Annals of a Fortress Part 24

Besides, these appendages have the further advantage of giving side views over the circ.u.mvallation itself and masking its foot.

This principle regulates and will always regulate attack and defence; distances alone modify its applications.

The more eccentric the defence is, the more distant must be the attack, and the wider the perimeter it must occupy; but it should be observed, that the more widely the defence is extended, the more open its flanks are to attack; these flanks therefore must also be capable of being defended, for every obstacle that offers only its own resisting force, without being protected by the action of a neighbouring obstacle, is soon destroyed.

Whether fortifications or plans of battle are in question, the same principle comes into play. "Every part should defend its neighbour and be defended by it." It is clear that the solution of the problem becomes more and more difficult in proportion to the enlargement of the range of projectile weapons, and the extent of fronts of fortification or lines of battle.

Vauban, and most of the engineers who were his rivals and successors, had resolved the problem in view of the range of the artillery of the period.

Suppose a hexagon (Fig. 79), fortified according to Vauban's first method, it is evident that all the parts of the circ.u.mference of one thousand, and even one thousand eight hundred yards, are commanded by the curtains, the faces of the bastions and the demi-lunes. If the fortress stands in a level country, the enemy cannot occupy any point in that circ.u.mference without being exposed to its fire.

To raise his first parallel and first batteries, he would have to begin his works at the limit of the range of the rampart guns; and, as we saw in Fig. 70, he must erect these batteries sufficiently near the place to enable their fire to tell upon the defences--_i.e._, at eight or nine hundred yards. At this distance the curtains could be swept, the faces and flanks raked, and the parapets thrown down. As the projectiles reached either point blank, or under an angle of about 10 when the ball rebounded, the besieged could protect himself against it for a very considerable time, and keep his own artillery intact.

[Ill.u.s.tration: FIG. 79.]

But as the range of siege pieces in the present day extends to eight or nine thousand yards, the conditions both for the besieged and the besieger are very different. Hence (Fig. 80) the enemy raises his batteries on two or three fronts of the circ.u.mference, taking advantage of the rise in the ground, a wall, or a wood to protect his works, and when all is ready, he unmasks these batteries, and covers a segment of the fortress with a quant.i.ty of explosive projectiles, which, reaching it at an angle of 25 to 30 burst, no matter where--_dans le tas_, to use a common expression--the distance not allowing an aim at flanks or faces in particular--the besieger being in fact unable to distinguish them. Supposing the besieged able to maintain his artillery and reply, exposed as he is to the deluge of iron on his face and flanks, he has to aim at eccentric points which may vary, to whose position he has no clue but the smoke of the guns, and at an enemy, who, taking advantage of an indefinite amount of s.p.a.ce to make his arrangements and shelter his men, is completely free. But to maintain his artillery and preserve his men and munitions, the besieged has only a s.p.a.ce relatively limited to move in; he is soon enc.u.mbered with _debris_ of all kinds, every movement is difficult for him, and he has not even room to repair damages. He tires himself out to no great purpose. If the attack has maintained its fire at a long range for several days, it has introduced such confusion into a great part of the defences, that in two or three nights afterwards the first parallel may be commenced at about one thousand yards, it may be well armed and protected by batteries _en retraite_ and trench-shelters, so as to discourage sorties and allow of an advance to crown the covered ways. In what state are the works of the besieged by this time? The flanks of the bastions are as much damaged as their faces, the demi-lunes are untenable, and the ditches partly filled up; disorder and confusion prevail on all sides. No breach is practicable, certainly; but all the works are seriously injured on three or four fronts, and at one thousand yards distance, a breach may be made, and that a wide one. The garrison may sustain the a.s.sault to the last, and sell the possession of the _debris_ of its work dearly; but in this case the final result is not doubtful.

[Ill.u.s.tration: FIG. 80.]

In proportion to the length of the trajectory, therefore, the defence must remove its defensive arrangement from the centre of the place.

