Fortification (1859)

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After Engels had written his articles beginning with C, his work for The New American Cyclopaedia was interrupted. But on March 15, 1859, Charles Dana asked Marx to write articles “Fortification” and “Infantry”. They were in fact written by Engels.

On June 10, 1859 Marx acknowledged receipt of Engels’ “Fortification”, which he described as “splendid”. He wrote: “I must say I feel some twinges of conscience about having made such demands on the little spare time you have.” Dana acknowledged receipt of the article in a letter to Marx of July 30. Engels’ excerpts from the article “Fortification” in the Encyclopaedia Britannica (Vol. IX, Edinburgh, 1855) survive. This was however far from Engels’ only source for his article (some of them are mentioned in the text). “Fortification” was published in 1859 in Vol. VII of the Cyclopaedia. The editors added, with an explanatory note, a table of US fortifications, p. 317

This subject is sometimes divided into defensive fortification, which provides the means of rendering a given locality, permanently or for a short time only, capable of defence; and offensive fortification, which contains the rules for conducting a siege. We shall, however, treat of it here under the three heads of permanent fortification, or the mode of putting a locality, in time of peace, in such a state of defence as to compel the enemy to attack it by a regular siege; the art of sieges; and field fortification, or the construction of temporary works to strengthen a given point in consequence of the momentary importance which it may acquire under the peculiar circumstances of a campaign.

I. Permanent Fortification

The oldest form of fortification appears to be the stockade, which up to the end of the 18th century was still the national system with the Turks (palanka), and is even now in full use in the Indo-Chinese peninsula among the Burmese. It consists of a double or triple row of stout trees, planted upright and near each other in the ground, forming a wall all around the town or camp to be defended. Darius in his expedition among the Scythians, Cortes at Tabasco in Mexico, and Capt. Cook in New Zealand, all came in contact with such stockades. Sometimes the space between the rows of trees was filled up wiThearth; in other instances the trees were connected and held together by wicker work.

The next step was the erection of masonry walls instead of stockades. This plan secured greater durability, at the same time that it rendered the assault far more difficult; and from the days of Nineveh and Babylon down to the close of the middle ages, masonry walls formed the exclusive means of fortification among all the more civilized nations. The walls were made so high that escalade was rendered difficult; they were made thick enough to offer a lengthened resistance to the battering ram, and to allow the defenders to move about freely on the top, sheltered by a thinner masonry parapet with battlements, through the embrasures of which arrows and other missiles might be shot or thrown against the assailants. To increase the defence, the parapet was soon built overhanging, with holes between the projecting stones on which it rested, so as to allow the besieged to see the foot of the wall and reach an enemy who might have got so far by direct missiles from above. The ditch, no doubt, was also introduced at an early period, surrounding the whole wall, and serving as the chief obstacle against access to it.

Finally, the defensive capabilities of masonry walls were developed to the highest point by adding at intervals towers which projected from the wall, thus giving it a flanking defence by missiles thrown from them at such troops as assailed the space between two towers. Being in most cases higher than the wall, and separated from its top by cross parapets, they commanded it and formed each a small fortress, which had to be taken singly after the defenders had been driven from the main wall itself. If we add to this, that in some cities, especially in Greece, there was a kind of citadel, on some commanding height inside the walls (acropolis), forming a réduit and second line of defence, we shall have indicated the most essential points of the fortification of the masonry epoch.

But from the 14th to the end of the 16th century the introduction of artillery fundamentally changed the modes of attacking fortified places. From this period dates that immense literature on fortification which has produced systems and methods innumerable, part of which have found a more or less extensive practical application, while others, and not always the least ingenious, have been passed over as merely theoretical curiosities, until at later periods the fruitful ideas contained in them have been again drawn into daylight by more fortunate successors. This has been the fate, as we shall see, of the very author who forms, if we may say so, the bridge between the old masonry system and the new system of earthworks merely revetted with masonry in those places which the enemy cannot see from a distance.

The first effect of the introduction of artillery was an a increase in the thickness of the walls and in the diameter of the towers at the expense of their height. These towers were now called roundels (rondelli), and were made large enough to hold several pieces of cannon. To enable the besieged to work cannon on the wall too, a rampart of earth was thrown up behind it so as to give it the necessary width. We shall soon see how this earthwork gradually encroached on the wall, so as in some cases to supersede it altogether. Albert Dürer, the celebrated German painter, developed this system of roundels to its highest perfection. He made them perfectly independent forts, intersecting the continuity of the wall at certain intervals, and with casemated batteries enfilading the ditch; of his masonry parapets, not more than 3 feet high is uncovered (visible to the besieger and subject to his direct fire); and in order to complete the defence of the ditch, he proposed caponnières, casemated works on the sole of the ditch, hidden from the eyes of the besiegers, wiThembrasures on either side so as to enfilade the ditch as far as the next angle of the polygon. Almost all these proposals were new inventions; and if none except the casemates found favor with his age, we shall see that in the latest and most important systems of fortification they have all been adopted and developed according to the altered circumstances of modern times.

About the same time, a change was adopted in the shape of the enlarged towers from which modern systems of fortification may be considered to date. The round shape had the disadvantage that neither the curtain (the piece of wall between two towers) nor the next adjoining towers could reach with their fire every point in front of an intermediate tower; there were small angles close to the wall, where the enemy, if he once reached them, could not be touched by the fire of the fortress. To avoid this, the tower was changed into an irregular pentagon, with one side turned toward the interior of the fortress, and 4 toward the open country. This pentagon was called a bastion. To prevent repetitions and obscurity, we shall now at once proceed to give the description and nomenclature of bastionary defence, based on one of those systems which show all its essential particulars.

