Chapter 13: permanent fortifications.—Historical Notice of the progress of this Art.—Description of the several parts of a Fortress, and the various Methods of fortifying a position
Fortification is defined,--the art of disposing the ground in such a manner as to enable a small number of troops to resist a larger army the longest time possible. If the work be placed in a position of much importance, and its materials be of a durable character, it is called permanent; if otherwise, it receives the appellation of field, or temporary. Field-works are properly confined to operations of a single campaign, and are used to strengthen positions which are to be occupied only for a short period. Generally these works are of earth, thrown up by the troops in a single day. They are intimately connected with a system of permanent fortifications, but from the facility of their construction, no provision need be made for them before the actual breaking out of war. Indeed, they could not well be built before hostilities commenced, as their locality in each case must be determined by the position of the hostile forces.Having already described the general influence of permanent fortifications as a means of national defence, we shall here speak merely of the principles of their construction. It is not proposed to enter into any technical discussion of matters that especially belong to the instruction of the engineer, but merely to give the nomenclature and use of the more important parts of a military work; in a word, such general information as should belong to officers of every grade and corps of an army. [328]
The first species of fortification among the ancients was of course very simple, consisting merely of an earthen mound, or palisades. A wall was afterwards used, and a ditch was then added to the wall. It was found that a straight wall could be easily breached by the enemy's battering-rams; to remedy this evil, towers were built at short intervals from each other, forming a broken line of salient and re-entering parts. These towers or salient points gradually assumed a shape approximating to the modern bastion.
After the invention of gunpowder and the application of cannon to the attack and defence of places, it became necessary to arrange earthen ramparts behind the thin walls of the ancient works, for the reception of the new artillery. Moreover these walls were soon found inadequate to resist the missiles of the besiegers, and it became necessary to replace them by parapets of earth. I. order to cover the retaining walls of these parapets from the besieging batteries, it was also found to be necessary to lower these walls as much as possible, and to raise the counterscarps. The traces or plans of the works, however, received no material change till about the close of the fifteenth century.
It is not known who first changed the ancient towers into bastions. Some attribute it to an Italian, and with considerable show of reason, for a bastion was built at Turin as early as 1461. Achmet Pacha, it is said, fortified Otranto in this way, in 1480, but whether the system was previously known among the Turks cannot be determined. Others attribute the invention to Ziska, the celebrated leader of the Hussites. It is most probable that the transition from the tower to the bastion was a very gradual one, and that the change was perfected in several countries at about the same time.
Fortifications, like other arts and sciences, greatly [329] flourished in Italy under the Medicis, and that country furnished Europe with its most skilful engineers. Catharine of Medicis introduced into France many of her countrymen, distinguished in this profession; among these, may be named Bellamat, Bephano, Costritio, Relogio, Vorganno, the two Marini, Campi, and Hieronimo, who built several important places and directed the sieges of others. These able foreigners were rivalled by some distinguished French engineers, who laid the foundation of the “corps du Genie,” which has since become a school of military instruction for the world. Among the early French engineers may be distinguished Lafontaine Do Serre, Feuquieres, and St. Remy. Pedro Navarro had been appointed a member of this corps, but his attention was more specially directed to mining, and we do not learn that he distinguished himself in the construction of any fortification.
In Germany, in the beginning of the sixteenth century, Albert Durer distinguished himself as a writer on fortification; his book is remarkable as containing the germs of many of the improvements which were made by those who followed him. This is the more to be wondered at as he was not a professed engineer. After him followed Spekel, a native of Strasburg, who died in 1589. His writings are valuable as showing the state of the art at that time, and the changes which he himself introduced. He was an engineer of much practical knowledge and experience, having assisted at the sieges of Malta, Golletta, Vienna, Jula, Nicosia, Famagusta, &c.
