Carnot wall
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Carnot wall
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.[1] 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.[2][3][1] Their adoption was initially resisted by
the French themselves and by the British.[4][5]
The Carnot wall at Forte Altavilla, Ancona, Italy
Lazare Carnot and his system of fortification
Carnot was born in 1753. He became a military engineer at the age of
20. He became a politician during the French Revolution in 1789. He
was responsible for the organization of the campaigns of the French
Revolutionary Army, and later served under Napoleon. Carnot's "A
treatise on the defence of fortified places" was published in 1810 with
an English translation by Baron de Montalembert published in 1814.[6]
In this period the design of fortifications was based on the bastion
"trace" or ground-plan. This had originated in Italy in the 16th
century.[7]. From the late 17th century the model system of fortification
was considered to be that based on the bastion trace of Vauban, Louis
XIV's military engineer.[8]
Carnot opposed the Bastion system.[9]. The elements of his system
were:
• vertical fire from mortars;
• a countersloping glacis;[10]
• sorties by defenders;[11]
Lazare Carnot
• the "Carnot" wall and;
• separation of defence and attack.[1][12]
A conventional fort would have ramparts on which the cannon were mounted. The ramparts were surrounded by a
ditch with vertical, or near vertical, sides, called the scarp (inner wall) and counterscarp (outer wall). The outer side
of the ditch would have a glacis, a gently outwardly sloping earth bank at a slightly lower level than the ramparts.
The glacis would be topped by a parapet with a flat area called the "covered way" (because it was "covered" by fire
from defenders on the ramparts). This arrangement was intended to make it difficult for attackers to approach the fort
while allowing defenders to observe, and fire on, approaching besiegers at some distance from the fort.[13]
As against this method Carnot's system did away with the covered way and steep counterscarp and made the glacis
slope back into the ditch. (This is referred to as a countersloping glacis).[10]. He placed a loop-holed wall in the ditch
of the fortification. This had a chemin des rondes, or sentry path, to the rear allowing defenders to move along
behind the wall. As well as firing at attackers the defenders were able to make sorties from behind the wall up the
countersloping glacis.
Carnot wall
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Objections to Carnot's system
Objections to Carnot's system included that:
•
•
•
•
it required excessive manpower and firepower;[14]
the detached masonry wall itself would be vulnerable to artillery attack;[15][16]
sorties were of limited effectiveness as a defensive tactic;[17]
the effectiveness of vertical fire is exaggerated.[18]
Adoption of Carnot's ideas in continental Europe
The Austrians built impressive fortifications in the 1830s, using
Carnot's ideas, at Verona in Italy. These consisted of massive ramparts
with a Carnot wall at their foot.[19]. In the same period the Russians
used the walls in fortifying Warsaw.[19] In Germany examples were
built at Coblenz [20] and Ulm.[21]
San Bernardino Fort, Verona, Italy - showing the
ramparts and Carnot wall
The Woolwich Experiments
Whilst the Carnot wall was extensively
employed in fortifications in continental
Europe there was resistance to its use in
Britain, for the reasons stated above.[4]
In 1823 a replica Carnot wall was
constructed at Woolwich, Kent to test
Carnot's theories. This wall was 21 feet
(6.4 m) high and 22 feet (6.7 m) long. The
tapering wall was 7 feet (2.1 m) thick at its
Illustration of the replica Carnot Wall constructed at Woolwich in 1823 - showing
base and 6 feet (1.8 m) thick at the top.[22] A
the effect of bombardment.
rampart of equal height with the wall was
built in front of it to represent that of a real fort.[23] The idea was that the gunners would be unable to see the wall
itself when firing.
Experiments with this wall took place in August 1824. Their object was to test whether artillery at a distance could
breach the walls by firing at high angles.[22] Those conducting the experiments concluded that the wall could be
severely damaged even if the besiegers' gunners could not see it.[24] However it was objected that the Woolwich
experiments did not really prove what was claimed. The tests used far more artillery fire than would be likely to be
possible in a real siege.[25]
Carnot wall
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Later British Forts with a Carnot wall
The objectors did not hold sway indefinitely however and forts with
Carnot walls were eventually built in Britain. In his 1849 book James
Fergusson outlined the advantages of the Carnot wall, though without
wholly endorsing its use.[26] He said that such walls would be cheaper
to construct. They would last longer than the usual scarp wall with a
"mass of earth at its back always tending to overthrow it". In addition it
would be difficult to scale the wall as the besiegers would have to use
ladders to reach the top and the same ladders to descend the other side,
while all the time facing assault by defenders.[26] Fergusson also
The Carnot wall in the fort at Littlehampton
commented that the 1824 Woolwich experiments, which had
influenced subsequent fort design, had given "every possible advantage
in favour of the attack".[27] He argued that, even were a breach to be made in the wall, the defenders could easily
attack the besiegers, making an assault on the fort hazardous. His final point was that in any case the wall would be
hidden behind a rampart far higher, in relation to the height of the wall, than that at Woolwich, so that the enemy
artillery would be not able to significantly damage it.[27]
The first fort to be built in Britain with a Carnot wall was in 1854 at the mouth of the river Arun at Littlehampton in
West Sussex. This was 12 feet (3.7 m) high with open-angled bastions.[28] In 1857 a very similar fort was
constructed at Shoreham along the coast from Littlehampton. The wall there included Caponiers, as also advocated
by Carnot. [29]
Following the Royal Commission on the Defence of the United
Kingdom of 1859 several forts with Carnot walls were built. These
included:
• Sandown Barrack Battery, Isle of Wight
• Redcliff Battery, Isle of Wight
• Yaverland Battery, Isle of Wight
• Shotley Battery, Harwich, Essex
• Fort Wallington, Portsdown, Portsmouth, Hampshire
• Woodlands Fort, Plymouth, Devon
Yaverland Battery
References
[1] Saunders 1989, p. 155.
