Part 158

I construct the bastions and flanks out of the sides of the counter-guard, which are detached by means of a ditch 4 toises wide. This ditch is covered above by vaults made of brick or timber, and by boards well supported underneath by strong stakes, the whole being strengthened and rendered bomb-proof with earth 3 or 4 feet thick. This earth keeps the upper plan of the bastion compact, and is sufficient to form a parapet to the counter-guard when the bastion is destroyed. If the vaults should be blown up by mines, and the besiegers set fire to the beams that supported them, a fresh work will present itself, together with a ditch which they had not foreseen or expected, and which they must cross before any further impression can be made.

This sort of subterraneous fortification is extremely advantageous, and may be converted to various purposes. It serves for casemates and galleries to the mines, which I would construct along the whole extent of the faces belonging to these bastions; a communication with them is kept up by means of the galleries attached to the counter-guard. These galleries must be blocked up the instant the bastion is demolished. The flanks of the side will be built after the same method, with a ditch as wide as the one dug in front of the bastion, and which, according to circumstances, may be uncovered, like that already described. The flanks will be of a round figure, in order to avoid the projection of any angles towards the body of the place, which would be the case, should the work be carried; for the enemy availing himself of the earth in front of the walls, and throwing it up, would derive considerable advantage from these angles.

The principal advantage to be obtained from my system arises out of the double defence which it affords to the saliant angles of the bastions, by covering a part of the demi-lunes mitrées, or mitred half-moons (which are their chief protection,) and by these means concealing the body of the place from any outward command, or eminence. This cover or defence cannot, in fact, be taken, before the enemy has got complete possession of the outworks.

I have spoken of these sorts of fortification in the chapter that treats of field works, which, in my humble opinion, are more useful, more solid, less expensive, and more easily built than a variety of others that have been adopted to this day.

The demi-lunes or half-moons which are nearly mitred or crossed, and which I dispose between the counter-guards, have been constructed in that manner for the purpose of stretching as far as possible, beyond the body of the place towards the country. One essential advantage attends this method, which is, that the work being more spacious, it is better calculated to hold a greater quantity of artillery, and a large garrison; that it becomes double by means of the ditch, which separates it from the advanced work, which it covered as described above, and which is joined to the interior revetement by plain walls, separating a whole half-moon from it; in which space a small fort with loop-holes may be constructed to enable the garrison to dispute every inch of ground as the enemy advances. Under the main body of the place, I build a subterraneous chamber, to serve as occasion may require, either for a powder magazine, or for mines.

Between the half-moons and counter-guards, I construct another kind of ravelins, which are open towards the body of the place, cover the curtains of the counter-guards, and supply a double fire against the enemy and the covert way. These ravelins are not raised so high as the other works, in order to keep them under their fire; and I preserve a communication by means of palisaded caponnieres. I leave them empty within, that the besiegers may have as little ground as possible; they are moreover sufficiently thick and solid to withstand the discharge of ordnance, which can only batter in breach from the counterscarp, which acquires double strength, because by means of these works, it is enfiladed, and secured against the enemy’s attack or attempt to make a lodgment.

If the plan, which I had the honor of laying before the king of Sardinia, be carefully examined, it must be apparent to every military man, that the works I therein describe, are not only more useful, but capable of being constructed at a less expence, than those which are generally practised to this day. It will be clearly seen, that I have done nothing more than add some additional proportions of the flanks and bastions to the counter-guards, which are usually erected; and that I have augmented their double face, by joining it to the half-moons of the curtain. The object of this addition, is to throw obstacles in the enemy’s way, should he attempt to make close approaches, to cover the body of the place, to render the siege difficult, to increase the besieger’s expence, and to give confidence to the troops of the garrison, who are thereby no longer exposed, as they must be in all outworks erected upon the foot of the glacis.

It is not, however, my design to throw works of this kind into utter disrepute. There are situations and local circumstances, which not only make their adoption useful, but render it absolutely necessary. I cannot pretend to describe the specific nature of such exigencies, as they grow out of existing cases, which an able general and an engineer will know how to discriminate by examining the ground.

The ditch belonging to the body of the place, be its soil what it may, must be very broad, as the chief security to be derived from it, depends entirely upon its width. The enemy cannot easily fill it up, and he must suffer a considerable loss of men, should he attempt to cross it; being exposed to the discharge of artillery from the flanks, which artillery cannot be dismounted from any quarter or lodgment, before the counter-guards are taken. The storming of the place must depend entirely upon the previous conquest of the side ravelins, and of the centre half moons; for unless the enemy has first effected this, he will not be able to cross the ditch, or make any lodgment, since at every approach he must be annoyed from the flanks, and battered in front; he must, in fact, attack and get the better of five works at once. The execution of any part of so important a task, must be the more dangerous, because in proportion, as he overcomes one line of defence, another presents itself which is equally formidable, and the rest increase in difficulty and hazard.

