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sed, but ular half : to conefended; at cover, le square iangular, bastions y advanne as in the sides than 200 e within im. The wice, by ed. vering a ring the t, either ntry, or strength 1 accord- you fix ; 1. The h it is to , during t up; for try movesequel of eadth and the tête de kewise, the $: 3. Wherted by musy artillery only, ver has only one in this case, what nd the form of the If, so that you may ertainty, the defensive i be made to the greatest 1 you are to construct a tête ng the retreat of an army, or nt, you ought to consider, wheI to their composition and the that retreat is likely to be exe
or slowness; whether there 1 retreating troops will lie
ments, should an attack be expected; in this since it is very difficult, not to say impossible, case, it will suffice to regulate the size of the to give a general rule of computing the necesredoubt in such a manner that the number of sary length of the interior sides of redoubts acmen intended for its defence can man the para- cording to the strength of the detachments, and pet properly, without being crowded and ob- that trying is the only way.' This author's work, structed in their motions; but if the garrison is however, in which he has collected and generally to reside in the work, its interior surface must be exposed with perspicuity, most of the modern larger.
principles on which field-fortification is groundVarious methods have been proposed for cale ed, deserves no small degree of praise. culating the necessary length of the interior M. Malortie de Martimont proposes the folsides of a redoubt, according to the strength of lowing rule, supposing the redoubts to be square, its garrison; but most have the double defect of and that the garrison is to reside within them :not being applicable to small detachments, as 1. Multiply by ten the number of men of the redoubts would then be considerably too which the detachment is composed, and the little, and to increase beyond measure the in- product will give, in square feet, the necessary terior surfaces of those works, when their garri- extent of the surface contained between the foot son exceeds a certain number of men.
of the slopes of the banquettes. The method proposed by Noizé de St. Paul, a 2. Extract the square root of that product to French engineer, is better in general than any one decimal, and it will give in feet and tenths we have seen. We shall observe, however, that of a foot, the lengths of one of the sides which it is rather complicated, as it varies according to enclose the above-mentioned surface. the strength of the detachments ; it contains, 3. Add to this length twice the number of besides, several inaccuracies; we point out the feet which the base of the interior slope of the two following:
parapet, the breadth of the banquette, and the This author says, No. 32, page 39, of his base of its slope, are to have, and the sum will work on field-fortification, if the detachment be the length, in feet and tenths of a foot, of one which you intend to place in a redoubt, is com- of the interior sides of the redoubt. posed of more than ninety men, and does not Let us suppose, for instance, that you have to exceed 120, tako Chie-fourth of the number o? construct a square redoubt abc d, plate VI. fig. 4, men for a reserve, which you may make equal to for ninety men: multiply ninety by ten, and one-third of that number, if the detachment the product 900 will show that the surface ik lm, consists of 130 men or thereabout: then divide which is contained between the foot of the the remainder by eight, and the quotient will slopes of the banquettes, ought to be 900 square give the length in toises, &c., of each interior feet : extract the square root, thirty, of that proside.'-According to this rule, a detachment of duct for the length of feet in the side i k, which 109 men requires that the length of the interior is represented by a b in the profile fig. 5. Now si les should be nearly nine toises and three supposing the base of the slope c of the banfeet; whereas it is proved by experience, that quette to be six feet, the breadth of the bancight toises and three feet, or thereabout, are quette d three feet, and the base of the interior enough; thus Noizé de St. Paul's rule increases, slope e of the parapet one foot; multiply the without necessity, the size of the redoubt, which sum of those dimensions by two, and add the requires thereby more time, and a greater quan- product twenty to the square root thirty which tity of materials for its construction :—besides, you have found before ; then will the sur fifty the author is inconsistent with himself; for he he the length in feet of the interior side e e fig. 5, says, p. 44, note k, in the same work, that a and e f fig. 4. It is evident, that in all redoubts detachment of 100 men requires a redoubt, constructed by this simple method, every man of whose interior sides should have