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 . 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 . 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 . 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 . 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 . Carnot opposed the Bastion system . The elements of his system were : 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 . 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 ) . 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 sortie s from behind the wall up the countersloping glacis . Objections to Carnot ' s system . Objections to Carnot ' s system included that : 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 . In the same period the Russians used the walls in fortifying Warsaw . In Germany examples were built at Coblenz and Ulm . 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 . In 1823 a replica Carnot wall was constructed at Woolwich , Kent to test Carnot ' s theories . This wall was high and long . The tapering wall was thick at its base and thick at the top . A rampart of equal height with the wall was built in front of it to represent that of a real fort . 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 . Those conducting the experiments concluded that the wall could be severely damaged even if the besiegers ' gunners could not see it . 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 . 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 . 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 . Fergusson also commented that the 1824 Woolwich experiments , which had influenced subsequent fort design , had given " every possible advantage in favour of the attack " . 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 . 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 high with open - angled bastions . In 1857 a very similar fort was constructed at Shoreham along the coast from Littlehampton . The wall there included Caponier s , as also advocated by Carnot . Following the Royal Commission on the Defence of the United Kingdom of 1859 several forts with Carnot walls were built . These included : See also . Palmerston Forts