[Ill.u.s.tration: FIG. 81.]

If each front of Vauban's defence was about four hundred yards in length, it ought to be from thirteen to fourteen thousand yards now (Fig. 81). That is to say, the side of the hexagon which was four hundred yards--_i.e._, from one salient of a bastion to another--should be fourteen hundred yards. Let A be the main body of the fortress--on a plain suppose; forts will be erected at B and C, the zone of action of each of these works being eight thousand yards, they will protect each other and cross their fires without the possibility of their projectiles falling into the fortress if any of them should be in the power of the enemy.

[Ill.u.s.tration: FIG. 82.]

Fig. 82 presents the block plan of each of those forts B and C, to whose interior arrangements we shall return. But by this excessive lengthening of the _capitals_, the forts B (Fig. 81), may be swept along the whole extent of the arc of a circle _a b_ (more than the third of the circ.u.mference); they occupy the points of a triangle, and if one of them were taken the enemy would be able to batter two of the forts C. It is therefore necessary, with an extended radius, to multiply the defences, and to enable them to protect each other in a more effective manner.

This is the method indicated in Fig. 83.

Here we have a dodecagon. The forts of the outer zone are seven thousand yards apart, and the works, A, flank each other; a second zone of forts B commands the latter, if required, and the zone of action of these second works extends beyond the outer line of forts. Railways are required to connect the forts of each zone, and to put them in communication with the body of the place.

This extension of the fields of defence may, according to the nature of the ground, be divided into two zones with a central nucleus.

[Ill.u.s.tration: FIG. 83.]

The interior zone would consist of permanent works, forming an _enceinte de preservation_; a line of forts at intervals sufficiently strengthened, in case of war, by field works.

The exterior zone would be fixed by occupying strategic points well chosen and considered beforehand, forming small camps protected by temporary works, and affording security to a numerous army, whose manoeuvres the enemy could not espy.

The expenditure entailed by such a system of defence is unquestionably enormous. But as respects this question there is to all appearance an unwillingness to realize exactly the new state of things produced by artillery of long range.

The expenditure involved in the successive systems of defence from ancient times downwards has been a continually increasing one. The wall built round Paris by Philippe-Augustus, would not cost, the running yard, as much as that of Charles V.; the latter, again, must have been less expensive than the bastioned fronts of Louis XIII., and these again would be far from necessitating the outlay (_i.e._ estimated by the running yard, and reckoning detached forts) occasioned by the fortification of Paris under Louis Philippe. Similarly the mounting of four or five trebuchets, and the movable towers required for attacking a fortified place before fire artillery was employed, cost less than the manufacture of the artillery used at the siege of Turin in 1535. The latter again would be far less costly than the French and English artillery at the siege of Sebastopol. Whereas at the time when smooth-bore guns were used a place might be attacked with about sixty pieces, five times the quant.i.ty are needed now; since it is necessary to operate over a much more extensive area.

War is therefore a game which tends to become more and more costly, and especially siege warfare. Are we then to conclude that nations will become disgusted with warfare on account of the frightful expense it involves? This is not probable.

At the present day, as in times past, that which costs most is defeat.

With forty millions well laid out in France, before the war of 1870, and from forty to eighty millions spent in the war itself, we probably should not have had to pay the four hundred millions which this war cost us, and we should not have lost two provinces which are certainly worth still more than that sum.

Parsimony in military preparations, in times of serious change, such as ours, is ruinous.

The principles to be followed may be summed up as follows: Commit yourself to no superfluous outlay, but spend all that is necessary.

Besides, is it after all certain that a good system of territorial defence is so costly as some allege?

Is it a question of building something like a Chinese Wall on our eastern frontier? Is it likely that if a few strong positions rendered impregnable without unnecessary works enabled us to keep an army of observation two hundred thousand strong, secure from any surprise in the elevated valleys bounded by the ranges of hills which stretch from the Jura along Belfort, Remiremont, Epinal, Langres and Dijon, and border the right bank of the Saone as far as Lyons, the Germans would be in a hurry to make their way a second time to Paris? If they experienced the slightest check on such a route, if they were obliged even to halt, what would become of them?