The first French engineer who wrote on fortification was Errard de Bar-le-Duc, who published near the close of the sixteenth century. As an engineer, he was rivalled by Chatillon, a man of distinguished merit. Errard fortified Amiens, built a part of the castle of Sedan, and a portion of the defences of Calais. Under the reign of [330] Louis XIII. Desnoyers, Deville, Pagan, and Fabre were greatly distinguished Deville published in 1628. He was a man of much learning and experience; but he is said to have adopted, both in his theory and practice, the principles of the Italian school, with most of its errors. Pagan began his military career while young, and became marechal de champ at the age of 38, when, having the misfortune to become blind, he was compelled to relinquish his brilliant hopes. He was the ablest engineer of his age, and was also greatly distinguished in other branches of science In his plans he inclined to the Dutch rather than the Italian school of fortification. He published in 1645.
At the close of the sixteenth century, the Dutch had bee forced to resort to military defences to protect themselves against the aggressions of the Spaniards. As the Dutch were inferior in other military means, fortification became one of tie vital resources of the country. Their works, however, throw up in much haste, were in many respects defective, although well adapted to the exigencies of the time. Freytag, their principal engineer, wrote in 1630. Some of his improvements were introduced into France by Pagan. He was preceded by Marolois, (a cotemporary of Pagan,) who published in 1613.
In Germany, Rimpler, a Saxon, wrote on fortification in 1671. He was a man of great experience, having served at the sieges of Candia, Phillipsburg, Bonn, Riga, Bremen, Dansburg, Bommeln, &c. He fell at the siege of Vienna in 1683. His writings are said to contain the groundwork of Montalembert's system.
In Italy, after the time of Tartaglia, Marchi, Campi, &c., we find no great improvement in this art. Several Italians, however, distinguished themselves as engineers under the Spaniards. The fortifications of Badajos are a good example of the state of the art in Italy and Spain at [331] that epoch. The citadel of Antwerp, built by two Italian engineers, Pacciotti and Cerbelloni, in 1568, has become celebrated for the siege it sustained in 1832.
The age of Louis XIV. effected a great revolution in the art of fortification, and carried it to such a degree of perfection, that it has since received but slight improvement. The years 1633 and 1634 are interesting dates in the history of this art, as having given birth respectively to Vauban and Coehorn. The former was chief engineer of France under Louis XIV., and the latter held a corresponding position under the Dutch republic. Coehorn's ideas upon fortification are conceived with an especial view to the marshy soil of his own country, and, although well suited to the object in view, are consequently of less general application than those of his more distinguished cotemporary and rival. The best specimens of his mode of construction that exist at the present day, are the fortresses of Manheim, Bergen-op-Zoom, Nimiguen, and Breda.
Coehorn was followed in Holland by Landsberg, an able and practical engineer, who to much reading added extensive experience, having himself served at sixteen sieges. His system was in many respects peculiar, both in trace and relief; it dispensed with the glacis, and all revertments of masonry. His plans could be applied only to marshy soils. The first edition of his work was published in 1685.
But the career of Vauban forms the most marked and prominent era in the history of fortification; it constitutes the connecting link between the rude sketches of the earlier engineers, and the well-established form which the art has since assumed. In his earlier works we find many of the errors of his predecessors; but a gradual change seems to have been wrought in his mind by reflection and experience, and these faults were soon remedied and a [332] new and distinct system developed. Vauban has left no treatise upon his favorite art, and his ideas upon fortification have been deduced from his constructions, and from detached memoirs left among his papers. The nature of his labors, and the extent of his activity and industry, may be imagined from the fact that he fought one hundred. and forty battles, conducted fifty-eight sieges, and built or repaired three hundred fortifications. His memoirs, found among his manuscript papers, on various military and political subjects, are numerous, and highly praised even at the present day. But his beautiful and numerous constructions, both of a civil and military character, are real monuments to his genius. The best illustrations of his principles of fortification occur at Lille, Strasbourg, Landau, Givet, and Neuf-Brisack. His writings on mines, and the attack and defence of places, are, by the profession, regarded as classic. His improvements in the existing method of attack gave great superiority to the arms of his countrymen, and even enabled him to besiege and capture his rival Coehorn, in his own works. He died in 1707, and was soon succeeded by Cormontaigne.
