europe for the following three centuries. Italian engineers were heavily in demand throughout Europe to help build the new fortifications. The late-seventeenth-century architects Menno van Coehoorn and especially Vauban, Louis XIV's military engineer, are considered to have taken the form to its logical extreme. "Fortresses... acquired ravelins and redoubts, bonnettes and lunettes, tenailles and tenaillons, counterguards and crownworks and hornworks and curvettes and faussebrayes and scarps and cordons and banquettes and counterscarps..." ^[4]

The star-shaped fortification had a formative influence on the patterning of the Renaissance ideal city: "The Renaissance was hypnotized by one city type which for a century and a half—from Filarete to Scamozzi—was impressed upon all utopian schemes: this is the star-shaped city". ^[5] In the nineteenth century, the development of the explosive shell changed the nature of defensive fortifications. Elvas, in Portugal is considered by some to be the best surviving example of the Dutch school of fortifications.

Other changes

Thus forts evolved complex shapes that allowed defensive batteries of cannon to command interlocking fields of fire. Forward batteries commanded the slopes which defended walls deeper in the complex from direct fire. The defending cannon were not simply intended to deal with attempts to storm the walls, but to actively challenge attacking cannon and deny them approach close enough to the fort to engage in direct fire against the vulnerable walls.

The key to the fort's defence moved to the outer edge of the ditch surrounding the fort, known as the covered way, or covert way. Defenders could move relatively safely in the cover of the ditch and could engage in active countermeasures to keep control of the glacis, the open slope that lay outside the ditch, by creating defensive earthworks to deny the enemy access to the glacis and thus to firing points that could bear directly onto the walls and by digging counter mines to intercept and disrupt attempts to mine the fort walls.

Compared to medieval fortifications, forts became both lower and larger in area, providing defence in depth, with tiers of defences that an attacker needed to overcome in order to bring cannon to bear on the inner layers of defences.

Firing emplacements for defending cannon were heavily defended from bombardment by external fire, but open towards the inside of the fort, not only to diminish their usefulness to the attacker should they be overcome, but also to allow the large volumes of smoke that the defending cannon would generate to dissipate.

Fortifications of this type continued to be effective while the attackers were armed only with cannon, where the majority of the damage inflicted was caused by momentum from the impact of solid shot. Because only low explosives such as black powder were available, explosive shells were largely ineffective against such fortifications. The development of mortars, high explosives, and the consequent large increase in the destructive power of explosive shells and thus plunging fire rendered the intricate geometry of such fortifications irrelevant. Warfare was to become more mobile. It took, however, many years to abandon the old fortress thinking.

Construction

Bastion forts were very expensive. Amsterdam's 22 bastions cost 11 million florins, and Siena in 1544 bankrupted itself to pay for its defences. For this reason, bastion forts were often improvised from earlier defences. Medieval curtain walls were torn down, and a ditch was dug in front of them. The earth used from the excavation was piled behind the walls to create a solid structure. While purpose-built fortifications would often have a brick fascia because of the material's ability to absorb the shock of artillery fire, many improvised defences cut costs by leaving this stage out and instead opting for more earth. Improvisation could also consist of lowering medieval round towers and infilling them with earth to strengthen the structures.

It was also often necessary to widen and deepen the ditch outside the walls to create a more effective barrier to frontal assault and mining. Engineers from the 1520s were also building massive, gently sloping banks of earth called glacis in front of ditches so that the walls were almost totally hidden from horizontal artillery fire. The main benefit of the glaces was to deny enemy artillery the ability to fire point-blank. The lower the angle of elevation, the higher the stopping power.

The first key instance of a trace Italianate was at the Papal port of Civitavecchia, where the original walls were lowered and thickened because the stone tended to shatter under bombardment.

Effectiveness

The first major battle which truly showed the effectiveness of trace Italienne was the defence of Pisa in 1500 against a combined Florentine and French army. With the original medieval fortifications beginning to crumble to French cannon fire, the Pisans constructed an earthen rampart behind the threatened sector. It was discovered that the sloping earthen rampart could be defended against escalade and was also much more resistant to cannon fire than the curtain wall it had replaced.

The second siege was that of Padua in 1509. A monk engineer named Fra Giocondo, trusted with the defence of the Venetian city, cut down the city's medieval wall and surrounded the city with a broad ditch that could be swept by flanking fire from gun ports set low in projections extending into the ditch. Finding that their cannon fire made little impression on these low ramparts, the French and allied besiegers made several bloody and fruitless assaults and then withdrew.