[2] Duffy 1975, p. 52.
[3] Douglas 1859, p. 103.
[4] Douglas 1859, p. 83.
[5] Saunders 1989, p. 158.
[6] Carnot 1814.
[7] Duffy 1975, p. 9
[8] Duffy 1975, p. 16.
[9] Saunders 1989, p. 156.
[10] Carnot 1814, p. 204.
[11] Carnot 1814, p. 197.
[12] Barrass 2011, p. .
[13] Duffy 1975, pp. 59-63.
[14] Douglas 1859, p. 81.
[15] Douglas 1859, p. 148.
[16] Lendy 1862, p. 453.
[17] Douglas 1859, p. 111.
Sandown Barrack Battery
Carnot wall
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
Lendy 1862, p. 449.
Hughes 1974, p. 171.
Douglas 1859, p. 125.
Hughes 1974, p. 169.
Douglas 1859, p. 96.
Douglas 1859, p. 97.
Douglas 1859, p. 99.
Lloyd 1887, p. 194.
Fergusson 1849, p. 54.
Fergusson 1849, p. 55.
Goodwin 1985, p. 36.
Goodwin 1985, p. 45.
Bibliography
Barras, Simon (2011). "An Introduction to Artillery Fortifcation" (http:/ / www. fsgfort. com/ uploads/ pdfs/ Public/
Introduction to Fortifications P.pdf). Fortress Study Group. Retrieved 10 January 2011.
Carnot, Lazare (1814). A treatise on the defence of fortified places: Written under the direction and published by
command of Buonaparte, for the instruction and guidance of the officers of the French Army. London: Printed for T.
Egerton.
Douglas, Sir Howard (1859). Observations on modern systems of fortification: including that proposed by M.
Carnot, and a comparison of the polygonal with the bastion system; to which are added, some reflections on
intrenched positions, and a tract on the naval, littoral, and internal defence of England. London: J. Murray.
Duffy, Christopher (1975). Fire & Stone: The Science of Fortress Warfare 1660-1860. (First ed.). Newton Abbot:
David & Charles.
Fergusson, James (1849). An essay on a proposed new system of fortification: with hints for its application to our
national defences. London: J. Weale.
Goodwin, John (1985-11-09). The Military Defence of West Sussex (1st ed.). Midhurst: Middleton Press.
ISBN 0906520231.
Hughes, Quentin (1974). Military Architecture. Beaufort Publishing. ISBN 1855120089.
Lendy, Auguste Frederic (1862). Treatise on fortification: or, Lectures delivered to officers reading for the staff.
London: W. Mitchell.
Lloyd, Ernest Marsh (1887). Vauban, Montalembert, Carnot: Engineer studies. London: Chapman and Hall.
Saunders, A D (1989). Fortress Britain: Artillery Fortification in the British Isles and Ireland. Liphook: Beaufort
Publishing. ISBN 1855120003.
Yule, Sir Henry (1851). Fortification for officers of the army and students of military history. London.
External links
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Victorian Forts and Artillery (http://www.victorianforts.co.uk/index.php) Retrieved 2012-01-15
The Palmerston Forts Society (http://www.palmerstonforts.org.uk/) Retrieved 2012-01-15
Shoreham Fort (http://www.shorehamfort.co.uk) Retrieved 2012-01-15
Woodlands Fort, Plymouth (http://www.subterraneanhistory.co.uk/2010/02/
being-important-naval-base-plymouth-was.html) Retrieved 2012-01-15
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Article Sources and Contributors
Article Sources and Contributors
Carnot wall Source: http://en.wikipedia.org/w/index.php?oldid=471737896 Contributors: Kinnerton
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File:Ancona - Forte Altavilla 1863.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Ancona_-_Forte_Altavilla_1863.jpg License: Creative Commons Attribution-Sharealike 3.0
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File:BastioniSanBernardinoAllaCarnot.jpg Source: http://en.wikipedia.org/w/index.php?title=File:BastioniSanBernardinoAllaCarnot.jpg License: unknown Contributors: Kinnerton
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