Brilliant officer and engineer of the Royal Corps of Engineers in the 18th century^{, the Chevalier} d'Arçon, a brilliant theoretician of the art of fortifications, but also a tactician and skilful warlord, remains however largely unknown. He was a defender of Vauban's legacy, and his ideas heralded the future Séré de Rivières system. Captain Roussel, a regular contributor to the Cahiers, gives us here a scholarly and enthusiastic biography of this officer-engineer.

A renowned poliorcete from the end of the 18th century playing a key ^role in the organization of the Republic's armies, the Chevalier d'Arçon remains a largely unknown theorist. The change in the art of warfare during the wars of the Revolution and the Empire overshadowed the study of fortifications, which was confined to "men of art", a trend reinforced by the definitive abandonment of the bastioned layout after 1873. Thus, only two engineering officers, Girod de Chantrans [1] and Rochas d'Aiglun [2] have devoted exhaustive biographical notes to d'Arçon. Let us also mention the work of two promoters of polygonal fortification, General de Blois [3] and Colonel Vauvilliers [4], both evoking the influence of his fulcrum theory. More recently, he is evoked in the studies of Anne Blanchard [5] and Hélène Vérin [6] relating to the royal corps of engineers, as well as in those of Jean-Marie Thiébaud and Gérard Tissot-Robe [7], but he is especially rediscovered as a follower of Bourcet for his contribution to cartography [8]. However, his theories on advanced works had a decisive influence on a generation of engineers embodied by Carnot [9], Gay de Vernon [10], Bousmard [11] and Chasseloup-Laubat [12]. Thus, Arçon's career and work require a renewed approach insofar as they offer a remarkable testimony to the mutations of engineering in the 18th century and its role in contemporary ^tactical controversy. Moreover, his theories tend to defend and safeguard the legacy of Vauban and Cormontaigne by demonstrating the compatibility of this strategic marker of absolutism with revolutionary ideology and the new system of warfare.

Jean Claude Eléonore Le Michaud, Lord of Arçon, was born on 18 November 1733. This son of a bisexual jurist, originally destined for the orders, very early on had the ambition to become a military engineer. In 1754, he was admitted to the Royal School of Engineering in Mézières, then was appointed lieutenant and received the title of ordinary engineer the following year. He joined a corps whose essence Carnot perfectly captured in his Éloge de Vauban [13], the "Jesuits ofthe army", devoid of troops, forced to an intellectual and corporate defence against the artillery and the geographers engineers. The department of fortifications then underwent a slow process of "militarisation" until the order of 31 December 1776 creating the royal corps of engineers [14]. Its missions were mainly limited to conducting sieges and then, in peacetime, to monitoring the fortifications and mapping the borders.

During the Seven Years' War, d'Arçon was assigned to "service in the field", first to the observation army on the coast of Brittany and then to Germany in 1760. He distinguished himself at the siege of Dillenburg, prepared the defense of Göttingen and participated in the operations of the two blockades of Kassel [15]. Promoted captain and engineer first class at the end of the hostilities, he is assigned to the "service des places", first in Sedan then in the castle of Joux. Now chief engineer, he is charged between 1774 and 1778 to continue the cartography of Provence and Dauphiné begun by Bourcet. Then, promoted to sub-brigadier of engineering, he undertook that of the eastern borders in the Jura and Vosges from 1779 to 1786 [16]. 16] This mission remains unfinished for lack of funds; however, it led d'Arçon to form avant-garde theories on the formation of the relief [17]. In spite of his junior rank, d'Arçon was frequently called upon by the directors of engineering to pronounce on the pertinence of new systems of fortifications based on the principle of direct flanking. Thus, in 1767, he rejected Boisforet's "tétragone" and the following year he published his first work "Letter from an engineer to one of his friends"18], refuting Trincano's nine systems,[19] in which he engaged in an imaginary dialogue between Vauban and Coehoorn, analysing the work and durability of the two masters. In 1774, invited by the Secretary of State for the Navy to present his views on the defence of Mauritius, he opposed the Marquis de Montalembert, leader of the "perpendicular system" [20]. 20] The latter obtained permission to publish his theories in 1776,[21] but d'Arçon did not begin to refute them until after his attacks on the works in the Cherbourg roadstead[22]. This intellectual duel lasted until 1793 when Montalembert launched a final attack against the bastioned system [23]. 23] Arçon's reply, while acknowledging the conservatism of the genius and the potential of Montalembert's "caponier system", shows that his reaction to the attack on the bastioned system was a success.The replica of Arçon, while acknowledging the conservatism of engineering and the potential of Montalembert's "caponiered system", shows that its bending based on exact premises had however led to erroneous conclusions, and proposes casemates of its design integrated into the bastioned line [24]. But this controversy represents only one facet of the general questioning of Vauban's legacy.