Fig. 1 (see next page) represents 3 fronts of a hexagon fortified according to Vauban’s first system. The left side represents the mere outline as used in the geometrical delineation of the work; the right gives the ramparts, glacis, &c, in detail. The entire side of the polygon /’/ “ is not formed by a continuous rampart; at each end, the portions d’ f and e” f” are left open and the space thus arising is closed by the projecting pentagonal bastion d’ b’ a’ c’ e’. The lines a’ b’ and a’ c’ form the faces, the lines b’ d’ and c’ e’ the flanks of the bastion. The points where faces and flanks meet are called the shoulder points. The line a’ /’ which goes from the centre of the circle to the point of the bastion, is called the capital. The line e” d’, forming part of the original circumference of the hexagon, is the curtain. Thus every polygon will have as many bastions as sides. The bastion may be either full, if the whole pentagon is filled up wiThearth as high as the terreplein of the rampart (the place where the guns stand), or hollow (empty) if the rampart slopes down, immediately behind the guns, into the interior. In fig. 1, d b a c e is a full bastion; next one to the right, of which one half only is seen, is a hollow one. Bastions and curtains together constitute the enceinte, or body of the place.

In them we notice, on the terreplein, first the parapet, constructed in front so as to shelter the defenders, and then the ramps, on the interior slope (5 5), by which the communications with the interior are kept up. The rampart is high enough to cover the houses of the town from direct fire, and the parapet thick enough to offer lengthened resistance to heavy artillery. All round the rampart is the ditch t t t t, and in it are several classes of outworks. First, the ravelin or demilune k I m, in front of the curtain, a triangular work with two faces, k I and / m, each with a rampart and parapet to receive artillery. The open rear of any work is called the gorge; thus in the ravelin, k m, in the bastion d e, is the gorge. The parapet of the ravelin is about 3 or 4 feet lower than the parapet of the body of the place, so that it is commanded by it, and the guns of the latter may in case of need Fortification 321 fire away over it. Between the curtain and ravelin there is a long and narrow detached work in the ditch, the tenaille, g h i, destined principally to cover the curtains from breaching fire; it is low and too narrow for artillery, and its parapet merely serves for infantry to flank the ditch fire into the lunette in case of a successful assault. Beyond the ditch is the covered way, nop, bounded on the inner side by the ditch and on the outer side by the interior slope of the glacis, r r r, which from its highest inner boundary line or crest (crête) slopes very gradually down into the field. The crest of the glacis is again 3 feet or more lower than the ravelin, so as to allow all the guns of the fortress to fire over it. Of the slopes in these earthworks the exterior one of the body of the place and of the outworks in the ditch (scarp), and the exterior one of the ditch (from the covered way downward) or counterscarp, are generally revetted with masonry. The salient and reentering angles of the covered way form large, roomy, sheltered spots, called places of arms; they are called either salient (o) or reentering (n p), according to the angles at which they are situated. To prevent the covered way from being enfiladed, traverses or cross parapets are constructed across it at intervals, leaving only small passages at the end nearest the glacis. Sometimes there is a small work constructed to cover the communication across the ditch from the tenaille to the ravelin; it is called a caponniere, and consists of a narrow pathway covered on either side by a parapet, the exterior surfaces of which slope down gradually like a glacis. There is such a caponniere between the tenaille g h i and the ravelin k I m, fig.1.

The section given in fig. 2 will assist in rendering this description clearer. A is the terreplein of the body of the place, B is the parapet, C the masonry revetment of the scarp, D the ditch, E the cunette a smaller and deeper ditch drawn across the middle of the larger one, F the masonry revetment of the counterscarp, G the covered way, H the glacis. The steps shown behind the parapet and glacis are called banquettes, and serve as stands for infantry to step on and fire over the protecting parapet. It will be readily observed from the diagram that the guns placed on the flanks of the bastions sweep the whole ditch in front of the adjoining bastions. Thus the face a’ b’ is covered by the fire of the flank c” e”, and the face a’ c’ by the flank b d. On the other hand, the inner faces of two adjoining bastions cover the faces of the ravelin between them, by keeping the ditch in front of the ravelin under their fire. Thus there is no portion of the ditch unprotected by a flanking fire; in this consists the original and great step in advance by which the bastionary system inaugurates a new epoch in the history of fortification.

The inventor of bastions is not known, nor is the precise date at which they were introduced; the only thing certain is that they were invented in Italy, and that San Michèle in 1527 constructed two bastions in the rampart of Verona. All statements respecting earlier bastions are doubtful. The systems of bastionary fortification are classed under several national schools; the first to be mentioned is of course that which invented bastions, the Italian. The first Italian bastions bore the stamp of their origin; they were nothing but polygonal towers or roundels; they scarcely altered the former character of the fortification, except as regarded the flanking fire.

The enceinte remained a masonry wall, exposed to the direct fire of the enemy; the rampart of earth thrown up behind served chiefly to give room to place and handle artillery, and its inner slope was also revetted with masonry, as in the old town walls. It was not till a later day that the parapet was constructed of earthworks, but even then the whole of its outer slope up to the top was revetted with masonry exposed to the direct fire of the enemy. The curtains were very long, from 300 to 550 yards. The bastions were very small, the size of large roundels, the flanks always perpendicular to the curtains. Now as it is a rule in fortification that the best flanking fire always comes from a line perpendicular to the line to be flanked, it is evident that the chief object of the old Italian flank was to cover, not the short and distant face of the adjoining bastion, but the long straight line of the curtain. Where the curtain became too long, a flat, obtuse-angled bastion was constructed on the middle of it, and called a platform (piatta forma).

