Book: Elements of Military Art and Science

H >> Henry Wager Halleck >> Elements of Military Art and Science




Coehorn was followed in Holland by Landsberg, an able and practical
engineer, who to much reading added extensive experience, having himself
served at sixteen sieges. His system was in many respects peculiar, both
in trace and relief; it dispensed with the glacis, and all revertments
of masonry. His plans could be applied only to marshy soils. The first
edition of his work was published in 1685.

But the career of Vauban forms the most marked and prominent era in the
history of fortification; it constitutes the connecting link between the
rude sketches of the earlier engineers, and the well-established form
which the art has since assumed. In his earlier works we find many of
the errors of his predecessors; but a gradual change seems to have been
wrought in his mind by reflection and experience, and these faults were
soon remedied and a new and distinct system developed. Vauban has left
no treatise upon his favorite art, and his ideas upon fortification have
been deduced from his constructions, and from detached memoirs left
among his papers. The nature of his labors, and the extent of his
activity and industry, may be imagined from the fact that he fought one
hundred and forty battles, conducted fifty-eight sieges, and built or
repaired three hundred fortifications. His memoirs, found among his
manuscript papers, on various military and political subjects, are
numerous, and highly praised even at the present day. But his beautiful
and numerous constructions, both of a civil and military character, are
real monuments to his genius. The best illustrations of his principles
of fortification occur at Lille, Strasbourg, Landau, Givet, and
Neuf-Brisack. His writings on mines, and the attack and defence of
places, are, by the profession, regarded as classic. His improvements in
the existing method of attack gave great superiority to the arms of his
countrymen, and even enabled him to besiege and capture his rival
Coehorn, in his own works. He died in 1707, and was soon succeeded by
Cormontaigne.

The latter did not attempt the introduction of any new system, but
limited himself to improving and perfecting the plans of his illustrious
predecessors. His improvements, however, were both extensive and
judicious, and are sufficient to entitle him to the place he holds as
one of the ablest military engineers the world has ever produced. His
works on the subject of fortification, besides being elegantly written,
contain the most valuable information of any works we have. His most
admired constructions are to be found at Metz, Thionville, and Bitche.
The beautiful crown works of Billecroix, at Metz, are perfect models of
their kind. Cormontaigne died in 1750.

Cotemporary with him were Sturin and Glasser. The former deviated but
slightly from the systems of his predecessors, but the latter invented
several ingenious improvements which gave him great reputation.

Next follows Rosard, a Bavarian engineer; and Frederick Augustus, king
of Poland, who devoted himself particularly to this art. The former
casemated only the flanks of his works, but the latter introduced
casemate fire more extensively than any one who had preceded him.

In France, Belidor and De Filey published about the middle of the last
century. They were both able engineers but their systems were inferior
to that of Cormontaigne.

In 1767 De la Chiche introduced a system of fortification in many
respects original. He raised his covered-ways so as to conceal all his
masonry, and casemated a great portion of his _enceinte_. For exterior
defence, he employed direct fire from his barbettes, and curvated fire
from his casemates; the direct fire of the latter secured his ditches.

Next to De la Chiche follows Montalembert, who published in 1776. He was
a man of much experience and considerable originality, but of no great
ability as an engineer. Most of his ideas were derived from De la Chiche
and the German school of Rimpler. His plans have generally been rejected
by his own countrymen, but they still have advocates among the Germans.

General Virgin, a distinguished Swedish engineer, wrote in 1781. His
idea of strongly fortifying the smaller towns to the comparative neglect
of the larger cities, constitutes one of the principal novelties in his
system.

In 1794, Reveroni devised a system in which the casemates of
Montalembert were employed, but his guns were so arranged as to be
employed in barbette while the besiegers were at a distance, and
afterwards to be used for casemated fire. The casemate gun-carriage,
which formed a part of his invention, was ingenious, but never much
employed in practice.

Bousmard, a French emigrant, published in 1790. He adopted the general
trace of Vauban, but introduced modifications in the details essentially
different from those of Cormontaigne. Some of these modifications are
very valuable improvements, while others are of a more doubtful
character. Bousmard is, on the whole, a very able writer, and his works
should be found in the library of every military engineer.