In the 1770s, d'Arçon published four pamphlets entitledAn engineer's thinking in response to a tactician25], then " Correspondance surl'art militaire"[26], "[26], "[27] and "[28].Reflections on the letter to a friend[26], "[27] and " Defence of a national war system"[28]in which he took the side of Mesnil-Durand against Guibert. The author of the Essaigénéral de tactique condemns strongholds imposing on states the maintenance of an expensive military apparatus and a siege war in which limited commitments are favoured to the detriment of the decisive battle. D'Arçon, who integrates the points of support as a component of the general system of the forces of the nation, evokes on the contrary the dissuasive virtues of a fortification in accordance with the national engineering. This spares the maintenance of manpower more useful to the economic development of France allowing it to consolidate its supremacy while preserving peace. In 1786, Choderlos de Laclos, who was in favour of Montalembert's theses, revived the controversy by criticizing Vauban's praise proposed in the Academy competition, arguing that the expert engineer in the fortification of the French army was a "master of the fortress".The engineer, an expert in the attack on the squares, proved incapable of innovation in defensive art, initiating, moreover, a vast program of fortifications that burdened the finances of the kingdom without any guarantee of security [29]. 29] Braving the censorship of the Marshal of Segur, d'Arçon responded by publishing his "... the fortifications of the kingdom".Considerations on the influence of Vauban's genius in the balance of power of the state"»[30]. 30] For the author, the dichotomy established between attack and defense of the squares is unfounded, they are two facets of the same art: a siege is nothing more than a fortification that progresses, supplied with troops and materials, against another surrounded. The impregnable fortification is a chimera; in short, art is always defeated by the superiority of numbers. Vauban standardized and brought to perfection principles that are still valid without significant progress in artillery equipment. He thus bequeathed the only permanent system of the "public force" allowing to maintain the "balance of forces" with the neighbouring powers. At the same time, the War Council suggests among various budgetary measures a redesign of the defensive system and publishes in 1788 a Collection of a few meticulous measures. moires on the too large number of strongholds that remained in France, presented as Extracts from the manuscripts of the late Marshal Vauban, where 99 places were offered for disarmament. Supported by Carnot[31], d'Arçon refutes these proposals in his "Military andPolitical Considerationson the Projected Reform ofa large number of our places of war" and his "Observations on thefragments of memoirs attributed to Marshal de Vauban on the question of fortified places" [32]. The engineer, relying on the War of Spanish Succession, shows that the squares of Alsace and Flanders, forming the squares of a strategic chessboard, are the most important places of the war.The engineer, relying on the War of the Spanish Succession, shows that the Alsace and Flanders squares, forming the squares of a strategic chessboard, served successively as safety positions, operations pivots and then as warehouses allowing Villars to prepare the recovery of Denain.

At that time, d'Arçon was considered one of the first engineers in Europe; paradoxically, this reputation was based on his role in the failure of the Great Siege of Gibraltar. In the summer of 1781, he was assigned to the operations of the siege at the request of the Earl of Aranda. As both a land assault and a naval bombardment of the British enclave were considered impossible, the engineer therefore submitted a plan for an attack combining a land assault from San Roque, the landing of an amphibious corps in the cove of Les Remedios and unsinkable and incombustible batteries [33].