The flanks were not constructed on the shoulder point, but a little retired behind the rampart of the faces, so that the shoulder points projected and were supposed to shelter them; and each flank had two batteries, a lower one, and a higher one a little to the rear; sometimes even a casemate in the scarp wall of the flank on the bottom of the ditch. Add to this a ditch, and you have the whole of the original Italian system; there were no ravelins, no tenailles, no covered way, no glacis. But this system was soon improved. The curtains were shortened, the bastions were enlarged. The length of the inner side of the polygon (/’ /’ , fig. 1) was fixed at from 250 to 300 yards. The flanks were made longer, l

/G of the side of the polygon,

XU of the length of the curtain. Thus, though they remained perpendicular to the curtain and had other defects, as we shall see, they now began to give more protection to the face of the next bastion. The bastions were made full, and in their centre a cavalier was often erected, that is, a work with faces and flanks parallel to those of the bastion, but with a rampart and parapet so much higher as to admit of its firing over the parapet of the bastion. The ditch was very wide and deep, the counterscarp running generally parallel to the face of the bastion; but as this direction of the counterscarp prevented the part of the flank nearest the shoulder from seeing and flanking the whole of the ditch, it was subsequently done away with, and the counterscarp was traced so that its prolongation passed through the shoulder point of the next bastion. The covered way was then introduced (first in the citadel of Milan, in the 2d quarter of the 16th century, first described by Tartaglia in 1554).

It served as a place of concentration as well as of retreat for sallying parties, and from its introduction the scientific and energetic use of offensive movements in the defence of fortresses may be said to date; to increase its utility the places of arms were introduced, which give more room, and of which the reentering angles also give a capital flanking fire to the covered way. To render the access to the covered way still more difficult, rows of palisades were erected on the glacis, one or two yards from its crest, but in this position they were soon destroyed by the enemy’s fire; after the middle of the 17th century, therefore, they were placed, at the suggestion of the Frenchman Maudin, on the covered way, covered by the glacis.

The gates were in the middle of the curtain; to cover them, a crescent-shaped work was placed in the middle of the ditch in front of them; but for the same reason that the towers were transformed into bastions, the half-moon (demi-lune) was soon changed into a triangular work—the present ravelin. This was still very small, but became larger when it was found that not only did it serve as a bridge-head across the ditch, but also covered flanks and curtains against the enemy’s fire, gave a cross fire in front of the capitals of the bastions, and effectually flanked the covered way. Still they were made very small, so that the prolongation of their faces reached the body of the place in the curtain point (the extremity of the curtain). The principal faults of the Italian mode of fortification were the following: 1. The bad direction of the flank. After the introduction of ravelins and covered ways, the curtain became less and less the point of attack; the faces of the bastions now were chiefly assailed. To cover these well, the prolongation of the faces should have met the curtain at the very point where the flank of the next bastion was erected, and this flank should have been perpendicular or nearly so to this prolonged line (called the line of defence). In that case there would have been an effective flanking fire all along the ditch and front of the bastion. As it was, the line of defence was neither perpendicular to the flanks nor did it join the curtain at the curtain point; it intersected the curtain at 1/4, 1/3, or 1/2 of its length.

Thus, the direct fire of the flank was more likely to injure the garrison of the opposite flank than the assailants of the next bastion. 2. There was an evident want of provision for a prolonged defence after the enceinte had been breached and successfully assaulted at one single point. 3. The small ravelins but imperfectly covered the curtains and flanks, and received but a poor flanking fire from them. 4. The great elevation of the rampart, which was all faced or revetted with masonry, exposed, in most cases, a height of 15 to 20 feet of masonry to the direct fire of the enemy, and of course this masonry was soon destroyed. We shall find that it took almost two centuries to eradicate this prejudice in favor of uncovered masonry, even after the Netherlands had proved its uselessness. The best engineers and authors belonging to the Italian school were: San Michèle (died 1559), fortified Napoli di Romania in Greece, and Candia, and built Fort Lido near Venice; Tartaglia (about 1550); Alghisi da Carpi, Girolamo Maggi, and Giacomo Castriotto, who about the end of the 16th century all wrote on fortification. Paciotto of Urbino built the citadels of Turin and Antwerp (1560-’70). The later Italian authors on fortification, Marchi, Busca, Floriani, Rossetti, introduced many improvements, but none of these were original. They were mere plagiarists of more or less skill; they copied most of their devices from the Germandaniel Speckle, and the remainder from the Netherlanders. They all belong to the 17th century, and were completely eclipsed by the rapid development of fortificatory science which at that time took place in Germany, the Netherlands, and France.

The defects of the Italian system of fortification were soon discovered in Germany. The first man to point out the chief defect of the elder Italian school, the small bastions and long curtains, was a German engineer, Franz, who fortified for Charles V the town of Antwerp. In the council held to try the plan, he insisted upon larger bastions and shorter curtains, but was outvoted by the duke of Alva and the other Spanish generals, who believed in nothing but the routine of the old Italian system. Other German fortresses were distinguished by the adoption of casemated galleries upon the principle of Dürer, as Küstrin, fortified in 1537-’58, and Jülich, fortified a few years later by an engineer known under the name of Master John (Meister Johann).

But the man who first broke completely through the fetters of the Italian school and laid down the principles on which the whole of the subsequent systems of bastionary fortification are founded, was Daniel Speckle, engineer to the town of Strasbourg (died 1589). His chief principles were: 1. That a fortress becomes stronger the more sides there are to the polygon which forms the enceinte, the different fronts being thereby enabled to give a better support to each other; consequently, the nearer the outline to be defended comes to a straight line, the better. This principle, demonstrated as an original discovery with a great show of mathematical learning by Cormontaigne, was thus very well known to Speckle 150 years earlier. 2. Acute-angled bastions are bad; so are obtuse-angled; the salient angle should be a right one. Though correct in his opposition to acute salients (the smallest admissible salient angle is now generally fixed at 60°), the partiality of his time for right-angled salients made him hostile to the obtuse salient, which is indeed very advantageous and unavoidable in polygons with many sides. In fact, this appears to have been merely a concession to the prejudices of his time, for the diagrams of what he considers his strongest method of fortification all have obtuse-angled bastions. 3. The Italian bastions are far too small; a bastion must be large. Consequently, Speckle’s bastions are larger than those of Cormontaigne. 4. Cavaliers are necessary in every bastion and on every curtain. This was a consequence of the system of siege of his time, in which high cavaliers in the trenches played a great part. But in Speckle’s intention, the cavaliers were to do more than resist these; they are real coupures provided beforehand in the bastion, forming a second line of defence after the enceinte has been breached and stormed.