The new type of fortification also played a role in the numerous Mediterranean wars, slowing down the Ottoman expansion. Although Rhodes had been partially upgraded to the new type of fortifications after the 1480 siege, it was still conquered in 1522; nevertheless it was a long and bloody siege, and the besieged had no hope of outside relief because the island was close to the Ottoman power base and far from any allies. On the other hand, the Ottomans failed to take Corfu in 1537 in no small part because of the new fortifications, and several attempts spanning almost two centuries (another major one was in 1716) also failed. ^{[8] [9]}

Two star forts were built by the Order of Saint John on the island of Malta in 1552, Fort Saint Elmo and Fort Saint Michael. Fort Saint Elmo played a critical role in the Ottoman siege of 1565 when it managed to hold out heavy bombardment for over a month. Eventually it fell, but the Ottoman casualties were very high, and it bought time for the relief force which arrived from Sicily to relieve the rest of the besieged island. The star fort therefore played a crucial and decisive role in the siege. ^[10]

After the fall of Venice to Napoleon, Corfu was occupied in 1797 by the French republican armies. The now ancient fortifications were still of some value at this point. A Russian–Ottoman–English alliance led at sea by Admiral Ushakov and with troops sent by Ali Pasha retook Corfu in 1799 after a four-month siege, when the garrison led by general Louis François Jean Chabot, being short of provisions and having lost the key island of Vido at the entrance of the port, surrendered and was allowed passage back to France. ^{[11] [12]}

Theories about role in the Military Revolution

The Military Revolution thesis originally proposed by Michael Roberts in 1955, as he focused on Sweden (1560–1660) searching for major changes in the European way of war caused by the introduction of portable firearms. Roberts linked military technology with larger historical consequences, arguing that innovations in tactics, drill and doctrine by the Dutch and Swedes (1560–1660), which maximized the utility of firearms, led to a need for more trained troops and thus for permanent forces (standing armies).

According to Geoffrey Parker in his article, The Military Revolution 1560–1660: A Myth?, the appearance of the trace Italienne in early modern Europe, and the difficulty of taking such fortifications, is what resulted in a profound change in military strategy, most importantly, Parker argued, an increase in army sizes necessary to attack these forts. "Wars became a series of protracted sieges", Parker suggests, and open-pitch battles became "irrelevant" in regions where the trace Italienne existed. Ultimately, Parker argues, "military geography", in other words, the existence or absence of the trace Italienne in a given area, shaped military strategy in the early modern period. This is a profound alteration of the Military Revolution thesis.

Parker's emphasis on the fortification as the key element has attracted substantial criticism from some academics, such as John A. Lynn and M. S. Kingra, particularly with respect to the claimed causal link between the new fortress design and increases in army sizes during this period. ^[13]

Obsolescence

In the nineteenth century, with the development of more powerful artillery and explosive shells, star forts were replaced by simpler but more robust polygonal forts. In the twentieth century, with the development of tanks and aerial warfare during and after the First World War, fixed fortifications became and have remained less important than in previous centuries.

Star forts reappeared during the early twenty-first-century French intervention in Mali where they were built by the 17th Parachute Engineer Regiment. ^[14]

See also

• Battlement
• Erik Dahlberg
• List of established military terms
• List of bastion forts
• Mathematics and architecture
• Menno van Coehoorn
• Sébastien Le Prestre de Vauban
• Suomenlinna
• Venetian Works of Defence between the 16th and 17th centuries: Stato da Terra – Western Stato da Mar

Notes

Related Research Articles

A siege is a military blockade of a city, or fortress, with the intent of conquering by attrition, or by well-prepared assault. Siege warfare is a form of constant, low-intensity conflict characterized by one party holding a strong, static, defensive position. Consequently, an opportunity for negotiation between combatants is common, as proximity and fluctuating advantage can encourage diplomacy.

A glacis in military engineering is an artificial slope as part of a medieval castle or in early modern fortresses. They may be constructed of earth as a temporary structure or of stone in more permanent structure. More generally, a glacis is any slope, natural or artificial, which fulfils the above requirements. The etymology of this French word suggests a slope made dangerous with ice, hence the relationship with glacier.

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 palisades or earthworks to extensive military fortifications such as curtain walls with towers, bastions and gates for access to the city. 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 letzis were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced.

A fortification is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere.

A bastion or bulwark is a structure projecting outward from the curtain wall of a fortification, most commonly angular in shape and positioned at the corners of the fort. The fully developed bastion consists of two faces and two flanks, with fire from the flanks being able to protect the curtain wall and the adjacent bastions. Compared with the medieval fortified towers they replaced, bastion fortifications offered a greater degree of passive resistance and more scope for ranged defence in the age of gunpowder artillery. As military architecture, the bastion is one element in the style of fortification dominant from the mid 16th to mid 19th centuries.

Fort George is a large 18th-century fortress near Ardersier, to the north-east of Inverness in the Highland council area of Scotland. It was built to control the Scottish Highlands in the aftermath of the Jacobite rising of 1745, replacing a Fort George in Inverness constructed after the 1715 Jacobite rising to control the area. The current fortress has never been attacked and has remained in continuous use as a garrison.