When I submitted this new method to the consideration of able and intelligent men, only one opponent started to controvert the property of its general adoption. This was a celebrated Dutch engineer, who asserted that it could not be of any essential service, except in hexagons, or figures that had many sides; he further argued, that the method was more faulty in small works, because the angles became more acute, and that no use could be made of them in regular fortification.

I had the good fortune to satisfy this gentleman, and to convince him, that his objections were not well founded. I stated to him, that by increasing the width of the ditch at the angle of the flanks of the bastion, I reduced that angle to any size I judged necessary; I maintained, that by so doing I did not weaken the place; but that on the contrary by cancelling the parallelogram of the counter-guards, I rendered more oblique any battery which the enemy might erect in front of the bastion, whilst the rampart belonging to it fell under a cross fire from the mitred half-moon.

With respect to its uselessness in irregular fortification, after having discussed the subject at some length, I got him to agree with me, that every detached piece of fortification might be constructed any where (and with greater advantage to the ultimate defence of a place) sooner than in plain counter-guards, horn or crownworks, tenailles and such like fortifications, because by means of the retreat which was secured under a second line of retrenchment, by means of the regular resistance it afforded, without having one dead angle attached, and by means of the little ground it left for the enemy to lodge on, the main body of the place was more effectually protected, and the approaches of the enemy were considerably checked.

With regard to the construction proposed in this new method, I take all the measurements, and I mark all the essential points upon capital lines; that is to say, I prolong the lines of the saliant angles of the bastion, and those of the centre of the curtain; after which I determine the width of the ditch at 23 or 24 toises, in order to make the parallels of the faces of the different bastions for the counterscarp of the counter-guards and of the great half-moon, and finally the thickness of the works, to agree with the ditches in front.

With regard to the ravelins which are made between the mitred half-moons and the counter-guards, I place the saliant angle in the centre of the scite, and I construct faces to them in such a manner, that they are under a straight line of defence from the half-moons and counter-guards. I erect the counterscarp and glacis in the usual manner, only with this difference that I wish to have a ditch of moderate breadth and depth between the covert-way and the glacis: say, two toises broad upon two deep.

In order to clear the ditch of occasional rubbish that may fall in, or of pieces that may drop from the demolished parts of a fortification during a siege, square excavations or wells must occasionally be made along the flanks and faces of the different works; by which means the ditch is always kept clean, and you may at any time repair the fortifications, whilst on the other hand, the enemy, should he attempt to storm the place, must have recourse to fascines, as he could derive no advantage from the materials that would otherwise be found under the walls.”

This ingenious writer has described every part of the method proposed in a clear and perspicuous manner. His plan is particularly valuable, on account of the exact measurements it contains, whereby the most common understanding may become acquainted with the construction. He appears singularly anxious to have it practically proved, that works can be erected according to this method at a less expence than by any other, and that there is no comparison between the advantages it affords in point of real utility. In chap. 16, p. 61, the following account is given of his second system, which he calls the Great System.

“After I had thoroughly digested my plan, relative to the best method of covering a town or fortified place by outworks, it naturally occurred, that I had not provided the necessary means of keeping the troops under shelter, of securing a retreat to the artillery, which is always seized whenever a work is taken by assault, nor of furnishing a heavier discharge of ordnance and musquetry than the enemy could pour in. These important objects put my invention to work, and I directed all the faculties of my mind towards discovering a kind of fortification which might not only cover the body of the place, and by a new disposition of its relative parts communicate equally with every quarter, without there being any necessity to carry the heavy ordnance into the ditch; but likewise oblige the besieging enemy to increase his means of attack, and make extraordinary efforts. I necessarily saw, that the saliant angles of the bastions should be well covered, and that the strongest ought to be raised before the curtain belonging to the body of the place, in order to force the assailants to make their attack on a quarter from whence the concentrated fire of several works, presenting a wide front of artillery, would issue with considerable effect.

After having for several years, directed the whole of my attention to this specific object, and tried the result of my reflections upon paper by a variety of designs; I had the good fortune to discover a method, whose plan exhibits to the eye several pieces that are joined together by their different walls, and in front of which there are ditches covered in with beams and strong oak boards, and made bombproof by means of a sufficient quantity of earth that is spread upon the whole. So that it appears evident to me, that there is only one species of fortification, which affords the means of concentrating your line of defence from every quarter, and of lining the parapets with heavy ordnance. By means of this construction, the lines and glacis will be secured against any immediate approaches of the enemy, during which seasonable interruption, the artillery may without risk, be withdrawn and lodged in the interior work; a convenience which cannot be obtained in detached pieces, on account of the difficulty which always attends the first erection, or ultimate demolition of them.