Carnot's celebrated treatise was published in 1810. He was evidently a
man of genius, and during his career at the head of the War Department
of France, numerous and very important improvements were made in the
several branches of the military art, and especially in strategy. His
work on fortification exhibits much originality and genius, but it is
doubtful whether it has very much contributed to the improvement of this
art. His ideas have been very severely, and rather unfairly criticised
by the English, and particularly by Sir Howard Douglas.

Chasseloup de Laubat early distinguished himself as an engineer of much
capacity and talent. He followed Napoleon in nearly all his campaigns,
and conducted many of his sieges. He remodelled the fortifications of
Northern Italy and of the Lower Rhine. He published in 1811. The
improvements which he introduced are numerous and valuable, and he
probably contributed more to advance his art, and to restore the
equilibrium between attack and defence, than any other engineer since
Cormontaigne. After the fall of Napoleon and the partition of his
empire, the allies mutilated or destroyed the constructions of
Chasseloup, so that, it is believed, no perfect specimen of his system
remains.

The cotemporaries of Chasseloup were mostly engaged in active field
service and sieges, and few had either leisure or opportunity to devote
themselves to improvements in permanent fortification.

Choumara published in 1827. His system contains much originality, and
his writings give proof of talent and genius. He has very evidently more
originality than judgment, and it is hardly probable that his system
will ever be generally adopted in practice.

The Metz system, as arranged by Noizet, as a theoretical study, is
undoubtedly the very best that is now known. It, however, requires great
modifications to suit it to different localities. For a horizontal site,
it is probably the most perfect system ever devised. It is based on the
system of Vauban as improved by Cormontaigne, and contains several of
the modifications suggested by modern engineers. It is applied in a
modified form to the new fortifications of Paris.

Baron Rohault de Fleury has introduced many modifications of the
ordinary French system in his new defences of Lyons. We have seen no
written account of these works, but from a hasty examination in 1844,
they struck us as being too complicated and expensive.

The new fortifications of Western Germany are modifications of Rempler's
system, as improved by De la Chiche and Montalembert. It is said that
General Aster, the directing engineer, has also introduced some of the
leading principles of Chasseloup and Carnot.

The English engineers have satisfied themselves with following in the
track of their continental neighbors, and can offer no claims to
originality.

Of the system of fortification now followed in our service we must
decline expressing any opinion; the time has not yet arrived for
subjecting it to a severe and judicious criticism. But of the system
pursued previous to 1820, we may say, without much fear of
contradiction, that a worse one could scarcely have been devised.
Instead of men of talent and attainments in military science, most of
our engineers were then either foreigners, or civilians who owed their
commissions to mere political influence. The qualifications of the
former were probably limited to their recollection of some casual visit
to two or three of the old European fortresses; and the latter probably
derived all their military science from some old military book, which,
having become useless in Europe, had found its way into this country,
and which they had read without understanding, and probably without even
looking at its date. The result was what might have been anticipated--a
total waste of the public money. We might illustrate this by numerous
examples. A single one, however, must suffice. About the period of the
last war, eight new forts were constructed for the defence of New York
harbor, at an expense of some two millions of dollars. Six of these were
_circular_, and the other two were _star forts_--systems which had been
discarded in Europe for nearly two thousand years! Three of these works
are now entirely abandoned, two others are useless, and large sums of
money have recently been expended on the other three in an attempt to
remedy their faults, and render them susceptible of a good defence.
Moreover, a number of the works which were constructed by our engineers
before that corps was made to feel the influence of the scientific
education introduced through the medium of the Military Academy--we say,
a considerable number of our fortifications, constructed by engineers
who owed their appointment to political influence, are not only wrong
in their plans, but have been made of such wretched materials and
workmanship that they are already crumbling into ruins.

