Bastion

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Drawing of a bastion Bastion (PSF).jpg
Drawing of a bastion

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. [1] 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.

Contents

Evolution

Some of the first polygonal bulwarks that would define the trace italienne were built at Rhodes between 1486 and 1497. Rhodos185.JPG
Some of the first polygonal bulwarks that would define the trace italienne were built at Rhodes between 1486 and 1497.

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. [3]

One of the semi-circular bastions at Deal Castle, a Device Fort on the south coast of England. Deal Castle - geograph.org.uk - 1406977.jpg
One of the semi-circular bastions at Deal Castle, a Device Fort on the south coast of England.

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. [3]

Aerial photograph of Neuf-Brisach, a fortress in use during the Napoleonic Wars. Neuf-Brisach 007 850.jpg
Aerial photograph of Neuf-Brisach, a fortress in use during the Napoleonic Wars.

These ideas were further developed and incorporated into the trace italienne forts by Sébastien Le Prestre de Vauban, [3] that remained in use during the Napoleonic Wars.

Effectiveness

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.

A bastion in the Komarno Fortress (Slovakia). Komarno - Castle.jpg
A bastion in the Komárno Fortress (Slovakia).

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. [4] 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. [5]

Types

Various kinds of bastions have been used throughout history.

See also

Notes

  1. Whitelaw 1846 , p. 444
  2. Nossov & Delf 2010, p. 26.
  3. 1 2 3 Hinds & Fitzgerald 1981, p. 1.
  4. Patterson 1985, pp. 7–10.
  5. Hyde 2007, pp. 50–54.
  6. 1 2 3 4 5 6 7 8 9 10 Chambers 1728, p. 90.

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