The whole of the credit generally given to Vauban and Cormontaigne for cavaliers forming permanent coupures, is therefore in reality due to Speckle. 5. A portion, at least, of the flank, and better still the whole of the flank of a bastion, must be perpendicular to the line of defence, and the flank be erected in the point where the line of defence crosses the curtain. This important principle, the alleged discovery of which forms the greater part of the glory of the French engineer Pagan, was thus publicly proclaimed 70 years before Pagan. 6. Casemated galleries are necessary for the defence of the ditch; consequently Speckle has them both on the faces and flanks of the bastion, but only for infantry; if he had made them large enough for artillery, he would in this respect have been fully up to the latest improvements. 7.

To be useful, the ravelin must be as large as possible; accordingly, Speckle’s ravelin is the largest ever proposed. Now, Vauban’s improvements upon Pagan consist partly, and Cormontaigne’s improvements upon Vauban consist almost entirely, in the successive enlargement of the ravelin; but Speckle’s ravelin is a good deal larger than even Cormontaigne’s. 8. The covered way is to be strengthened as much as possible. Speckle was the first to see the immense importance of the covered way, and he strengthened it accordingly.

The crests of the glacis and of the counterscarp were formed en crémaillère (like the edge of a saw), so as to render enfilading fire ineffective. Cormontaigne, again, took up this idea of Speckle’s; but he retained the traverses (short ramparts across the covered way against enfilading fire), which Speckle rejected. Modern engineers have generally come to the conclusion that Speckle’s plan is better than Cormontaigne’s. Speckle, beside, was the first to place artillery on the places of arms of the covered way. 9. No piece of masonry is to be exposed to the eye and direct fire of the enemy, so that his breaching batteries cannot be established before he has arrived on the crest of the glacis.

This most important principle, though established by Speckle in the 16th century, was not generally adopted until Cormontaigne; even Vauban exposes a good deal of his masonry. (See C, fig. 2.) In this short abstract of Speckle’s ideas the fundamental principles of all modern bastionary fortification are not only contained but plainly stated, and his system, which even now would afford very good defensive works, is truly wonderful considering the time in which he lived. There is not a celebrated engineer in the whole history of modern fortification who cannot be proved to have copied some of his best ideas from this great original source of bastionary defence. Speckle’s practical engineering skill was shown in the construction of the fortresses of Ingolstadt, Schlettstadt, Hagenau, Ulm, Colmar, Basel, and Strasbourg, all of which were fortified under his direction.

About the same epoch, the struggle for the independence of the Netherlands gave rise to another school of fortification. The Dutch towns, whose old masonry walls could not be expected to resist a regular attack, had to be fortified against the Spaniards; there was, however, neither time nor money for the erection of the high masonry bastions and cavaliers of the Italian system. But the nature of the ground offered other resources in its low elevation above the water horizon, and consequently the Dutch, expert in canal and dike building, trusted to the water for their defence. Their system was the exact counterpart of the Italian: wide and shallow wet ditches, from 14 to 40 yards across; low ramparts without any masonry revetment, but covered by a still lower advanced rampart (fansse-braie) for the stronger defence of the ditch; numerous outworks in the ditch, such as ravelins, half moons (ravelins in front of the salient of the bastion), horn and crown works; and finally, a better use of the accidents of the ground than with the Italians. The first town fortified entirely by earthworks and wet ditches was Breda (1533). Subsequently the Dutch method received several improvements: a narrow zone of the scarp was revetted with masonry, as the wet ditches, when frozen over in winter, were easily passed by the enemy; locks and sluices were constructed in the ditch, so as to let the water in at the moment when the enemy had begun to sap the hitherto dry bottom; and finally, sluices and dikes were constructed for a systematic inundation of the country around the foot of the glacis. The writers on this elder Dutch method of fortification are Marolois (1627), Freitag (1630), Völker (1666), Melder (1670). An application of Speckle’s maxims to the Dutch method was attempted by Scheither, Neubauer, Heidemann, and Heer (all from 1670 to 1690, and all of them Germans).

Of all the different schools of fortification, the French has enjoyed the greatest popularity; its maxims have found practical application in a greater number of still existing fortresses than those of all the other schools put together. Still, there is no school so poor in original ideas. There is neither a new work nor a new principle in the whole of the French school which is not borrowed from the Italians, the Dutch, or the Germans. But the great merit of the French is the reduction of the art to precise mathematical rules, the symmetrical arrangement of the proportions of the different lines, and the adaptation of the scientific theory to the varied conditions given by the locality to be fortified. Errard of Bar-le-Duc (1594), commonly called the father of French fortification, has no claim to the appellation; his flanks form an acute angle with the curtain, so as to be still more ineffective than those of the Italians. A more important name is Pagan (1645).

He was the first to introduce in France, and to popularize, Speckle’s principle that the flanks should be perpendicular to the lines of defence. His bastions are roomy; the proportions between the lengths of faces, flanks, and curtains are very good; the lines of defence are never longer than 240 yards, so that the whole of the ditch, but not the covered way, is within musket range from the flanks. His ravelin is larger than that of the Italians, and has a réduit or keep in its gorge, so as to admit of resistance when its rampart has already been taken. He covers the faces of the bastions with a narrow detached work in the ditch, called a counter-guard, a work which had already been used by the Dutch (the Germandilich appears to have first introduced it). His bastions have a double rampart on the faces, the second to serve as a coupure; but the ditch between the two ramparts is entirely without flanking fire. The man who made the French school the first in Europe was Vauban (1633-1707), marshal of France. Although his real military glory rests upon his two great inventions in the attack of fortresses (ricochet fire and parallels), still he is popularly better known as a constructor of them.