from eight to the detachment has for himself ten square feet nine toises at most. But let us proceed further, of the clear surface which is contained between and suppose that the detachment consists of 120 the foot of the slopes of the banquettes; and men; according to the same rule, the interior ten feet, in addition to the space afforded by the sides of the redoubt should be eleven toises one banquettes and their slopes, as this writer confoot and six inches : but Noizé de St. Paul re- tends, will suffice in all redoubts, let their size commends the same length for those of a redoubt and figure be what they may. constructed for 180 men; since he says, p. 39, Square redoubts are more simple and easy * if the number of men exceeds 150, as they will construct than any other; but the configuration be able to man in two ranks the parapet of a of the ground, and the number and situation of redoubt capable of containing them, the length the points which a redoubt may have to defend, of the interior sides will be found by dividing &c., frequently require that its figure should not the detachment by sixteen. Now, why should a be square; in this case, plant staves at all the redoubt, calculated for 120 men, be exactly of points, where, in your opinion, the vertex of the the same size as a redoubt constructed for 180 ? angles, formed by the interior sides of the work, And is it not evident, that Noizé de St. Paul's can be placed to the greatest advantage; and method, which may give satisfactory results in after taking, with the plain table, or by any some other instances is very defective in these other means which you have at hand, the plan of two? Indeed it appears that he was aware of the figure delineated by lines which you suppose its insufficiency with regard to certain detach- to join those staves, consider it as representing the ments; for he says, No. 32, p. 40, that he interior contour of the parapet : 'measure the proposes it as a scale of comparison, which angles formed by those lines, in order to ascershould be used merely as a guide in practice, tain whether they are sufficiently open, Max. 1,
and if some are not, rectify them : inside of the in such cases, to construct a sinall fortress, esplan draw a parallel to its outline, and at a pecially if you have guins to use. Star forts are distance from it, equal to the number of feet seldom constructed either in the triangular or which you intend to allow to the base of the square form, a redoubt being almost always preinterior slope of the parapet, the breadth ferable to either. In a triangle there can be no of the banquette, and to the base of its brisures, in a square their angles are 150°. stope: and, as the figure described by this A pentagon is somewhat superior to both, the parallel represents that of the space which is defence of its saliant angles being better, and the contained between the foot of the slopes of the angles of the brisure 132°. The hexagon is still banquettes, compute its area in square feet; if better than the pentagon, though its saliants are it appears from your calculations, that the re- by no means well defended. The heptagon has doubt will be considerably too large, according saliant angles of 1280, and those of the brisures to its garrison and artillery, this defect may be 112. This form might therefore be used with remedied by shortening the interior sides, or considerable advantage, were the construction diminishing their number when it exceeds four, not difficult; the most convenient, however, as or by giving a smaller opening to the angles: well as the most advantageous polygon for works but, if the work is small beyond measure, the of this kind, is the octagon. The construction is contrary should be done.
made either upon the interior polygon, by placShould a redoubt be circular, compute the ing equilateral triangles on its sides, or on the radius of the circle, bounded by the foot of the exterior side, by means of the perpendiculars slope of the banquette, so that the enclosed sur- from the saliant and re-entering angles. face may allow ten square feet to each man, and Bastion forts have often been proposed, but 324 square feet to each piece of cannon : add are inferior to star forts; the triangular half to this radius twice the base of the interior slope bastion particularly. They are difficult to conof the parapet, twice the breadth of the ban- struct; the saliants are too acute and ill-defended; quette, and twice the base of its slope ; then the faces of the demi-lunes are without cover, drive a picket at the centre of the redoubt, and and the interior surface is too small. The square fasten to it one end of a cord equal to the radius half-bastion is little better than the triangular, thus increased; and with the other end, to which but it encloses a larger space. When the bastions a pointed picket is fastened, describe a circum- are full, the work may sometimes be very advanference upon the ground.