33] These ten batteries, supported by gunboats, were to emboss themselves on two staggered lines and beat the works of the old breakwater. Approved, the attack project was entrusted to the Duke of Crillon despite his reservations. The land phase began in mid-August 1782 with the execution of a flying sapper and a great parallel. At the beginning of September, the advanced batteries were unmasked and applied reverse and enfilade fire on the old breakwater. But Crillon precipitated the assault after the arrival of the covering squadron. On 13 September, the batteries sailed; three of them missed their embossing and the others grounded out of reach on sandbanks. By the end of the day, the fire was out of control on the only two batteries involved. Crillon cancelled the towing operations and ordered the destruction of the prams. This failure dealt a decisive blow to the morale of the besiegers. In spite of the gratifications received on his return to France in October 1782, d'Arçon was deeply disappointed. Initially censored by the Secretary of State for War, he had a justification memorandum printed in Spain[34], followed by the Privy War Council. on the event in Gibraltar [35] where he included his experiments on the resistance of oak to reddened cannonballs [36].

A freemason and a winner of the "new ideas", d'Arçon was elected deputy of the nobility of Pontarlier at the Estates General and then commander of the National Guard of Besançon in 1790. Promoted marshal de camp and appointed Inspector General of Fortifications in 1791, he assisted the Count of Narbonne in his tour of inspection of the border places and collaborated in the drafting of the first report to the Nation on its defence tool [37]. 37] Called to sit on the fortification committee by Duportail, he was in charge of a reconnaissance of the border of the Alps in 1792, then of the country of Porrentruy the following year. In February 1793, d'Arçon was assigned to the army of the North at the request of Beurnonville [38]. The crux of the operation planned by Dumouriez consisted in piercing the triangle formed by Berg-op-Zoom, Breda, Geertruidenberg and Willemstad, places covered by floods, equipped with numerous garrisons, powerful artillery and well supplied [39]. In charge of the command of the division of the right wing, d'Arçon led a series of lightning sieges with only small losses: Breda, invested on February 15, capitulates on February 27 after four days of bombardment; the works detached from Geertruidenberg are removed by a series of blows of hand from March 1 and the garrison capitulates after four days of bombardment.Appointed Major General on March 2, 1793, but suffering from universal rheumatism and worried about the deterioration of the political climate, he requested that he be placed on standby. From 1792 onwards, d'Arçon was suspected of counter-revolutionary activities; charged with reworking Besançon's defences, he was accused of working to bring about the fall of the town. Charles of Hesse[40] demands his dismissal and has him condemned by the district court despite the publication of an address of the engineer to his fellow citizens[41]. 41] Once again a suspect after Dumouriez's defection, Carnot intervened in his favor[42] and associated him with the War Committee, whose reports he communicated to the Committee of Public Salvation. In particular, he drew up the campaign plan for January 1794 with Laffite-Clavé and Rivière [43]. In 1796, d'Arçon retired to Voray where he devoted himself to writing a treatise entitled De la guerre conservatrice des empires, the manuscript of which remains unpublished. The Chevalier d'Arçon died on 1 July 1800 at the Château de la Tuilerie in Auteuil, when he had just been appointed to the Conservative Senate.

In 1795, Carnot entrusted d'Arçon the inaugural lesson of the fortification course at the École Centrale des travaux publics [44]. 44] This synthesis of his entire theoretical work was immediately published by order of the government under the title of Considérations militaires et politiques sur les fortifications [45]. Aware of the role of public opinion in the conduct of operations, the author pleads for inspiring "enlightened confidence" in its defences and revealing the real potential of fortifications. The book first analyses the general principles of fortification, then the rules guiding the distribution of works at the borders; finally, the author considers the future of fortifications while remaining faithful to the "indelible bases" laid down by Vauban. He thus offers a didactic treatise of a predictive nature in which he defends a defensive policy designed to ensure lasting peace and conceptualizes the sanctuarization of a fortress state that has reached its territorial optimum.