The essential consideration therefore is a good choice of positions; shelter from the approach of an invasion on the flanks, and the avoidance of enormous expenditure in the attempt to defend all points.

Let us suppose that Metz had been rendered impregnable, or at least so provided with defences that it could have held out for six months; and certainly the thing was possible. In the first place we should not have lost that town, and secondly the war, notwithstanding our deficiencies in soldiers and in artillery, might have taken quite another turn.

Greater sacrifices on the part of the enemy, more prudence, and a still greater loss of men, would have been required to constrain us to a peace accepted before the cannon's mouth.

War is made now a-days with armies a million strong; this is all very well while the invading force meets no very serious obstacle, either in front of it or on its flanks; when the combinations which such a vast display of forces necessitates are not disturbed at any point, and when the strategic operations upon the ground succeed each other with perfect precision, as one might trace them on a map in our studies. But these enormous agglomerations of men could give rise in a single day to appalling perils, after a grave check on one of their flanks. Such ma.s.ses can be advanced, fed, and manoeuvred only by means of a very complicated, and therefore delicate and easily deranged machinery. The Germans a.s.serted that by the possession of Alsace and a part of Lorraine we had a hold upon Germany. Now their country is almost dove-tailed into France. The future will show whether that will greatly benefit them.

In 1870 and 1871 we saw what could be accomplished by the little fortress of Belfort; which was perhaps the only one among our strong places possessing guns of long range, and a garrison well commanded and determined to defend itself.

It persisted in maintaining the offensive over a circle of from twelve to sixteen miles, thanks to a few rifled cannon with which the ramparts were furnished, and which protected sorties through a radius of three to four miles. For a month it hindered the planting of siege batteries; and, in spite of a bombardment of seventy-three days, the town had only four of its houses burned. This defence is instructive, and shows that the old defensive system has had its day.

During the siege the batteries of the besieged hardly suffered at all, and had recourse to indirect firing--that is, they fired over the barracks from the gorge of the castle without seeing the mark, but regulating by observation. This indirect firing, which took no account of the plan of the crests of the defence, and which thus enabled a powerful fire to be directed to any point, without regarding the faces, produced a great effect on the batteries of the enemy, who, on his side, could not see these guns, and did not know how to regulate his fire.

The question, therefore, remains undecided; and, though a long range enables the attack to envelope each work more decidedly with its fires, each battery of the besieger may be subjected to the fire of a greater number of guns by the defence. At Paris, the forts which are by no means planned in view of the present long range, enabled a weak and inexperienced garrison, whose _morale_ was none of the firmest, to execute sorties with success to a distance of two miles and a half.[65]

With good troops, then, we might have raised in one night, works which would have enabled us to resume the offensive, and to push further on, to break the line of contravallation, and seriously to embarra.s.s the besieger. It is not therefore proved that long ranges give a greater advantage to the attack than to the defence, while, on the other hand, the long range of rifled cannon may be affirmed to be favourable to the defence; but it would be so only on the condition of the works being planned in view of the new action of artillery, and not according to old traditions, however glorious. The destructive power of explosive projectiles puts obstacles in the way of the besieger's approaches; and, in fact, during the late war we never saw employed that old mode of approach with a view to attacking by breach and crossing the ditch.

The Germans were not so stupid as to employ these cla.s.sical methods.

They took up their position on favourable and often commanding points, at three thousand eight hundred to four thousand two hundred yards around our fortresses, which adhered to the old defensive system adapted to ranges of two thousand two hundred yards at most; and covered with sh.e.l.ls our works and the towns they were supposed to protect, without risk to a single sapper. We thought that odious and unreasonable; like those n.o.bles of the fifteenth century, who thought it an abominable shame that their feudal nests should be breached with bombards, and declared that the trade of war was thereby damaged. But suppose we should some day condescend to practical consideration, when these old flanked fronts fall into disesteem, and the new generation of military engineers determine to admit that we have to do with artillery of long range, and to take advantage of the fact, a certain degree of superiority might be doubtless given to defence over attack.