tageous, and the construction is the same as in To ascertain how many men and guns a re- permanent fortification. In bastion forts the sides doubt which is constructed can contain :-Com- should not be less than 100, nor more than 200 pute the area in square feet of the surface con- yards, that the flanked parts may be within tained between the foot of the slopes of the musket shot : 130 yards is a good medium. The banquettes, and divide it by ten if no artillery is best form of the curtain is to break it twice, by to be placed in the redoubt; the quotient will which a very advantageous fire is obtained. give the number of men that can be lodged in Têtes de pont are thrown up for covering a the work : but, should the redoubt be supplied communication across a river, and favoring the with cannon, subtract 324 square feet for each movements of an army or detachment, either piece from the above area, and divide the re- when advancing into the enemy's country, or mainder by ten, which will give the number of retreating from it. The form, size, and strength
of a tête de pont, ought to be regulated accordOf fortins or field-forts.—Two kinds of fortins ing to various circumstances, and before you fix or field-forts are most generally used, when the upon them it is necessary to consider; 1. The ground, the intended object of the work you importance of the communication which it is to have to construct, and the strength of its detach- cover, and the probable length of time, during ment, will allow you to make it regular, or nearly which the communication is to be kept up; for sa; these are the forts with tenailles or star-forts, its utility may be confined to a temporary moveand the forts with bastions; but sometimes you ment of the troops, or extended to the sequel of are compelled to construct a fort which is com- operations for a long time: 2. The breadth and posed of different figures at once, and in this form of the river at the point where the tête de case no particular name can be given to it. pont is to be thrown up ; and, likewise, the
Field-forts take a particular name also from nature of the country on both banks : 3. Whetheir number of saliants; thus, a fort is said to ther the tête de pont can be supported by musbe square, pentagonal, or hexagonal, &c., ac- ketry from the opposite banks, or by artillery only, cording as it has four, five, or six saliants. or by neither; 4. Whether the river has only one
Star forts, or forts à tenaille, are such as form arin, or forms an island; and in this case, what a regular suite of saliant and re-entering angles. is the breadth of its arms, and the form of the They are, in fact, polygons, whose sides are ground in the island itself, so that you may broken so as to form the re-entering angles. If determine, with more certainty, the defensive possible, the saliant angles should never be less dispositions which can be made to the greatest than seventy degrees, and the nearer they ap- advantage: 5. When you are to construct a tête proach to ninety the better, as a rectangular de pont for covering the retreat of an army, or defence is always the best. The brisures, or strong detachment, you ought to consider, whefaces, forming the re-entering angle, should not ther, according to their composition and the be less than fifty feet, or more than 100. If they state of things, that retreat is likely to be exeare longer they require a numerous garrison cuted with celerity or slowness; whether there to defend them, and it would therefore be better, is any fear that the retreating troops will be
closely followed up ly considerable forces, or and d e, the direction of which ought, in general whether they can retire quietly, and without to be as perpendicular as possible, toe f and df, being exposed to any attack which may endanger which they defend. Care must be taken, howthem: 6, and lastly, you ought to examine what ever, that they are not exposed to be enfiladed, is the strength of the army, or detachment, its which depends, of course, on the configuration number of cannon, the quantity of stores, and of the river, and the disposition of the surroundequipage, &c., and regulate accordingly the size ing ground. of the tête de pont, as well as the passages Sometiines, also, a tête de pont may be comthrough it, in order that the whole may file offposed of a horn work, the inside and branches without stoppage and confusion; all these va- of which are defended by batteries a, erected on rious circumstances oblige us to make a differ- the opposite bank. When the ground does not ence in the siz", form, and strength of a tête de allow you to construct these batteries, the pont. If an army or considerable detachment, branches of the born work may be broken. for instance, is closely pursued by a great force, Half a square fort, with bastions, makes a and can retreat but slowly, either on account of strong tête de pont, particularly when you can its composition, or because it is compelled construct on the opposite bank batteries and to take particular precautions, which require intrenchments. Half a star-fort, or redoubts so tine, the tête de pont, which is intended to disposed as to Aank each other, may also be favor its passage across the river, ought to be of used for a tête de pont. a certain extent, and capable of making a good Of intrenchments of armies.—The whole of defence; for then, not only the troops, artillery, the works and obstacles by which an army or a &c., must tile off through it without any oh- considerable body of troops cover theinselves, struction or confusion, but it ought to check the for their own defence, may be called intrenchenemy, should he attempt to approach it: on the ments of armies. In general the object is, to incontrary, if a tête de pont has to cover a com- terpose between themselves and the enemy a demunication of no great importance, or the passage fensive line, whose protection may compensate across a river, of an army or detachment which for their inferiority in number; this line may be is not closely pursued, and can retreat quietly composed of parts so connected together, that and speedily, it will not require as much extent no uncovered space is left between them, in and strength as the former,
which case it is called a continued line; or The bridge or bridges, which a tête de pont those parts may be isolated from each other, and covers, should be concealed as much as possible uncovered intervals left between them; and then from the enemy's sight, as he would baiter and it is named a line with intervals. ruin them with his cannon; and that, in general, Intrenchments of armies can seldom be comthe most advantageous points for construct- posed of regular and similar works, nor even of ing those works are where the river bends in- works different in their nature, but symmetrically wards.