A fortification, in its most simple form, consists of a mound of earth,
termed, the _rampart_, which encloses the space fortified; a _parapet_,
surmounting the rampart and covering the men and guns from the enemy's
projectiles; a _scarp wall,_ which sustains the pressure of the earth of
the rampart and parapet, and presents an insurmountable obstacle to an
assault by storm; a wide and deep _ditch_, which prevents the enemy from
approaching near the body of the place; a _counterscarp wall_, which
sustains the earth on the exterior of the ditch; a _covered way_, which
occupies the space between the counterscarp and a mound of earth called
a _glacis_, thrown up a few yards in front of the ditch for the purpose
of covering the scarp of the main work.

The work by which the space fortified is immediately enveloped, is
called the _enceinte_, or _body of the place_. Other works are usually
added to the enceinte to strengthen the weak points of the
fortification, or to lengthen the siege by forcing the enemy to gain
possession of them before he can breach the body of the place: these are
termed _outworks_, when enveloped by the covered way, and _advanced
works_, when placed exterior to the covered way, but in some way
connected with the main work; but if entirely beyond the glacis, and not
within supporting distance of the fortress, they are called _detached
works_.

In a bastioned front the principal outwork is the _demi-lune_, which is
placed in front of the curtain; it serves to cover the main entrance to
the work, and to place the adjacent bastions in strong re-enterings.

The _tenaille_ is a small low work placed in the ditch, to cover the
scarp wall of the curtain and flanks from the fire of the besieger's
batteries erected along the crest of the glacis.

The _places of arms_, are points where troops are assembled in order to
act on the exterior of the work. The _re-entering places of arms_, are
small redans arranged at the points of junction of the covered ways of
the bastion and demi-lune. The _salient places of arms_ are the parts of
the covered way in front of the salients of the bastion and demi-lune.

Small permanent works, termed _redoubts_, are placed within the
demi-lune and re-entering places of arms for strengthening those works.
Works of this character constructed within the bastion are termed
_interior retrenchments;_ when sufficiently elevated to command the
exterior ground, they are called _cavaliers._

_Caponniers_ are works constructed to cover the passage of the ditch
from the tenaille to the gorge of the demi-lune, and also from the
demi-lune to the covered way, by which communication may be maintained
between the enceinte and outworks.

_Posterns_ are underground communications made through the body of the
place or some of the outworks.

_Sortie-passages_ are narrow openings made through the crest of the
glacis, which usually rise in the form of a ramp from the covered way,
by means of which communication may be kept up with the exterior. These
passages are so arranged that they cannot be swept by the fire of the
enemy. The other communications above ground are called _ramps, stairs,_
&c.

_Traverses_ are small works erected on the covered way to intercept the
fire of the besieger's batteries.

_Scarp_ and _counterscarp_ galleries are sometimes constructed for the
defence of the ditch. They are arranged with loop-holes, through which
the troops of the garrison fire on the besiegers when they have entered
the ditch, without being themselves exposed to the batteries of the
enemy.

In sea-coast defences, and sometimes in a land front for the defence of
the ditch, embrasures are made in the scarp wall for the fire of
artillery; the whole being protected from shells by a bomb-proof
covering over head: this arrangement is termed a _casemate_.

Sometimes double ramparts and parapets are formed, so that the interior
one shall fire over the more advanced; the latter in this case is called
_a faussebraie_.

If the inner work be separated from the other it is called a
_retrenchment_[44] and if in addition it has a commanding fire, it is
termed, as was just remarked, a _cavalier_.

[Footnote 44: The term _retrenchment_ implies an interior work, which is
constructed within or in rear of another, for the purpose of
strengthening it; the term _intrenchment_, on the contrary, implies an
independent work, constructed in the open field, without reference to
any other adjoining work.]

The _capital_ of a bastion is a line bisecting its salient angle. All
the works comprehended between the capitals of two adjacent bastions is
termed a _front_: it is taken as the unit in permanent fortification.

Fig. 39 represents the ground plan of a modern bastioned front, of a
regular and simple form, on a horizontal site.

_A, A, A_--Is the enceinte, or body
of the place.
_B_--The bastions.
_C_--The main ditch.
_D_--The covered ways.
_E_--The re-entering places of arms.
_F_--The salient places of arms.
_G_--The demi-lune.
_H_--The demi-lune ditch.
_J_--The demi-lune redoubt.
_L_--The ditch of the demi-lune
redoubt.
_M_--The redoubt of the re-entering
places of arms.
_N_--The ditches of the redoubts.
_O_--The tenaille.
_P_--The double caponier.
_a_--The traverses.
_b_--The sortie-passages.
_c_--Stairs.
_d_--Cut in the demi-lune to flank
the redoubt of the re-entering
place of arms.