Actor in the transition from the war of princes to the war of peoples, fromArçon has the intuition that the "revolutionary crisis" favours the emergence of a dual nature of war. He announces that the new form of war characterised by the systematic recourse to the "mass of the people" and the "extraordinary resources of devastation" presents a major danger for France insofar as the nation will not be able to prolong indefinitely the effort made during the campaigns of the first coalition. The state of permanent belligerence will thus lead to the advent of a "military government", to the decadence of the "military spirit" and France will gradually be reduced to an "absolute defensive state". D'Arçon thus asserted himself as a theorist of limited warfare and of a bipolar strategy to avoid a defeat that he saw as inevitable in the face of "combined military Europe".

The theories defended by d'Arçon, which integrate the principles of the "European Union", are based on the principles of the "European Union as a whole" and the "European Union as a whole".The theories defended by d'Arçon, incorporating the principles of economy of means and forces, are based on the postulate that the "general conservative provisions" of the nation and the defence of the places obey similar laws. Whatever the value of a defensive organisation, its "invulnerability" rests on the combination of "material inertia" and "material efficiency". and "mobility of active means" that help transform defensive squares and curtains into "active living masses". Thus, if the power of a State emanates from a "regular military force incorporated into the Nation", fortifications are the inescapable "accessories" of the "warrior genius". They establish a balance of deterrent forces with the border powers and form at the borders "insensitive boulevards" to internal political crises, offering the "unity of intent" that contributes to the rallying of forces. The author thus sees in genius the "weapon par excellence of freedom", intended to regenerate the "freedom of the people".The author thus sees the engineer as the "weapon par excellence of freedom", intended to regenerate the nation's military spirit and to promote the establishment of a model of citizen army in which the infantry will enjoy a decisive preponderance. At the operative and tactical levels, the author subordinates freedom of action and initiative to the support of fortified points and their frequency. He thus refutes the effectiveness of a system of "open warfare", preferring "planned and combined operations" based on the concept of "militarized fortifications". In the tradition of Vauban, d'Arçon proposed a strategy of attrition and risk control aimed at optimising an active defence while limiting the scope of possible setbacks. He conceived the squares as centres of moral forces, attractive poles around which the "dangerous mobility of the offensive" gravitates, serving in turn as safety points, large depots and hubs of operations depending on the outcome of the fighting. The fortifications will thus channel the recklessness typical of national engineering, reserving troops for decisive action. Thus the "conservative industry" will preserve the balance of the initiative while making it possible to prepare the means to break it in favour of the state under attack.

The value of these militarized fortifications must correspond to a framework of "three effective and contiguous lines". In the first line, extended squares requiring the deployment of the largest siege aircraft, then "depot squares" in the second line and, in the third line, "resource squares", armed only when entering the field. The intervals between the squares would be defined in such a way as to threaten enemy communications. The system would be supplemented by waiting and observation positions at the level of the second line, entrenched camps allowing the armies to move offensively into the forward line. This model defensive curtain would have to be adapted to support the relief, hydrography, etc.. The position, the nature of the works and the strength of their garrisons will be determined in accordance with the spirit of the government of the frontier powers, the forces at their disposal, the lines of operation, the nature of the works and the strength of their garrisons.The position, the nature of the works and the strength of their garrisons shall be determined in accordance with the spirit of the government of the frontier powers, the forces at their disposal, the lines of operation, the potential rations, the number and nature of communications, the local ratio of attack and defence, the nature of the soil, the climate and, finally, the time necessary for the execution of "offensive returns". Concerning the base of the squares and the bastioned layout, d'Arçon perpetuated the principles of scrolling, flanking, staggering in depth and staggering of the lights standardised by Vauban and Cormontaigne. It favours "masking locations" facilitating logistical manoeuvring and criticizes excessive use of water manoeuvring. Finally, he urged the French armies to revive the art of attacking and defending the squares that had established their tactical superiority in the 17th century. He thus advocates the adoption of a joint combat in which manoeuvres will be linked to defensive organisations in order to facilitate entry into enemy territory and the safety of returns.