The latter did not attempt the introduction of any new system, but limited himself to improving and perfecting the plans of his illustrious predecessors. His improvements, however, were both extensive and judicious, and are sufficient to entitle him to the place he holds as one of the ablest military engineers the world has ever produced. His works on the subject of fortification, besides being elegantly written, contain the most valuable information of any works we have. His most admired constructions are to be found at Metz, Thionville, and Bitche. The beautiful crown works of Billecroix, at Metz, are perfect models of their kind. Cormontaigne died in 1750.
Cotemporary with him were Sturin and Glasser. The former deviated but slightly from the systems of his predecessors, [333] but the latter invented several ingenious improvements which gave him great reputation.
Next follows Rosard, a Bavarian engineer; and Frederick Augustus, king of Poland, who devoted himself particularly to this art. The former casemated only the flanks of his works, but the latter introduced casemate fire more extensively than any one who had preceded him.
In France, Belidor and De Filey published about the middle of the last century. They were both able engineers but their systems were inferior to that of Cormontaigne.
In 1767 De la Chiche introduced a system of fortification in many respects original. He raised his covered ways so as to conceal all his masonry, and casemated a great portion of his enceinte. For exterior defence, he employed direct fire from his barbettes, and curvated fire from his casemates; the direct fire of the latter secured his ditches.
Next to De la Chiche follows Montalembort, who published in 1776. He was a man of much experience and considerable originality, but of no great ability as an engineer. Most of his ideas were derived from De la Chiche and the German school of Rimpler. His plans have generally been rejected by his own countrymen, but they still have advocates among the Germans.
General Virgin, a distinguished Swedish engineer wrote in 1781. His idea of strongly fortifying the smaller towns to the comparative neglect of the larger cities, constitutes one of the principal novelties in his system.
In 1794, Reveroni devised a system in which the casemates of Montalembert were employed, but his guns were so arranged as to be employed in barbette while the besiegers were at a distance, and afterwards to be used for casemated fire. The casemate gun-carriage, which formed a part of his invention, was ingenious, but never much employed in practice. [334]
Bousmard, a French emigrant, published in 1799. He adopted the general trace of Vauban, but introduced modifications in the details essentially different from those of Cormontaigne. Some of these modifications are very valuable improvements, while others are of a more character. Bousmard is, on the whole, a very able writer, and his works should be found in the library of every military engineer.
Carnot's celebrated treatise was published in 1810. He was evidently a man of genius, and during his career at the head of the War Department of France, numerous and very important improvements were made in the several branches of the military art, and especially in strategy. His work on fortification exhibits much originality and genius, but it is doubtful whether it has very much contributed to the improvement of this art. His ideas have been very severely, and rather unfairly criticized by the English, and particularly by Sir Howard Douglas.
Chasseloup de Laubat early distinguished himself as an engineer of much capacity and talent. He followed Napoleon in nearly all his campaigns, and conducted many of his sieges. He remodelled the fortifications of Northern Italy and of the Lower Rhine. He published in 1811. The improvements which he introduced are numerous and valuable, and he probably contributed more to advance his art, and to restore the equilibrium between attack and defence, than any other engineer since Cormontaigne. After the fall of Napoleon and the partition of his empire, the allies mutilated or destroyed the construction of Chasseloup, so that, it is believed, no perfect specimen of his system remains.
The cotemporaries of Chasseloup were mostly engaged In active field service and sieges, and few had either leisure or opportunity to devote themselves to improvements in permanent fortification. [335]
Choumara published in 1827. His system contains much originality, and his writings give proof of talent and genius. He has very evidently more originality than judgment, and it is hardly probable that his system will ever be generally adopted in practice.
The Metz system, as arranged by Noizet, as a theoretical study, is undoubtedly the very best that is now known. It, however, requires great modifications to suit it to different localities. For a horizontal site, it is probably the most perfect system ever devised. It is based on the system of Vauban as improved by Cormontaigne, and contains several of the modifications suggested by modern engineers. It is applied in a modified form to the new fortifications of Paris.
Baron Rohault de Fleury has introduced many modifications of the ordinary French system in his new defences of Lyons. We have seen no written account of these works, but from a hasty examination in 1844, they struck us as being too complicated and expensive.
The new fortifications of Western Germany are modifications of Rempler's system, as improved by De la Chiche and Montalembert. It is said that General Aster, the directing engineer, has also introduced some of the leading principles of Chasseloup and Carnot.