What we have said of the French school is true of Vauban’s method in the highest degree. We see in his constructions as great a variety of forms as is compatible with the bastionary system; but there is nothing original among them, much less any attempt to adopt other forms than the bastionary. But the arrangement of the details, the proportions of the lines, the profiles, and the adaptation of the theory to the ever-varying requirements of the locality, are so ingenious, that they appear perfection in comparison to the works of his predecessors, so that scientific and systematic fortification may be said to date from him. Vauban, however, did not write a line on his method of fortification, but from the great number of fortresses constructed by him the French engineers have tried to deduce the theoretical rules he followed, and thus have been established 3 methods, called Vauban’s first, second, and third system.

Fig. 1 gives the first system in its greatest simplicity. The chief dimensions were: the outer side of the polygon, from the point of one bastion to that of the next, 300 yards (on an average); on the middle of this line, a perpendicular o> ß, 1/6 of the first; through ß, the lines of defence from a” and a’, a” d’ and a’ e”. From the points a” and a’, 2/7 of a” a’ measured on the lines of defence gives the faces a” c” and a’ b’. From the shoulder points c” and b’ arcs with the radius c” d’ or b’ e” were drawn between the lines of defence, giving the flanks b’ d’ and c” e”. Draw e” d’, the curtain. The ditch: with radius 30 yards, an arc in front of the point of the bastion, prolonged by tangents drawn to this arc from the shoulder points of the adjoining bastions, gives the counterscarp. The ravelin: from the curtain point e”, with radius e” y (7, a point on the opposite face 11 yards beyond the shoulder-point), draw the arc 7 8, until it crosses the prolongation of the perpendicular ex ß; this gives the point of the ravelin; the chord to the arc just described gives the face, which is continued from the point until it reaches the prolongation of the tangent forming the counterscarp of the main ditch; the gorge of the ravelin is fixed by this line equally, so that the whole of the ditch remains free for the fire of the flanks.

In front of the curtain, and there alone, Vauban retained the Dutch fausse-braie; this had already been done by the Italian Floriani before him, and the new work had been called tenaille (tenaglia). Its faces were in the direction of the lines of defence. The ditch in front of the ravelin was 24 yards wide, the counterscarp parallel to the faces of the ravelin, and the point rounded off. In this manner Vauban obtained roomy bastions, and kept his flanked salient angles well within musket range; but the simplicity of these bastions renders the defence of the place impossible as soon as the face of one bastion is breached. His flanks are not so good as Speckle’s or Pagan’s, forming an acute angle with the lines of defence; but he does away with the 2 and 3 tiers of uncovered guns which figure in most of the Italian and early French flanks, and which were never very useful. The tenaille is intended to strengthen the defence of the ditch by infantry fire, and to cover the curtain from direct breaching fire from the crest of the glacis; but this is very imperfectly done, as the breaching batteries in the reentering place of arms (n, fig. 1) have a full view of the piece of the curtain next to the flank at e. This is a great weakness, as a breach there would turn all the coupures prepared in the bastion as a second line of defence. It arises from the ravelin being still too small. The covered way, constructed without crémaillères, but with traverses, is much inferior to Speckle’s; the traverses prevent not only the enemy, but also the defence, from enfilading the covered way.

The communications between the different works are on the whole good, but still not sufficient for energetic sallies. The profiles are of a degree of strength which is still generally adopted. But Vauban still clung to the system of revetting the whole of the outside of the rampart with masonry, so that at least 15 feet high of masonry was uncovered. This mistake is made in many of Vauban’s fortresses, and once made can only be remedied at an enormous expense by widening the ditch in front of the faces of the bastions, and constructing earthwork counterguards to cover the masonry. During the greater part of his life Vauban followed his first method; but after 1680 he introduced two other methods, having for their object to admit of a prolonged defence after the bastion was breached. For this purpose he took up an idea of Castriotto’s, who had proposed to modernize the old tower and wall fortification by placing detached bastions, isolated, in the ditch, in front of the towers. Both Vauban’s second and third methods agree in this. The ravelin is also made larger, the masonry is a little better covered; the towers are casemated, but badly; the fault that the curtain may be breached between bastion and tenaille is maintained, and renders the detached bastion partly illusory. Still, Vauban considered his second and third methods as very strong. When he handed over to Louis XIV the plan for the fortification of Landau (second system), he said:

“Sire, here is a place that all my art would not suffice to take.”

This did not prevent Landau from being taken 3 times during Vauban’s life (1702, 1703, 1704), and again shortly after his death (1713).

The errors of Vauban were rectified by Cormontaigne, whose method may be considered as the perfection of the bastionary system. Cormontaigne (1696-1752) was a general of engineers. His larger bastions permit the construction of permanent coupures and second lines of defence; his ravelins were nearly as large as those of Speckle, and fully covered that portion of the curtain which Vauban had left exposed. In polygons of .8 and more sides his ravelins were so far advanced that their fire took in the rear the besiegers’ works against the next bastion as soon as he reached the crest of the glacis. In order to avoid this, two ravelins have to be conquered before one bastion can be breached. This mutual support of the large ravelins becomes more and more effective the more the line to be defended approaches a straight one.

