Elements of Military Art and Science Or, Course Of Instruction In Strategy, Fortification, Tactics Of Battles, &C.; Embracing The Duties Of Staff, Infantry, Cavalry, Artillery, And Engineers; Adapted online

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.

The simplest arrangement for a continuous intrenchment is the
_cremaillière_ or indented line. When applied to an irregular site, or
used to connect together distant and detached works, the indented line
may be regarded as a good disposition. Mitres and redans, connected by
straight curtains, are sometimes employed, as also a combination of
large and small redans, forming alternate salient and re-entering
angles. A continuous line of bastions is preferable to any other
arrangement, when there is plenty of time for their construction.

Lines with intervals are frequently formed of alternate lunettes and
square redoubts. Other detached works may be employed in the same way.
This manner of intrenching a position has several advantages, with
disciplined troops. The first shock of the assailant is sustained by the
detached works, and when he attempts to penetrate in the intervals, his
flanks become exposed to a deadly cross fire. These intervals also allow
the assailed to act on the offensive, by charging the enemy at the
opportune moment. But with raw and militia forces it will be safer to
resort to continuous lines. If cavalry form any part of the defensive
force, it will be absolutely necessary to leave intervals through which
these troops may charge.

A vertical section of all intrenchments is of the same general form; the
dimensions will, of course, vary with the nature of the soil, and the
time and means employed in their construction. The minimum dimensions
that can be used with any considerable advantage are given in Fig. 49.

In laying out field-works advantage should be taken of all available
artificial obstacles, such as hedges, walls, houses, outbuildings, &c. A
thickset hedge may be rendered defensible by throwing up against it a
slight parapet of earth. Stone fences may be employed in the same way.
Walls of masonry may be pierced with loop-holes and arranged for one or
two tiers of fire. The walls of houses are pierced in the same manner,
and a projecting wooden structure, termed a _machicoulis gallery_, is
sometimes made from the floor of the second story, to enable the
assailed to fire down upon their opponents. This arrangement is
frequently employed to advantage in wooden blockhouses against a savage
foe; but it is of little avail when exposed to the fire of artillery.
Some have proposed galleries of this description in permanent works of
masonry, but the project is too obviously absurd to merit discussion.

In addition to the parapet of an intrenchment, a good engineer will
always find time and means for constructing other artificial obstacles,
such as trous-de-loup, abattis, palisades, stockades, fraises,
chevaux-de-frise, crows'-feet, mines, &c.

_Trous-de-loup_ are pits dug in the earth in the form of an inverted
truncated cone, some six feet in diameter, and about the same number of
feet in depth. They are usually placed a few yards in front of the
ditch, and concealed by some slight covering.

_Abattis_ are tops and large limbs of trees arranged along the glacis of
a work; the ends of the branches are lopped off and sharpened.

_Palisades_ are stakes some eight or ten feet long, with one end
fastened in the ground and the other made sharp. They are placed in
juxtaposition and connected together by horizontal riband-pieces. This
arrangement is frequently placed at the foot of the counterscarp. When
the timbers are large and the work is intended as a part of a primary
defence, it is called a _stockade_; when the stakes are placed at the
foot of the scarp, either horizontally or inclined, they receive the
name of _fraises_.

A _cheval-de-frise_ consists of a horizontal piece of timber armed with
wooden or iron lances, which project some eight or ten feet. It is much
employed against cavalry, and on rocky soils serves as a substitute for
palisades.

_Crows'-feet_ are small wooden or iron forms filled with sharp spikes.
They are thrown, with their points upward, on ground which is to be
passed over by cavalry.

_Mines_ are sometimes used in connection with intrenchments, but more
commonly in the attack and defence of permanent works. They will be
noticed further on.

Fieldworks which are to be occupied for a considerable length of time
will usually have their steeper slopes revetted, and be arranged with
scarp and counterscarp, galleries, traverses, blindages, &c. Such works
hold an intermediary rank between temporary and permanent fortification.

As examples of the importance of field fortifications and of the manner
of organizing them, the reader is referred to the celebrated battle of
Fontenoy, in 1745, where the carefully-arranged intrenchments of Marshal