The English engineers have satisfied themselves with following in the track of their continental neighbors, and can offer no claims to originality.
Of the system of fortification now followed in our service we must decline expressing any opinion; the time has not yet arrived for subjecting it to a severe and judicious criticism. But of the system pursued previous to 1820, we may say, without much fear of contradiction, that a worse one could scarcely have been devised. Instead of men of talent and attainments in military science, most of our engineers were then either foreigners, or [336] civilians who owed their commissions to mere political influence. The qualifications of the former were probably limited to their recollection of some casual visit to two or three of the old European fortresses; and the latter probably derived all their military science from some old military book, which, having become useless in Europe, had found it way into this county, which they had read without understanding, and probably without even looking at its date. The result was what might have been anticipated — a total waste of the public money. We might illustrate this by numerous examples. A single one, however, must suffice. About the period of the last war, eight new forts were constructed for the defence of New York harbor, at an expense of some two millions of dollars. Six of these were circular, and the other two were star forts--systems which had been discarded in Europe for nearly two thousand years! Three of these works are now entirely abandoned, two others are useless, and large sums of money have recently been expended on the other three in an attempt to remedy their faults, and render them susceptible of a good defence. Moreover a number of the works which were constructed by our engineers before that corps was made to feel the influence of the scientific education introduced through the medium of the Military Academy--we say, a considerable number of our fortifications, constructed by engineers who owed in their plans, but have been made of such wretched materials and workmanship that they are already crumbling into ruins.
A fortification, in its most simple form, consists of a mound of earth, termed the rampart, which encloses the space fortified a parapet, surmounting the rampart and covering the men and guns from the enemy's projectiles; a scarp wall, which sustains the pressure of the earth of [337] the rampart and parapet, and presents an insurmountable obstacle to an assault by storm; a wide and deep ditch, which prevents the enemy from approaching near the body of the place; a counterscarp wall, which sustains the earth on the exterior of the ditch; a covered way, which occupies the space between the counterscarp and a mound of earth called a glacis, thrown up a few yards in front of the ditch for the purpose of covering the scarp of the mainly work.
The work by which the space fortified is immediately enveloped, is called the enceinte, or body of the place. Other works are usually added to the enceinte to strengthen the weak points of the fortification, or to lengthen the siege by forcing the enemy to gain possession of them before he can breach the body of the place: these are termed outworks, when enveloped by the covered way, and advanced works, when placed exterior to the covered way, but in some way connected with the main work; but if entirely beyond the glacis, and not within supporting distance of the fortress, they are called detached works.
In a bastioned front the principal outwork is the demilune, which is placed in front of the curtain; it serves to cover the main entrance to the work, and to place the adjacent bastions in strong re-enterings.
The tenaille is a small low work placed in the ditch, to cover the scarp wall of the curtain and flanks from the fire of the besieger's batteries erected along the crest of the glacis.
The places of arms, are points where troops are assembled in order to act on the exterior of the work. The reentering places of arms, are small redans arranged at the points of junction of the covered ways of the bastion and demi-lune. The salient places of arms are the parts of the covered way in. front of the salients of the bastion and demi-lune.
Small permanent works, termed redoubts, are placed [338] within the demi-lune arid re-entering places of arms for strengthening those works. Works of this character constructed within the bastion are termed interior retrenchments; when sufficiently elevated to command the exterior ground, they are called cavaliers.
Caponniers are works constructed to cover the passage of the ditch from the tenaille to the gorge of the demilune, and also from the demi-lune to the covered way, by which communication may be maintained between the enceinte and outworks.
Posterns are underground communications made through the body of the place or some of the outworks.
Sortie-passages are narrow openings made through the crest of the glacis, which usually rise in the form of a ramp from the covered way, by means of which communication may be kept up with the exterior. These passages are so arranged that they cannot be swept by the fire of the enemy. T(he other communications above ground are called ramps, stairs, &c.
Traverses are small works erected on the covered way to intercept the fire of the besieger's batteries.