The reentering place of arms was strengthened by a réduit. The crest of the glacis is drawn en crémaillère, as with Speckle, but traverses are maintained. The profiles are very good, and the masonry is always covered by the earthworks in front. With Cormontaigne the French school closes, as far as the construction of bastionary defences, with outworks within the ditch, is concerned. A comparison of the gradual development of bastionary fortification from 1600 to 1750, and of its final results as laid down by Cormontaigne, with the principles of Speckle, as stated above, will tend to elucidate the wonderful genius of the German engineer; for although outworks in the ditch have been multiplied to an enormous degree, yet not a single important principle has been discovered during all these 150 years which had not been already clearly and distinctly enunciated by Speckle.

After Cormontaigne, the school of engineers of Mézières (about 1760) made some slight alterations in his system, the principal of which is the return to Speckle’s old rule that the flanks must be perpendicular to the lines of defence. But the principal point for which the school of Mézières is remarkable is that they for the first time construct outworks beyond the covered way. On fronts particularly open to attack they place at the foot of the glacis, on the capital of the bastion, a detached ravelin called a lunette, and thereby approach for the first time to the modern system of permanent intrenched camps. In the beginning of the 19th century Bousmard, a French emigrant who served in Prussia and was killed at Dantzic in 1807, tried still to improve upon Cormontaigne; his ideas are rather complicated, and the most remarkable is that his ravelin, which is very large, is advanced to the foot of the glacis almost so as to take the place and functions, to a certain degree, of the lunette just described.

A Dutch engineer of Vauban’s time, who more than once opposed him in siege warfare wiThequal honor, Baron Coehorn, gave a further development to the old Dutch method of fortification. His system gives a stronger defence even than Cormontaigne’s, by the clever combination of wet and dry ditches, the great facilities offered to sorties, the excellent communications between the works, and the ingenious réduits and coupures in his ravelins and bastions. Coehorn, a great admirer of Speckle, is the only engineer of note who was honest enough to acknowledge how much he owed to him.

We have seen that even before the introduction of bastions, Albert Dürer used caponnières to afford a stronger flanking fire. In his fortified square he even entirely trusts to these caponnières for the defence of the ditch; there are no towers on the corner of the fort; it is a plain square with none but salient angles. To make the enceinte of a polygon entirely coincident with its outline, so as to have all salient and no reentering angles, and to flank the ditch by caponnières, constitutes what is called polygonal fortification, and Dürer must be considered as its father. On the other hand, a star-shaped enceinte, in which salient and reentering angles follow upon each other regularly, and in which each line is both flank and face at once, flanking the ditch of the next line with the portion next to the reentering angle, and commanding the field with the portion next the salient—such an outline constitutes tenaille fortification. The older Italians and several of the older Germans had proposed this form, but it was not developed till afterward.

The system of George Rimpler (engineer to the emperor of Germany, killed in defending Vienna against the Turks in 1683 ) forms a kind of intermediate stage between the bastionary and tenaille system. What he calls intermediate bastions constitute in reality a perfect line of tenailles. He declared himself energetically against open batteries with a mere earth parapet in front, and insisted on casemated batteries wherever they could be erected; especially on the flanks, where 2 or 3 tiers of well covered guns would thus have a far greater effect than the 2 or 3 tiers of guns in open flank batteries, which could never act together. He also insisted on batteries, that is, réduits, in the places of arms of the covered way, which Coehorn and Cormontaigne adopted, and especially a double and triple line of defence behind the salient angles of the enceinte. In this manner his system is remarkably in advance of his time; the whole of his enceinte consists of independent forts, each of which has to be taken separately, and large defensive casemates are used in a manner which reminds us, almost in the details even of their application, of the more recent constructions in Germany.

There is no doubt that Montalembert owed as much to Rimpler as the bastionary system of the 17th and 18th century to Speckle. The author who first fully developed the advantages of the tenaille over the bastionary system was Landsberg (1712); but it would lead us too far if we were to enter into his arguments or describe his fortificatory outline. Of the long series of skilful German engineers who followed Rimpler and Landsberg, we may name the Mecklenburg colonel Buggenhagen (1720), the inventor of blockhouse traverses, or traverses hollowed out and adapted for casemated musketry fire; and the Württemberg major Herbort (1734), inventor of defensive barracks, large barracks in the gorge of salient works, proof against vertical fire, wiThembrasured casemates on the side facing the enceinte, and barracks and store rooms on the side facing the town. Both these constructions are now very largely used.

Thus we see that the German school, with almost the only exception of Speckle, was from its origin adverse to bastions, which it sought to replace chiefly by tenailles, and that it attempted at the same time to introduce a better system of inner defence, chiefly by the use of casemated galleries, which again were considered as the height of absurdity by French engineering authorities. One of the greatest engineers, however, that France ever produced, the marquis de Montalembert (l7l3-’99), majorgeneral of cavalry, passed over with drums beating and colors flying into the camp of the German school, to the great horror of the whole French engineering corps, who, up to the present date, decry every word he has written. Montalembert severely criticized the defects of the bastionary system ; the ineffectuality of its flanking fire; the almost certainty it offered to the enemy that his shots if they missed one line must do harm in another; the want of protection against vertical fire; the perfect uselessness of the curtain as to fire; the impossibility of having good and large coupures in the gorges of the bastions, proved by the fact that no fortress of his time had any of the multifarious permanent coupures proposed by the theorists of the school; and the weakness, bad connection, and want of mutual support of the outworks.