Fig. 40 represents a section through the line _mn'_ of the preceding
figure.


_A_--Is the rampart.
_B_--The parapet.
_C_--The ditch.
_D_--The scarp wall.
_E_--The counterscarp wall.
_F_--The glacis.
_G_--The covered way.
_H_--The terre-plain.
_J_--The parade.

Sometimes half embrasures are cut in the earthen parapet of a fort, so
as to sink the gun below the crest, and thus more effectually cover the
men from the enemy's fire.

But guns in embrasure have a far less extended field of fire than when
mounted in barbette; moreover, the embrasures present openings through
which an enemy may penetrate in an assault. Owing to these objections,
they are employed only for the protection of particular points; that is,
where it is important to cover the artillerists from the enemy's fire,
or where the guns are to be used merely to protect a ditch, or to
enfilade a road, &c. The bottom of the embrasure is called the _sole_,
the sides are called _cheeks_, and the mass of earth between two
embrasures, the _merlon_. Embrasures may be made either direct or
oblique, according as the fire is required to be perpendicular or
oblique to the parapet.

A _coverport_ is a small outwork of any convenient form, erected
immediately in front of a gateway, to screen it from the enemy's fire.

A _counterguard_ is a more extensive work, constructed in front of a
part of the fortress itself, or of some other outwork of greater
importance, which it is intended to cover. These are sometimes called
_coverfaces_, from their situation and object; but the former term is
most commonly used.

Sometimes outworks, called _tenaillons_, consisting of one long and one
short face, are placed on each side of the demi-lune of a front of
fortification, for the purpose of prolonging the siege. (Fig. 41.)

Small, or _demi_-tenaillons, are frequently so arranged as to cover only
one-half of the demi-lune, and then a _bonnet_ constructed in front of
the salient of the demi-lune. (Fig.42.) In this case the bonnet is
flanked by the short faces of the demi-tenaillons; these short faces are
themselves flanked by the demi-lune, while the bastions flank the long
faces.

A _horn-work_ consists of a front of fortification, and two wings
resting on the faces of bastions of a front of the fortress. It
sometimes has also a demi-lune or bonnet, as in the case of
demi-tenaillons. (Fig. 43.)

A _crown-work_ consists of two fronts of fortification, and two wings.
(Fig. 44.) It is sometimes made _double_, and even _triple_.

These works are also employed as advanced works, and placed entirely in
front of the glacis. They have generally been added to a fortress for
the purpose of occupying some important piece of ground not included
within the limits of the main work. They may be constructed with covered
ways, and sometimes it may be found advantageous to secure them by
retrenchments.

A _detached work_ may be made in any form deemed best suited to the
site. Being but remotely connected with the fortress, the latter will
exercise but slight influence on the character of its plan or
construction. They are usually of limited extent and slight relief,
partaking much of the nature of field-works.[45]

[Footnote 45: The general principles of permanent fortification may be
best learned from the writings of Cormontaigne, St. Paul de Noizet, and
Laurillard-Fallot. A list of valuable books of reference on the several
branches of military engineering will be given at the close of the next
chapter.]




CHAPTER XIV.

FIELD-ENGINEERING.


_Field-Engineering_ includes the making of military reconnaissances,
temporary fortifications, and military roads; the planning and
construction of military bridges; the attack and defence of military
works;--in fine, all the various duties of engineer troops, either in
the operations of a campaign, or in the dispositions on the
battle-field.

_Military reconnaissance._--By this term is meant an examination of a
portion of the theatre of war, to ascertain its military character and
resources. If the examination be made of a large district of country,
and for an entire campaign, the reconnaissance is _general_; if made for
collecting detailed information respecting a proposed line of march, the
passage of a river, the position of an enemy, &c., it is termed
_special_.