A ravelin is a triangular fortification or detached outwork, located in front of the innerworks of a fortress. Originally called a demi-lune, after the lunette, the ravelin is placed outside a castle and opposite a fortification curtain wall.

A caponier is a type of defensive structure in a fortification. Fire from this point could cover the ditch beyond the curtain wall to deter any attempt to storm the wall. The word originates from the French caponnière, meaning "chicken coop".

The Siege of Rhodes of 1522 was the second and ultimately successful attempt by the Ottoman Empire to expel the Knights of Rhodes from their island stronghold and thereby secure Ottoman control of the Eastern Mediterranean. The first siege in 1480 had been unsuccessful. Despite very strong defenses, the walls were demolished over the course of six months by Turkish artillery and mines.

Sapping is a term used in siege operations to describe the digging of a covered trench to approach a besieged place without danger from the enemy's fire. The purpose of the sap is usually to advance a besieging army's position towards an attacked fortification. It is excavated by specialised military units, whose members are often called sappers.

A curtain wall is a defensive wall between fortified towers or bastions of a castle, fortress, or town.

In military engineering, a ditch is an obstacle designed to slow down or break up an attacking force, while a trench is intended to provide cover to the defenders. In military fortifications the side of a ditch farthest from the enemy and closest to the next line of defence is known as the scarp while the side of a ditch closest to the enemy is known as the counterscarp.

A Carnot wall is a type of loop-holed wall built in the ditch of a fort or redoubt. It takes its name from the French mathematician, politician, and military engineer Lazare Carnot. Such walls were introduced into the design of fortifications from the early nineteenth century. As conceived by Carnot, they formed part of an innovative but controversial system of fortification intended to defend against artillery and infantry attack. Carnot walls were employed, together with other elements of Carnot's system, in continental Europe in the years after the final defeat of Napoleon in 1815, especially by the Prussians, other Germans and Austrians. Their adoption was initially resisted by the French themselves and by the British.

The fortifications of the town of Rhodes are shaped like a defensive crescent around the medieval town and consist mostly of a fortification composed of a huge wall made of an embankment encased in stone, equipped with scarp, bastions, moat, counterscarp and glacis. The portion of fortifications facing the harbour is instead composed of a crenellated wall. On the moles, towers and defensive forts are found.

In fortification architecture, a rampart is a length of embankment or wall forming part of the defensive boundary of a castle, hillfort, settlement or other fortified site. It is usually broad-topped and made of excavated earth and/or masonry.

The fortifications of Mdina are a series of defensive walls which surround Mdina, the former capital city of Malta from antiquity to the medieval period. The city was founded as Maleth by the Phoenicians in around the 8th century BC, and it later became part of the Roman Empire under the name Melite. The ancient city was surrounded by walls, but very few remains of these have survived.

The siege of Ath was a siege of the Nine Years' War. The French stockpiled 266,000 French pounds of gunpowder for the siege and used less than half of it. Consumption of other material amounted to 34,000 pounds of lead, 27,050 cannonballs, 3,400 mortar bombs, 950 grenades and 12,000 sandbags. The financial costs were 89,250 French livres. After the garrison's capitulation, 6,000 peasant workers filled up the trenches. Of the 62 French engineers present, two were killed and seven seriously wounded. This demonstration of French military potency, combined with the successful storming of Barcelona the same year, convinced the Allies to come to terms with France in the treaty of Ryswick, thus ending the war.

Timișoara Fortress is a historical fortress in western Romania around which the town of Timișoara was built.

A palanka, also known as parkan in Southern Hungary and palanga, was a wooden fortification used by the Ottoman Empire extensively in certain regions of Southeast Europe, including Hungary, the Balkans and the Black Sea coast against rival states, especially the Archduchy of Austria and the Kingdom of Hungary. Such wooden forts could be built and expanded quickly, and usually contained a small garrison. These fortifications varied in size and shape but were primarily constructed of palisades. Palankas could be adjacent to a town and later they could be replaced by a more formidable stone fortress as in the case of Uyvar. Palankas could also be built as an extension of the main fortress. Many Ottoman forts were a mixture of palanka type fortifications and stonework. Evliya Çelebi describes the word palanka also as a technique of timber masonry.

References

• af Hällström, Olof (2004) Sveaborg – The island fortress off Helsinki, ISBN   978-952-91-7378-5
• Duffy, C. (1975) Fire & Stone, The Science of Fortress Warfare 1660–1860, ISBN   978-0-7858-2109-0

External links

Wikimedia Commons has media related to Star forts .

• Cataneo, Hieronymus, De arte bellica, sive, De designandis ac construendis arcibus & propugnaculis, necnon & de ijs oppugnandis, expugnandis, ac propugnandis: de itinere exercitus, ac castrametatione: quando expediat manus cum hoste conserere, ac tandem, quid imperatori sit in procinctu cauendum vel eligendum, (1600)
• Bastion fort at World Atlas
• Star castle in Netherlands