disposed, and so constructed, that all those of When a tête de pont is to cover only a com- the same kind may have the same dimensions; munication of no great importance, and across a for, on account of the ground, or because of a small river, a simple redan will suffice: provided, necessity to direct more fire to certain points however, that the river is so shaped as to prevent than to others, some irregularities will be rethe enemy perceiving the bridge from some quisite; thus it is impossible to foresee all the point; but, if he can perceive it, a piece should variations that may occur in the tracing of inbe constructed, whose flank defends the ground trenchments of armies; wherefore no particular from which the bridge can be seen. These rules can be given for every case; there are, small têtes de pont will acquire a greater however, general principles which ought to strength, if the ground on the opposite bank guide an engineer. ailows us to construct small redans where fusi- The works most commonly used for intrenchleers are placed ; these redans ought to be dis- ments of armies, in a continued line, are redans, posed in such manner, that their fire, after tenailles, or queues d'hironde, cremaillères and grazing the faces of the tête de pont, may cross bastions; hence intrenchments take the name of in front of the saliant, and as near to it as pos- intrenchments with redans, intrenchments with sible; the redan is intended to graze the flank of tenailles, or queues d'hironde, intrenchments
with cremaillères, and int nents with basWhen the river is so broad as to prevent the tions; sometimes also lunettes are placed in musketry fire of the redans doing any execution front and to a certain distance from a main infor the defence of the tête de pont, batteries may trenchment, which is then called intrenchment be constructed and disposed in the same manner
with lunettes. as the redans.
For the detailed construction of these works, A tète de pont which is intended to cover a we must refer the reader to the professional pubcommunication of importance, and necessary lications on the subject. for the movements of large bodies of troops, The following general principles should be requires a greater extent and strength than the observed, as much as possible, in the formation preceding. That represented by fig. 6, plate l'I. of intrenchiments of armies. is capable of making a good defence, particularly 1. Their flanks must be supported, and not when it can be supported by batteries a, placed exposed to be turned; for, of what avail would on the opposite bank; its outline does not differ be the defence in front which intrenchments widely from that of a redan, except that the faces afford, could they be attacked in the rear? are broken, in order to procure the two flanks b c 2. Their extent should be proportionate to the
strength of the army which they cover, since ployed; and, as it can scarcely execute any they are to be defended hy it.
movements outside of them, it is reduced 10 3. In tracing those intrenchments, you ought defend passively, if I may use that expression, tho lo avail yourself of every natural accident of works which cover it, and are sometimes very imthe ground which they traverse; a low and perfect: 3dly, a line with intervals requires less marshy spot, a stream whose banks may be labor than a continued line; therefore, the works overflowed, a ravine, a wood where an abatis which compose it can be constructed with greatmay be formed, and other natural obstacles, fre- er care in the same time, and with the saine quently afford great advantages, when properly number of workmen. Lastly, the former line is connected with the other defences; either by in- more easily adapted to the ground than the latcreasing the strength of some parts of the line, ter; as the engineer, who is not confined to a or, when they suffice to stop the assailants, by fixed tracing whose parts must all be connected, saving you the time and labor, which, without can place the works at the most essential parts of them, the construction of works would require. defence.