The militarised fortifications will allow the implementation of aThe militarised fortifications will allow the implementation of a "covered defence" and then an "attacking defence" continuous over time. The "advanced buttresses" of the first line will make it possible to identify the aggressor's campaign objectives, will force him to abandon active operations and will cancel out the initial numerical inferiority of the defender. The defending army, from its prepared position in the second line, will benefit from assured communications, moral ascendancy and preserve its freedom of action. It will seize the initiative when it has the numerical superiority that will allow it to impose the battle while enjoying an assured retreat by relying on the positions adjacent to the second or third line positions. D'Arçon expected that the aggressor would be forced to conduct several campaigns to achieve a significant breakthrough in a frontier defended by militarized fortifications; he would then have exhausted his offensive potential and his communications would be threatened by the positions on his flanks. Militarized fortifications forming bases of operations will also lend themselves to the "offensive movements" of the "positive attack" by allowing the formation of diversions or large detachments threatening enemy communications and base of operations. Beyond a march into enemy territory, the author recommends staking out communications with strong points of support and supporting "forward heads" with "positions of the moment" occupying strong positions to cover "central observation positions". These "points of strength" should be distributed in such a way as to manoeuvre in their intervals, cover communications and prepare for the establishment of safe quarters. Finally, on the particular point of defending maritime borders and overseas possessions, it recommends that priority be given to vital civilian and military port infrastructure by recommending a combination of fortresses, coastal batteries, high seas vessel squadrons and maritime patrols.

The author devotes his final chapters to the future of fortifications and addresses the problem posed by advances in artillery. He proposes autonomous works intended to occupy the "distant and not very distant outsides" of the safety enclosure where they serve as pivots in the "war of assaults" led by the garrison of the place. A masonry illustration of the principle of active defence, the lunettes raised in the extensions of the bastions and half-moons acculturate Montalembert's theses to the line bastioned layout and perfect the principle of staggering by optimising the use of "covering masses" and "reserved fires prepared under cover". These works include

• An entrenchment of a triangular terraced rampart, the throat of which is beaten by the fires of the square. It forms "masses of glacis" entirely passing through the "means of organization"; open to the gorge and controlled by the low lights of the parapets, it is preceded by a ditch whose scarp and counterscarp are covered.
• A "platform rider", formed by:
  • A two-sided and two-flanked median with infantry barbet firing posts; it is closed off at the throat by a curtain with a postern and equipped with firing battlements.
  • An "external casemate" placed in the capital at the level of the median level prefiguring the shelter crosspiece. This guardhouse consists of a bomb-proof vaulted shelter covered by a terraced massif. It takes part in the progress of the work and protects the platform from enfilade or sash fire while constantly holding the garrison in defence.
  • A circular masonry tower-reduction protrudes from the gorge of the terre-plein and conceals the views and artillery of the attacker. This defensive barracks has two bomb-proof vaulted levels and is covered with a demountable roof. Its floor is equipped with an advanced fire plan for small arms.
  • A "backfiring casemate" integrated into the counterscarp at the salient of the entrenchment, prefiguring the double counterscarp box. Equipped with firing battlements, it is intended for the flanking of the ditch and allows the structure to support itself without the protection of the works behind.
  • Furtive communications" formed by a service gallery linking the backfires casemate, the cross-rail, the tower-reduction, and even the path-covered glacis of the square.
  • The "miners' gun emplacements" formed by masonry counter-mining galleries for the operation of the "underground lights"; they are located at the level of the reduction tower, the service gallery and the backfiring casemate.

The Chevalier d'Arçon appears to be one of the most brilliant military engineers of his generation. A prolific author, his theories announcing the Séré de Rivières system were the spearhead of the defence of engineering expertise in the second half of the 18th century. His thought, which was part of the rationalism of the Enlightenment, went beyond the simple framework of poliorcetics by seeking to isolate the causes of the fall of nations. He thus asserted himself as a strategist of dissuasion by basing his thinking on the impact of scientific progress. Defender of the notion of territorial optimum, he finally contributes to forging a new image of Vauban, that of a visionary "citizen warrior".