In making a general reconnaissance, great care should be taken to
collect accurate information respecting the general topography of the
country; the character of the mountains, forests, and water-courses; the
nature of the roads, canals, and railways; the quality of the soil, and
the amount of provisions and forage it produces; the population and
character of the cities, towns, and villages, the commercial and
manufacturing resources of every part of the country, and the means of
transportation to be found in each district. The plan of military
operations will be based on the information thus obtained, and any
serious error in the reconnaissance may involve the results of the
campaign, and even the fate of the war.

In a special reconnaissance, not only accurate but minute information
will be required: the character of the roads must be given in detail;
the nature of the water-courses, their depth and velocity; the position
and character of bridges, and fords;--in fine, a full description of all
obstacles to be encountered, and the means that can be made available
for overcoming these obstacles.

A reconnoitring officer may usually derive much valuable information
from the published maps and descriptions of the country to be examined;
additional matters of detail may be obtained from woodsmen, hunters, and
fishermen; and also from the innkeepers and local authorities of the
district. But the officer should always verify this information, so far
as practical, by personal examination. In making a reconnaissance in the
vicinity of an enemy, he must be supported by a strong escort of mounted
troops, and in all his operations the greatest precaution will be
requisite to ensure success.

Some simple instrument, such as a pocket sextant, or compass, will be
sufficient to enable the reconnoitring officer to measure, with
considerable accuracy, the height of mountains, the width of streams,
&c., and an ordinary scale and dividers will enable him to make a
suitable military sketch.

_Temporary Fortification._--It has been stated in the preceding chapter
that temporary fortifications are properly confined to the operations of
a single campaign, and are used to strengthen positions which are to be
occupied only for a short period; and that they are usually made of
earth, thrown up by the troops in a single day. Temporary
fortifications, as a part of field-engineering, may therefore be
regarded rather as an _arm_ than an _art_. The principles of their
construction are derived, of course, from the theory of permanent
fortification, but in applying these principles to practice in the
field, much greater latitude is allowed than in the exact scientific
arrangement of permanent works.

The purpose of field-works (or intrenchments, as they are commonly
called) is to arrest, or at least to impede, the march of the attacking
foe; to shelter the defensive troops from the missive weapons of the
assailants, and to detain them in a position where they will be exposed
to the fire of the defensive force. The numerical and positive strength
of the assailed may be much less than that of the assailant, and yet an
equilibrium exist; the material obstacles compensating for the
difference in numbers. Intrenchments, though inert masses, must
therefore be regarded as most valuable and important accessaries in the
defence of a position.

Intrenchments consist either of _lines_ of works made to cover extended
positions, or of _detached_ works designed simply to defend the ground
they occupy. The former generally present a front against the enemy in
but one direction, while the latter are usually closed on all their
sides.

The following figures have been employed for the plan of simple
intrenchments, viz.: the polygon, redan, lunette, mitre, star-fort, and
bastion.

_Square_ or _polygonal redoubts_ are the most common forms given to
field-works, on account of the ease of their construction. But they have
many defects. There is a sector without fire in front of each salient,
and the ditches are without protection. The latter objection also holds
good against all circular works.

The _redan_ (Fig. 45) is frequently used to cover a point in rear, as a
bridge, a ford, or a defile. When used alone, its gorge should be closed
by palisades. Its ditches are unprotected.

The _lunette_ (Fig. 46) has nearly the same defects as the redan.

The _mitre_, or _priest-cap,_ (Fig. 47,) may be employed with advantage
when a cross-fire is required on the capital of the work. The
_star-fort_ has all the defects, without the merit of simplicity, which
belong to the polygonal redoubt.

The _bastion-fort_ (Fig. 48) more fully satisfies the conditions of a
good defence than any other plan; but it is less simple and easy of
execution. It is usually composed of four or five fronts, but it may be
applied to a polygon of any number of sides.

For the details of the construction of these several works, we must
refer to the special treatises on field-fortification.

Lines of intrenchments may be made either continuous or with intervals.
In adopting either plan, the engineer should avail himself of all the
natural obstacles presented by the position, so as to diminish the labor
of erecting artificial means of defence.

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