How ought these isolated forts, which are destined to replace the salients of our old fortresses, to be planned? They should afford ample s.p.a.ce for a large number of fires--even indirect fires--in case of need; consequently extended faces and short flankings--that is, as shallow as possible, and perfectly open gorges. They should efficiently protect the works of counter-approach, and consider defence at close quarters as a question of only secondary importance; for very seldom would there be occasion for it, if indeed the case ever presented itself, which is doubtful.

[Ill.u.s.tration: FIG. 84.]

Referring to the general defensive system shown in Fig. 83, and required the plan of one of the forts, A, the result will be Fig. 84, giving the work at the lower level at C, and at the level of the batteries at D.

The counterscarp should be cased up to at least sixteen or seventeen feet above the bottom of the ditch.

The escarp should be made with tipped earth. The masonry works should all be covered and secured from being enfiladed; they form casemates inside E. Beneath the terracings, powder magazines, F, and the pa.s.sages communicating with the _oiseaux_ or lower _orillons_, G, protected by the counterscarp and the covered way, and which are used only if the enemy attempts to pa.s.s the ditch. The faces and flanks on the outside are planned on angles sufficiently obtuse to cross their fires. The two faces in the plan (Fig. 84) may be armed with eight guns and the flanks with six guns. This work is separated from that of the gorge by a traverse that efficiently protects this gorge, which possesses its flanks, armed with four guns and its orillons.

From the work of the gorge is a communication into the fort by a covered caponniere, forming traverse in the direction of the _capital_ or centre line. The gorge is defended by a curtain for the riflemen, and, at need, for small pieces of artillery. At need also, on the terre-plein of the work of the gorge may be mounted guns of long range, affording an indirect fire in the circ.u.mference of a semi-circle, over the great traverse H, if the parapets of the faces are damaged by the fire of the enemy.

Fausse-braies consisting of palings are fixed in the ditch at ten feet from the base of the escarp, to hinder the fallen _debris_ of the escarp from filling up the ditch, and to enable its pa.s.sage to be defended. The well-covered internal masonry works prevent the acc.u.mulation of earth on the interior platforms, and afford casemates, which enable the garrison to take rest in perfect security; at any rate along the two faces and the great traverse. Blindages can be set up on the traverses of the batteries, and can be easily repaired every night, as well as the escarp of tipped earth.

It would be difficult to say how many projectiles it would require to render such a work untenable; since we have seen in the siege of Paris, that a marine battery erected on tipped earth on the military road between the forts of Rosny and de Noisy, armed with three guns, had been a mark for the German sh.e.l.ls during twenty-four days, without any of its guns having been dismounted, or its escarp suffering more than could be made good each night.

Permanent works should, however, only be established with the utmost circ.u.mspection:--1. Because they require a very considerable outlay. 2.

Because they are necessarily familiar to, and for a long while studied by the enemy, who takes his measures accordingly.

The important point is to possess an accurate acquaintance with the ground to be defended, and only to establish permanent works in second line, and on points incontestably favourable for defence, supposing an artillery of even a still longer range than the present.

Every centre to be defended should therefore possess works sufficient to prevent a surprise; and in addition at a distance of six to eight thousand yards, a line of forts, crossing their fires if possible, or at any rate connected by strong batteries; and lastly, at a distance of about four thousand yards, positions previously examined and known, suitable for placing very simple works of field fortification, but which at a given moment may offer a resistance sufficient to permit movements on a grand scale--and delay the formation of an enemy's batteries.

[Ill.u.s.tration: FIG. 85.--DEFENSIVE SYSTEM OF THE GREAT INTRENCHED CAMP.]