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. The fully developed bastion consists of two faces and two flanks with fire from the flanks being able to protect the curtain wall and also the adjacent bastions.It is one element in the style of fortification dominant from the mid 16th to mid 19th centuries. Bastion fortifications offered a greater degree of passive resistance and more scope for ranged defense in the age of gunpowder artillery compared with the medieval fortifications they replaced.
By the middle of the 15th century, artillery pieces had become powerful enough to make the traditional medieval round tower and curtain wall obsolete. This was exemplified by the campaigns of Charles VII of France who reduced the towns and castles held by the English during the latter stages of the Hundred Years War, and by the fall of Constantinople in 1453 to the large cannon of the Turkish army.
During the Eighty Years War (1568–1648) Dutch military engineers developed the concepts further by lengthening the faces and shortening the curtain walls of the bastions. The resulting construction was called a bolwerk. To augment this change they placed v-shaped outworks known as ravelins in front of the bastions and curtain walls to protect them from direct artillery fire.
These ideas were further developed and incorporated into the trace italienne forts by Sébastien Le Prestre de Vauban,that remained in use during the Napoleonic Wars.
Bastions differ from medieval towers in a number of respects. Bastions are lower than towers and are normally of similar height to the adjacent curtain wall. The height of towers, although making them difficult to scale, also made them easy for artillery to destroy. A bastion would normally have a ditch in front, the opposite side of which would be built up above the natural level then slope away gradually. This glacis shielded most of the bastion from the attacker's cannon while the distance from the base of the ditch to the top of the bastion meant it was still difficult to scale.
In contrast to typical late medieval towers, bastions (apart from early examples) were flat sided rather than curved. This eliminated dead ground making it possible for the defenders to fire upon any point directly in front of the bastion.
Bastions also cover a larger area than most towers. This allows more cannons to be mounted and provided enough space for the crews to operate them.
Surviving examples of bastions are usually faced with masonry. Unlike the wall of a tower this was just a retaining wall; cannonballs were expected to pass through this and be absorbed by a greater thickness of hard-packed earth or rubble behind. The top of the bastion was exposed to enemy fire, and normally would not be faced with masonry as cannonballs hitting the surface would scatter lethal stone shards among the defenders.
If a bastion was successfully stormed, it could provide the attackers with a stronghold from which to launch further attacks. Some bastion designs attempted to minimise this problem.This could be achieved by the use of retrenchments in which a trench was dug across the rear (gorge) of the bastion, isolating it from the main rampart.
Various kinds of bastions have been used throughout history.
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.
A caponier is a type of defensive structure in a fortification. The word originates from the French caponnière, meaning "chicken coop".
Fort Ricasoli is a bastioned fort in Kalkara, Malta, which was built by the Order of Saint John between 1670 and 1698. The fort occupies a promontory known as Gallows' Point and the north shore of Rinella Bay, commanding the entrance to the Grand Harbour along with Fort Saint Elmo. It is the largest fort in Malta, and it has been on the tentative list of UNESCO World Heritage Sites since 1998, as part of the Knights' Fortifications around the Harbours of Malta.
A bastion fort or trace italienne, 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-15th century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.
Neuf-Brisach is a fortified town and commune of the department of Haut-Rhin in the French region of Alsace. The fortified town was intended to guard the border between France and the Holy Roman Empire and, subsequently, the German states. It was built after the Treaty of Ryswick in 1697 that resulted in France losing the town of Breisach, on the opposite bank of the Rhine. The town's name means New Breisach.
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.
The Cottonera Lines, also known as the Valperga Lines, are a line of fortifications in Cospicua and Birgu, Malta. They were built in the 17th and 18th centuries to form the outer defences of the Three Cities of Birgu, Senglea and Cospicua. They surrounded an earlier line of fortifications, known as the Santa Margherita Lines.
The Floriana Lines are a line of fortifications in Floriana, Malta, which surround the fortifications of Valletta and form the capital city's outer defences. Construction of the lines began in 1636 and they were named after the military engineer who designed them, Pietro Paolo Floriani. The Floriana Lines were modified throughout the course of the 17th and 18th centuries, and they saw use during the French blockade of 1798–1800. Today, the fortifications are still largely intact but rather dilapidated and in need of restoration.
A curtain wall is a defensive wall between two towers (bastions) of a castle, fortress, or town.
A ditch in military engineering 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 North Bastion, formerly the Baluarte San Pablo was part of the fortifications of Gibraltar, in the north of the peninsula, protecting the town against attack from the mainland of Spain. The bastion was based on the older Giralda tower, built in 1309. The bastion, with a mole that extended into the Bay of Gibraltar to the west and a curtain wall stretching to the Rock of Gibraltar on its east, was a key element in the defenses of the peninsula. After the British took Gibraltar in 1704 they further strengthened these fortifications, flooding the land in front and turning the curtain wall into the Grand Battery.
In fortification architecture, a rampart is a length of bank 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 or masonry or a combination of the two.
The Santa Margherita Lines, also known as the Firenzuola Lines, are a line of fortifications in Cospicua, Malta. They were built in the 17th and 18th centuries to protect the land front defences of the cities of Birgu and Senglea. A second line of fortifications, known as the Cottonera Lines, was later built around the Santa Margherita Lines, while the city of Cospicua was founded in the 18th century within the Santa Margherita and Cottonera Lines.
The fortifications of Valletta are a series of defensive walls and other fortifications which surround the capital city of Valletta, Malta. The first fortification to be built was Fort Saint Elmo in 1552, but the fortifications of the city proper began to be built in 1566 when it was founded by Grand Master Jean de Valette. Modifications were made throughout the following centuries, with the last major addition being Fort Lascaris which was completed in 1856. Most of the fortifications remain largely intact today.
The fortifications of Mdina are a series of defensive walls which surround the former capital city of Mdina, Malta. 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.
A polygonal fort is a type of fortification originating in France in the late 18th century and fully developed in Germany in the first half of the 19th century. Unlike earlier forts, polygonal forts had no bastions, which had proved to be vulnerable. As part of ring fortresses, polygonal forts were generally arranged in a ring around the place they were intended to protect, so that each fort could support its neighbours. The concept of the polygonal fort proved to be adaptable to improvements in the artillery which might be used against them, and they continued to be built and rebuilt well into the 20th century.
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