^[1]Girod de Chantrans (Justin), Notice sur la vie et les ouvrages du général d'Arçon, Besançon, Daclin, an IX [1801].

^[2]Rochas d'Aiglun (Albert de), "...D'Arçon military engineer. His life and writings"Paris, J. Dumaine, 1867.

3] Blois de la Calende (Étienne Gabriel de), "....Fortification in the presence of the new artillery", 2 vols., Paris, Dumaine, 1865.

^[4] Vauvilliers (Louis-Henri-Chrétien),".Tests on new military considerations"Paris, Gaultier-Laguionie, 1843.

^[5]Blanchard (Anne), Les ingénieurs du roy de Louis XIV à Louis XV. Étude du Corps des Fortifications, Montpellier, Université Montpellier III-Paul Valéry, 1979.

^[6]Vérin (Hélène), "Glory of Engineers: technical intelligence from the 16th to the ^18th century"Paris, Albin-Michel, 1993.

7] Thiébaut (Jean-Marie) and Tissot-Robe (Gérard), "[7 ] Thiébaut (Jean-Marie) and Tissot-Robe (Gérard), ".Elisabeth Le Michaud d'Arçon,... Mistress of Napoleon"Cabédita, 2006; Choffat (Thierry), Thiébaut (Jean-Marie) and Tissot-Robe (Gérard),".Napoleon's Comtois. One hundred destinies in the service of the Empire"Cabédita, 2006.

8] Pelletier (Monique), ".From Cassini de Thury to Le Michaud d'Arçon: the French military and triangulation in the second half of the 18th century"Royal Library of Belgium, 2006.

[9 ] Carnot (Lazare), "[9 ] Carnot (Lazare), " " .Defending the strongholds. Compound work for the instruction of the students of the Corps of Engineers."Paris, Courcier, 1810.

10] Gay de Vernon (Simon-François), "Traité élémentaire d'art militaire et de fortification: à l'usage des élèves de l'École polytechnique, et des élèves des écoles militaires", 2 vols, Paris, Allais, 1805.

11] Bousmard de Chantereine (Henri Jean-Baptiste de), ".General Essay on Fortification and the Attack and Defence of Squares", [ ...], 4 volumes, Berlin, George Decker, 1797-1803.

12] Chasseloup-Laubat (François, count of), "....Tests on some parts of the artillery and fortifications"Milan, J.J. Destefanis, 1811.

^[13] Carnot (Lazarus), "...In praise of Marshal de Vauban", Dijon and Paris, A. Jombert Jeune, 1784.

^[14] Memory of the body of the genius, 1776 [ ...], Municipal Library of Besançon, Ms. 491, 11°, 135 sheets.

^[15] Relation du siège de Cassel, Bibliothèque municipale de Besançon, Ms. 491, 1°.

^[16] Corvisier de Villèle (Marie-Anne) and Ponnou (Claude), La France vuepar les militaires. Catalogue des cartes de Frances du Dépôt de la Guerre, Château de Vincennes, 2001, t.1.

^[17] Essay of a theory on the formation and context of mountains, Bibliothèque municipale de Besançon, Ms. 491, 9°, 14 leaves.

^[18] Le Michaud d'Arçon (Jean Claude Éléonore),".Letter from an engineer to a friend of his"Amsterdam-Paris, Le Breton, 1768, in-12°, 219 pages.

^[19] Trincano (Didier Grégoire), "".Elements of fortifications, attack and defense of the squares; containing the systems of the most famous authors, nine systems of the author, analysis and comparison of all these systems Paris-Versailles, J.B.G. Musier et Lefevre, 1768.