Montalembert therefore preferred either the tenaille or the polygonal system. In either case the body of the place consisted of a row of casemates, with one or two tiers of guns, the masonry of which was covered from direct fire by a counterguard of couvre-face of earthwork extending all around and having a second ditch in its front; this ditch was flanked by casemates in the reentering angles of the couvre-face covered by the parapet of the réduit or lunette in the reentering place of arms. The whole system was based upon the principle of opposing, by means of casemated guns, such an overwhelming fire to the enemy the moment he reached the crest of the glacis, or of the couvre-face, that he could not possibly succeed in erecting his breaching batteries. That casemates could do this he maintained against the unanimous condemnation of French engineers, and he afterward even compiled systems of circular and tenaille fortifications in which all earthworks were rejected and the whole defence intrusted to high casemated batteries with from 4 to 5 tiers of guns, the masonry of which was to be protected by the fire of its batteries only. Thus, in his circular system, he contrives to concentrate 348 guns on any point 500 yards from the fortress, and expects that such an immense superiority of fire would put the possibility of erecting siege batteries entirely out of the question. In this, however, he has found no adherents, except in the construction of the sea fronts of coast forts; here the impossibility of breaching strong casemated walls by the guns of ships was pretty well demonstrated by the bombardment of Sebastopol. The splendid forts of Sebastopol, Cronstadt, Cherbourg, and the new batteries on the entrance of Portsmouth harbor (England), and almost all modern forts for harbor defence against fleets, are constructed according to Montalembert’s principle. The partly uncovered masonry of the Maximilian towers at Lintz (Austria) and of the réduits of the detached forts of Cologne are imitated from Montalembert’s less happy projects. In the fortification of steep heights (Ehrenbreitstein in Prussia, for instance) the uncovered masonry forts have also been sometimes adopted, but what resistance they will be able to make must be decided by actual experience.

The tenaille system has never, to our knowledge at least, found practical application, but the polygonal system is in great favor in Germany, and has been applied to most modern constructions there; while the French tenaciously cling to Cormontaigne’s bastions. The enceinte, in the polygonal system, is generally a plain earthwork rampart with revetted scarp and counterscarp, with large caponnières in the middle of the fonts, and with large defensive barracks behind the rampart and covered by it to serve as coupures. Similar defensive barracks have also been erected as coupures in many bastionary works, to close the gorges of the bastions; the rampart serving as a counterguard to protect the masonry from distant fire.

Of all Montalembert’s proposals, however, that of detached forts has had the greatest success, and initiated a new era, not only in fortification, but in the attack and defence of fortresses, and even in general strategy. Montalembert proposed to surround large fortresses in important situations by a single or double chain of small forts, on commanding elevations, which, though isolated in appearance, would still support each other by their fire, and, by the facility they gave for large sorties, would render a bombardment of the place impossible, and when required form an intrenched camp for an army. Vauban had already introduced permanent intrenched camps under the guns of fortresses, but their intrenchments consisted of long continuous lines, which, if broken through at one point only, were completely at the mercy of the enemy.

But these intrenched camps of Montalembert’s were capable of a far greater resistance, for each fort had to be taken singly, and before 3 or 4 at least were conquered, no enemy could open his trenches against the place. Moreover, the siege of each of the forts could be interrupted at every moment by the garrison, or rather the army encamping behind the forts, and thus a combination of active campaigning and regular fortress warfare was secured, which must greatly strengthen the defence. When Napoleon led his armies hundreds of miles through the enemy’s country, never heeding the fortresses which had all been constructed according to the old system, and when in return the allies (1814 and 1815) marched straight on toward Paris, leaving almost unnoticed in their rear the triple belt of fortresses with which Vauban had endowed France, it became evident that a system of fortification was antiquated which confined its outworks to the main ditch or at the outside to the foot of the glacis. Such fortresses had lost their power of attraction over the large armies of modern times. Their means of doing harm did not extend beyond the range of their cannon.

It thus became necessary to find some new means to break the impetuous movement of modern invading armies, and Montalembert’s detached forts were applied on a large scale. Cologne, Coblentz, Mentz, Rastadt, Ulm, Königsberg, Posen, Lintz, Peschiera, and Verona were severally transformed into large intrenched camps, capable of holding from 60,000 to 100,000 men, but defensible, in case of need, by far smaller garrisons. At the same time, the tactical advantages of the locality to be fortified were placed in the background by the strategetical considerations which now decided the situation of fortresses.

Such places only were fortified as might directly or indirectly stop the progress of a victorious army, and which, being large towns in themselves, offered great advantages to an army by being the centre of the resources of whole provinces. Situations on large rivers, especially at the points of junction of two considerable rivers, were chosen in preference, as they compelled the attacking army to divide its forces. The enceinte was simplified as much as possible, and outworks in the ditch were almost entirely done away with; it was sufficient to have the enceinte safe against an irregular attack.

The principal battle-field lay aroun d the detached forts, and they were to be defended not so much by the fire from their ramparts, as by the sallies of the garrison of the fortress itself. The largest fortress constructed upo n this plan is Paris; it has a simple bastioned enceinte with bastioned forts, almost all squares; ther e is n o outwork, not even a ravelin, in the whole fortification. No doubt, the defensive strength of France has gained 30 per cent, by this new and immense intrenched camp, large enough to afford a refuge for three beaten armies. The intrinsic value of the different methods of fortification has lost a great deal of its importance by this improvement; the cheapest will now be the best; for the defence is now based, not upon the passive system of awaiting the enemy behind the walls until he opens his trenches, and then cannonading them, but upon the active one of taking the offensive with the concentrated strength of the garrison against the necessarily divided forces of the besieger.

II. Sieges

The art of sieges had been brought to a certain perfection by the Greeks and Romans. They tried to breach the walls of fortresses by the battering ram, and approached them under cover of strongly roofed galleries, or in case of need by a lofty construction which was to command walls and towers by its greater height, and offer a safe approach to the storming columns. The introduction of gunpowder did away with these contrivances; the fortresses having now ramparts of less elevation, but a fire effective at long distances, the approaches were made by trenches, leading in zigzags or curved lines toward the glacis; batteries being erected at various spots so as to silence if possible the fire of the besieged and to batter down his masonry.