By taking away the beams, or by destroying them at once, and by pulling down the walls which compose the flanks, you suddenly open a new work upon the enemy; which work has the advantage of being considerably larger than the one he has just attacked and taken, and against which he must raise fresh batteries, and prepare the means of crossing a ditch, he had not foreseen, and which he cannot easily pass. This work either communicates with a tenaille that commands it, or is connected with a horned work, flanked by two others of similar construction. The tenaille is open in the centre (being divided into two parts by a ditch) in order to leave as little room as possible for the enemy to lodge on, and to multiply the enfilading points of the place.

Between these large works, demi-lunes or half-moons, of three orders, are constructed in the shape of bastions. These have orillons and ditches between the two, which flank the side-works, and are always protected by an enfilade, that the enemy never can lodge without being exposed to a cross and rear fire. In order to cover the whole body of the place, I construct other intermediate demi-lunes, which are equal in elevation to the first works. These contribute greatly towards preventing the enemy’s approaches; for they not only enfilade the covert-way, but they likewise double the defences in such a manner, that the enemy, as has already been observed, cannot attack one place without experiencing a necessity to attack four others at the same time: to which may be added this disheartening circumstance, that as fast as he advances, so fast a retreat is made behind some new work, and he is, of course, obliged to recommence his attack.

The regular communication between the several works must be kept up by means of sleeping bridges, which are well supported underneath by strong beams or stakes. Those which form a part of the rampart must be covered with four feet of earth, well pressed together. The walls by which the works are connected, must be so built as to be easily demolished, and they must only serve to cover the subterraneous fortifications. These walls are never within the reach of the enemy’s cannon, and when they are pulled down, their ruins are thrown into wells, or excavations, which have been previously dug at the foot of the main wall, to prevent the ditch from being filled with them: subterraneous embrasures are opened from within to enfilade the ditch, and to obstruct the passage.

When by dint of perseverance, and after having expended considerable sums of money, lost many lives and consumed much time the enemy has at last obtained possession of these works, he discovers, that his sacrifices have only led him to an unexpected body of the place which he cannot injure. This new construction he finds flanked on both sides by two double bastions, and a broad curtain lined with a triple front of artillery, having a very wide ditch, traversed by tenailles, batteries from casemates, and defended by flanks with the two cavaliers belonging to the bastions, which keep up an incessant fire upon the artillery that is planted in the carried outworks, and render it almost impossible for him to establish a lodgment.”

“I need not pretend,” continues the same author, “to have discovered by this new method, any certain means of rendering a place impregnable; such an idea would be chimerical and absurd.

Let a town be ever so well fortified, that town, if properly invested and resolutely attacked, must eventually fall, unless it be seasonably succoured from without. My chief object is to correct the errors into which former writers seem to have fallen, and by the methods I have proposed, to harrass a besieging army, not only by increasing its expence, but by occasioning a considerable loss of men; I thereby prolong the siege, and gain time for the garrison, so that succours may arrive, or such conditions be entered into as will secure the country, which the place attacked is destined to cover.

Counter-guards, ravelins, and demi-lunes are, in fact, a species of fortification by which they flank one another obliquely, and which only tend to embarrass the troops of the garrison, whenever it is judged expedient to manœuvre under the fire of artillery; a circumstance that invariably causes confusion; whereas the works which I have proposed are capacious enough to admit of every movement and evolution without inconvenience.

Horned and crowned works are extremely expensive in their construction, and of little use when completed; their lines of defence, their faces and their flanks are so short and limited, that a besieging enemy can with great ease attack, and carry them by means of an equal front and range of fire: and when he has so far succeeded, he derives considerable advantage from having opened a wide space of ground on which he can erect angles to annoy and batter the place. Whereas in the works of my proposed method, the foundations are broader, the defences are more direct and within musquet shot, and when the garrison retreats towards the body of the place, the ground which it abandons is scarcely sufficient for the erection of a small battery; it is moreover exposed to all the retrenched and flanking points, so that the enemy would be instantly dislodged.

Tenailles and queues d’hirondelle contain dead angles which may always be taken advantage of by the besieging enemy. This does not exist in the works I propose. For at every approach, not only fresh expences must be incurred by the assailant, but he will remain exposed to several fires at once, without being able to cover himself from the reverse and cross ones.

Double ditches afford the means of creating perpetual uneasiness in the enemy, by uncovering fresh works as he advances. So that the siege is protracted, his expences are increased, and his loss of men, ammunition, stores, and artillery is proportionably multiplied.