^[20] Montalembert denounces the weakness of the flanking of a bastioned enclosure, its lack of depth, the proximity of the works to the habitat as well as the dispersal and vulnerability of the artillery on the bastioned earthworks. According to Montalembert, the bastioned route, which was designed for close defence, was overtaken by the progress of the artillery: the artillery must now form the basis of the defence in order to halt the progress of the attacker and prevent sieges in accordance with the rules. Montalembert simplified the layout to enclose the cities in a polygon at right angles reducing the directions of potential attacks. This continuous fortification forming an entrenched camp is supplemented by an external line of defense consisting of polygonal belt forts concentrating the majority of the means of defense; they are presented as vast casemated batteries.They are presented as vast casemated and ventilated batteries with several levels of fire offering a flanking perpendicular to the line of fire so as to deploy artillery outnumbering that of the besieger and provide mutual support of the works.

^[21] Montalembert (Marc-René de), ".The Fortification perpendicular, or attempt in several ways to fortify the straight line, the triangle, the square and all polygons, regardless of the extent of their sides, by giving their defence a perpendicular direction"Paris, Philippe-Denys Pierre, 1776-1784.

^[22] Montalembert (Marc-René de), Supplement to volume five of the Perpendicular Fortifications, containing new evidence of the great superiority of the angular system over the bastioned system. One joined there I° a supplement relating to the needle mounts suitable to mount the artillery of the ships; II° a supplement to chapter IXème of the fifth volume, which treats of the ^various methods to be employed for the defense of a roadstead, 1786.

^[23] Montalembert (Marc-René, Marquis de), "....Defensive Art superior to the offensive, or Perpendicular Fortification, containing new evidence of the great superiority of the system.the angular system over the bastioned system, various memoirs with an addition to the theory of embrasures, given in chapter five of the second volume."Paris, Firmin Didot, 1793.

^[24] Le Michaud d'Arçon (Jean Claude Éléonore),".Des fortifications et des relations générales de la guerre de siège, to serve as an answer to Marc-René Montalembert's last work; by citizen Michaud, Inspector of Fortifications"Paris, Magimel, Year II [1794].

^[25] Le Michaud d'Arçon (Jean Claude Éléonore), " Réflexion d'uningénieur en réponse à un tacticien " , Amsterdam, s.n., 1773.

^[26] Le Michaud d'Arçon (Jean Claude Éléonore)," Le Michaud d'Arçon (Jean Claude Éléonore),".Correspondence on the art of war between a dragoon colonel and an infantry captain"Bouillon-Besançon, n.s., 1774.

^[27] Le Michaud d'Arçon (Jean Claude Éléonore), "....Reflections on the "Letter to a Friend", by the author of "Correspondence on the Art of War""s.l., s.n., 1775.

^[28] Le Michaud d'Arçon (Jean Claude Éléonore), "Défense d'un système deguerre national, ou analyse raisonnée d'un ouvrage intitulé: réfutation complète du système de M. de Mesnil-Durand," Amsterdam, 1779.

^{[29] «}Letter to Messrs. de l'Académie françoise, on the praise of M. le maréchal de Vauban, proposed as the subject of the eloquence prize for the year 1787"by P.-A.-F. Choderlos de Laclos, artillery captain of the Academy of La Rochelle, Paris-Amsterdam, Durand nephew, 1786.

^[30] Le Michaud d'Arçon (Jean Claude Éléonore), "Considerations on the influence of Vauban's genius in the balance of power of the state", in-8°, Strasbourg, s.n., 1786.

^[31] Carnot (Lazarus), "Memorandumpresented to the War Council on the subject of strongholds to be demolished or abandoned, or Examination of this question: Is it advantageous to the King of France that there should be strongholds on the borders of his States? Paris, Barois l'Aîné, 1789 .

^[32] In his writings, D'Arçon denounced the specious argumentation of the War Council, whose Collection is essentially made up of apocryphal writings. Concerning the authentic passages, he emphasizes their conjunctural character. On the other hand, the Council neglects the writings of 1705 and 1706, in which Vauban proposes for the first time a classification of the places while claiming the fortification of Paris, Lyon, Marseille, etc.