4. The line formed by intrenchments of In the late continental wars frontiers of counarmies should occupy, as much as possible, the tries have been the frequent objects of attack and elevated parts of the ground which it crosses, defence. They constitute important objects of and border the summits of the heights or hills in field fortification. M. Malorti furnishes some its direction; by which means the intrench- excellent directions for forming the principal ments will have a superiority over the assailants, works of this kind. who cannot approach them without passing i. Of lines of frontiers.—The works and obthrough uneven and difficult ground.
stacles disposed along some open parts of a fron5. Every point of the ground, in front of an tier, to shut up the country from one place, or intrenchment, must be seen and defended by post, to another, are called lines of frontiers. some of its parts.
These lines may answer very useful purposes ; 6. The habitations in front of the line should first, they protect the army which defends the be occupied and fortified, when they are suffici- country behind them, and also to secure its ently near to be supported by it; but should movements; secondly, they prevent the incursions they be too distant, and so situated as to conceal of the enemy's parties, and the devastation which the movements of the enemy, they must be de- they would occasion; thirdly, they remove the stroyed.
fears of the inhabitants, who then attend to agri7. For the same reason, a wood, which the culture. Lastly, they connect the defences of the line can support, must be occupied; but should frontier, and therefore increase the resistance its distance prevent it, and its situation be such which can be made. Indeed, a line of frontiers as to conceal the movements of the assailants, it will not afford those advantages, unless it be conrequires to be cut down.
sidered in its proper light and used accordingly; 8. The line ought to cover ali the habitations for should the army consider it, as forming its in its direction, so as to make them serve as own intrenchments, and actually defend it, as points of support, and to reap advantage from lines of frontiers have in general a greater extent their reverse fire.
than is proportionate to the strength of the army, 9. The number and strength of the respective it follows that the troops would be weak every works, depend on the greater or less danger to where; and that they would undoubtedly be which the part of the line where they stand may crushed by the columns which the enemy would be exposed ; if, for instance, the enemy could march to several points at once; thus the line scarcely approach it, and should he not be able would be disadvantageous rather than useful; to bring his cannon against it, the works thrown but on the contrary should the army support it up for its defence, would undoubtedly not re- only with a limited number of troops, and ocquire the same extent and strength as they cupy a position behind, from which it could rewould, in case the assailants could easily ap- pair rapidly to all points, and take in flank the proach and batter it.
enemy's columns when they begin to advance, 10. All obstacles which may obstruct the no doubt can be entertained, in this case, of the communications of the line, with such parts in utility of the line, and particularly when its its front as must be protected by it, or which extent is not so great as to preclude the army may impede the retreat of the army, should the from the possibility of supporting all its parts ; intrenchinents be carried, must be removed. for the enemy will be compelled to form partial
Intrenchments with intervals are now pre- attacks, and therefore to weaken bimself by diferred to those which form a continued line. viding his forces. The following are the general The following are the reasons which are assigned rules to be attended to, in the construction of for it; 1st, the former require less troops for lines of frontiers. their defence than the latter ; so that, with an 1. They require, like intrenchments of armies, equal number of men, a greater force can be that the extremities should be supported, and placed at the most exposed points, or stronger not exposed to be turned. Should a line of fronreserves kept; 2dly, the intrenched army can tiers be very extensive, it must be directed from form in such order as will not impede its move- one fortress to another, when there are any on ments; wherefore it will be able to pass succes- the frontier. sively from the defensive to the offensive, and 2. Their front ought not to present any unvice versa, according as circumstances may re- protected openings, by means of which the enequire : whereas, on the contrary, an army placed my may penetrate into the country which they behind continued intrenchments must be de- are intended to cover. The reason is evident,