Scarp and counterscarp galleries are sometimes constructed for the defence of the ditch. They are arranged with loop-holes, through which the troops of the garrison fire on the besiegers when they have entered the ditch, without being themselves exposed to the batteries of the enemy.
In sea-coast defences, and sometimes in a land front for the defence of the ditch, embrasures are made in the scarp wall for the fire of artillery; the whole being protected from shells by a bomb-proof covering over head: this arrangement is termed a casemate.
Sometimes double ramparts and parapets are formed, so that the interior one shall fire over the more advanced; the latter in this case is called a faussebraie. [339]
If the inner work be separated from the other it is called a retrenchment,1 and if in addition it has a commanding fire, it is termed, as was just remarked, a cavalier.
The capital of a bastion is a line bisecting its salient angle. All the works comprehended between the capitals of two adjacent bastions is termed a front: it is taken as the unit in permanent fortification.
Fig. 39 represents the ground plan of a modern bastioned front, of a regular and simple form, on a horizontal site.
A, A, A--Is the enceinte, or body of the place.
B--The bastions.
C--The main ditch.
D--The covered ways.
E--The re-entering places of arms.
F--The salient places of arms.
G--The demi-lune.
H--The demi-lune ditch.
J--The demi-lune redoubt.
L--The ditch of the demi-lune redoubt,
M--The redoubt of the reentering places of arms.
N--The ditches of the redoubts.
O--The tenaille.
P--The double caponnier.
a--The traverses.
b--The sortie-passages.
c--Stairs.
d--Cut in the demi-lune to flank the redoubt of the re-entering place of arms.
Fig. 40 represents a section through the line mn‘ of the preceding figure.
A--Is the rampart.
B--The parapet.
C--The ditch.
D--The scarp wall.
E--The counterscarp wall.
F--The glacis.
G--The covered way.
H--The terre-plein.
J--The parade.
Sometimes half embrasures are cut in the earthen parapet of a fort, so as to sink the gun below the crest, and thus more effectually cover the men from the enemy's fire. [340] But guns in embrasure have a far less extended field of fire than when mounted in barbette; moreover, the embrasures present openings through which an enemy may penetrate in an assault. Owing to these objections, they are employed only for the protection of particular points; that is, where it is important to cover the artillerists from the enemy's fire, or where the guns are to be used merely to protect a ditch, or to enfilade a road, &c. The bottom of the embrasure is called the sole, the sides are called cheeks, and the mass of earth between two embrasures, the merlon. Embrasures may be made either direct or oblique, according as the fire is required to be perpendicular or oblique to the parapet.
A coverport is a small outwork of any convenient form, erected immediately in front of a gateway, to screen it from the enemy's fire.
A counterguard is a more extensive work, constructed in front of a part of the fortress itself, or of some other outwork of greater importance, which it is intended to cover. These are sometimes called coverfaces, from their situation and object; but the former term is most commonly used.
Sometimes outworks, called tenaillons, consisting of one long and one short face, are placed on each side of the demi-lune of a front of fortification, for the purpose of prolonging the siege. (Fig. 41.)
Small, or demi-tenaillons, are frequently so arranged as to cover only one-half of the demi-lune, and then a bonnet constructed in front of the salient of the demi-lune. (Fig. 42.) In this case the bonnet is flanked by the short faces of the demi-tenaillons ; these short faces are themselves flanked by the demi-lune, while the bastions flank the long faces.
A hornwork consists of a front of fortification, and two wings resting on the faces of bastions of a front of the [341] fortress. It sometimes has also a demi-lune or bonnet, as in the case of demi-tenaillons. (Fig. 43.)
A crownwork consists of two fronts of fortification, and two wings. (Fig. 44.) It is sometimes made double, and even triple.
These works are also employed as advanced works and placed entirely in front of the glacis. They have generally been added to a fortress for the purpose of occupylng some important piece of ground not included within the limits of the main work. They may be constructed with covered ways, and sometimes it may be found advantageous to secure them by retrenchments.
A detached work may be made in any form deemed best suited to the site. Being but remotely connected with the fortress, the latter will exercise but slight influence on the character of its plan or construction. They are usually of limited extent and slight relief, partaking much of the nature of field-works.2