^[33] Ten ships were armed in Cadiz and then Algeciras between May and September 1782 in batteries with one or two decks, with the addition of a bomb-proof roof of holm oak covered with armouring of ropes, sacks and ox skins. D'Arçon worked to prevent fires caused by reddened cannonballs by removing fuel and oxidant: the apparatus is reduced to a minimum, a pumping system ensures a continuous flow of water saturating the structures exposed to fire, and careful caulking reduces air circulation. Served by 5,260 pragmatists, these batteries line up 142 fire hydrants. At the beginning of September, only three batteries were completed; tests revealed caulking defects and the reconnaissance and mooring buoys, as well as the emergency anchors and grelins intended for retirement, were not ready.

^[34] Le Michaud d'Arçon (Jean Claude Éléonore), ".Memoirs for use in the history of the siege of Gibraltar, by the author of the floating batteries"in-8°, Cadiz, Hernill frères libraires, 1783.

^[35] Le Michaud d'Arçon (Jean Claude Éléonore), "Conseil de guerre privé sur l'événement de Gibraltar en 1782 pour servir d'exercice sur l'art des sièges", widow Philippe Gaultier, 1785.

^[36] "History of the Royal Academy of Sciences. Year M.DCCLXXXIV. Avec les Mémoires de Mathématiques et de Physique pour la même année, tirés des registres de cette Académie", Paris, Imprimerie Royale, 1787, p. 18.

^[37] Narbonne-Lara (Louis-Marie, comte), "Discours duMinistre de la Guerre, sur l'état actuel des frontières et les dispositions de l'armée.Du 11 janvier 1792", in Collection générale des Décrets rendus par l'Assemblée nationale, Paris, Baudouin, 1792, vol. 25, pp. 40-65.

^[38] Aulard (François Alphonse) (ed.), Recueil des actes du Comité de Salut Public with the official correspondence of the representatives on mission and the register of the provisional executive council, Paris, Imprimerie Nationale, 1911, t. II, pp. 49, 64-66, 73-74.

^[39] Dumouriez (Charles-François du Périer), "Mémoiresdu général Dumouriez, écrits par lui-même", Frankfurt and Leipzig, 1794, pp. 1-47.

^[40] Chuquet (Arthur), "A Jacobin prince. Charles of Hesse or General Marat"Paris, Albert Fontemoing, 1906, pp. 180-201.

^[41] Le Michaud d'Arçon (Jean Claude Éléonore),".Address of Camp Marshal Darçon, to his fellow citizens of the Doubs department. From the French army to the orders of General Montesquiou, on October 6, 1792, the Ist of the French Republic", Besançon, Simard printing house, 1792.

^[42]Carnot (Hyppolite),".Memoirs on Carnot by his son"Paris, Pagnerre, 1861, t.1, pp. 126-154 and 425-426.

^[43] Michel (André) ed.Unpublished correspondence between Malet du Pan and the Viennese court (1794-1798), published according to manuscripts in the Vienna archives."Paris, Plon, Nourrit et Cie,¹⁸⁸⁴, vol. I, p. 77, vol. II, p. 44; The Manuscripts of J.B. Fortescue, preserved at Dropmore, Vol. II, bulletin n°16, p. 547.

44] Journal de l'École Centrale des travaux publics, 1st issue, Year III. Archives de l'École polytechnique, X 2 b 329.

45] Le Michaud d'Arçon (Jean Claude Éléonore), "Considérations militaires etpolitiques sur les fortifications, by Cen Michaud (Darçon), former Major^General and Inspector of Fortifications. Imprimé par ordre du Gouvernement", Paris, Imprimerie De la République, an III [1795].

Captain Roussel is a contract officer, historian, currently professor of history at the Military Schools of Saint-Cyr-Coëtquidan. He previously held the position of conservation assistant in the artillery and emblems department of the Musée de l'Armée in Paris, then professor of history-geography at the École nationale des sous-officiers d'active. He holds a DEA from the University of Paris IV Sorbonne "L'art opératif dans l'œuvre d'Antoine-Henri Jomini, fondements et héritages", (directed by Olivier Chaline), and is a doctoral student at the same university "Aux fondements de l'art opératif: Antoine-Henri Jomini and the Seven Years War, from historical practice to strategic theory", (still under the direction of Olivier Chaline).