Once arrived on the crest of the glacis, a high trench cavalier was erected, with the intention of commanding the bastions and their cavaliers, and then by a crushing fire to complete the breach and prepare for the assault. The curtain was the point generally attacked. There was, however, no system in this mode of attack until Vauban introduced parallels of ricochet firing, and regulated the process of sieges in the manner which is in use even now, and still denominated Vauban’s attack. The besieger, after investing the place with a sufficient force on all sides, and choosing the fronts to be attacked, opens the first parallel during the night (all siege works are chiefly carried on at night) at about 600 yards from the fortress. A trench parallel to the sides of the besieged polygon is drawn around at least 3 of these sides and fronts; the earth, being thrown up on the side toward the enemy and propped upon the sides of the ditch with gabions (willow-work baskets filled wiThearth), forms a kind of parapet against the fire of the fortress. In this first parallel the ricochet batteries for enfilading the long lines of the attacked fronts are constructed.

Taking for the object of the siege a bastioned hexagon, there should be ricochet batteries to enfilade the faces of 2 bastions and 3 ravelins, in all the batteries, one for each face. These batteries throw their shot so as to pass just over the parapet of the works and along the faces in their whole length, taking them in flank and endangering guns and men. Similar batteries are constructed to enfilade the branches of the covered way, and mortars and howitzers are placed in\ battery to throw shells into the interior of the bastions and ravelins. All these batteries are covered by earthwork parapets. At the same time, at two or more places, zigzag trenches are pushed forward toward the place, taking care to avoid all enfilading fire from the town; and so soon as the fire of the place shows signs of slacking, the second parallel, about 350 yards from the works, is opened. In this parallel the dismounting batteries are constructed. They serve to completely destroy the artillery and embrasures on the faces of the fortress; there will be 8 faces to attack (2 bastions and their ravelins, and the inner faces of the adjoining ravelins), for each of which there is a battery, constructed parallel to the attacked faces, and each embrasure exactly opposite to an embrasure of the fortress. From the second parallel fresh zigzags are pushed toward the town; at 200 yards the half parallel is constructed, forming new enlargements of the zigzags armed with mortar batteries; and at last, at the foot of the glacis, the third parallel. This is armed with heavy mortar batteries. By this time the fire of the place will have been nearly silenced, and the approaches, in varied forms of curved or angular lines, to avoid ricochet fire, are carried up to the crest of the glacis, which it reaches opposite the points of the two bastions and of the ravelin.

A lodgment or trench and parapet is then formed in the salient place of arms to enfilade the ditch by infantry fire. If the enemy is active and daring in his sorties, a 4th parallel connecting the salient places of arms across the glacis becomes necessary. Otherwise a sap is pushed from the 3d parallel to the reentering places of arms, and the crowning of the glacis, or the construction of a trench all along the covered way on the crest of the glacis, is completed. Then the counter batteries are constructed in this couronnement in order to silence the fire of the flank, which enfilades the ditch, and after them the breaching batteries against the point and faces of the bastions and ravelin. Opposite the points to be breached, a mining gallery is constructed leading down from the trenches through the glacis and counterscarp into the ditch; the counterscarp is blown in, and a fresh trench constructed across the ditch to the foot of the breach, covered on the side whence the enfilading fire of the flank comes by a parapet. As soon as both breach and passage of the ditch are complete, the assault takes place. This is in the case of a dry ditch; across a wet ditch, a dike has to be constructed with fascines, covered equally by a parapet on the side of the flank of the adjoining bastion. If on taking the bastion it is found that there is a further intrenchment or coupure in the rear, a lodgment has to be effected, fresh batteries to be constructed on the breach, and a fresh breach, descent, and passage of the ditch and assault to be made. The average resistance of a bastioned hexagon of Vauban’s first method against such a siege is calculated to be from 19 to 22 days if there are no coupures, and 27 or 28 days if it is provided with coupures. Cormontaigne’s method is expected to hold out 25 or respectively 35 to 37 days.

III. Field Fortification

The construction of field works is as old as the existence of armies. The ancients were even far more expert in this art than our modern armies; the Roman legions, before an enemy, intrenched their camp every night. During the 17th and 18th centuries we see also a very great use of field works, and in the wars of Frederick the Great pickets on outpost duty generally threw up slightly profiled redans. Yet even then, and it is still more the case now, the construction of field works was confined to the strengthening of a few positions selected beforehand with a view to certain eventualities during a campaign. Thus Frederick the Great’s camp at Bunzelwitz, Wellington’s lines at Torres Vedras, the French lines of Weissenburg, and the Austrian intrenchments in front of Verona in 1848.

Under such circumstances, field works may exercise an important influence upon the issue of a campaign by enabling an inferior army successfully to resist a superior one. Formerly the intrenched lines, as in Vauban’s permanently intrenched camps, were continuous; but from the defect that if pierced and taken at one point the whole line was useless, they are now universally composed of one or more lines of detached redoubts, flanking each other by their fire, and allowing the army to fall upon the enemy through the intervals as soon as the fire of the redoubts has broken the energy of his assault. This is the principal use of field works; but they are also employed singly, as bridge-heads to defend the access to a bridge, or to close an important pass to small parties of the enemy.

Omitting all the more fanciful shapes of works which are now out of date, such fortifications should consist of works either open or closed at the gorge. The former will either be redans (two parapets with a ditch in front forming an angle facing the enemy) or lunettes (redans with short flanks). The latter may be closed at the gorge by palisadings. The principal closed field work now in use is the square redoubt, either as a regular or an irregular quadrangle, closed by a ditch and parapet all round. The parapet is made as high as in permanent fortification (7 to 8 feet), but not so thick, having to resist field artillery only. As none of these works has a flanking fire in itself, they have to be disposed so that they flank each other within musket range. To do this effectually, and strengthen the whole line, the plan now most generally adopted is to form an intrenched camp by a line of square redoubts flanking each other, and also a line of simple redans, situated in front of the intervals of the redoubts. Such a camp was formed in front of Comoro, south of the Danube, in 1849, and w.as defended by the Hungarians for 2 days against a far superior army.