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

mine is termed _common_; when this radius is greater than the line of
least resistance, the mine is termed _overcharged_; and when the radius
is less, _undercharged_. A mine of small dimensions, formed by sinking a
shaft in the ground, is termed a _fougasse_. The term _camouflet_ is
applied to a mine used to suffocate the enemy's miner, without producing
an explosion. Small mines made in rock or masonry, merely for the
purpose of excavation, without any considerable external explosion, are
called _blasts_.

From experiments made on common mines, whose line of least resistance
did not exceed fifteen feet, it has been ascertained that the tenacity
of the earth is completely destroyed around the crater to a distance
equal to the crater radius, and that empty galleries would be broken in
at once and a half that distance. It has also been proved by experiment,
that the crater radius in overcharged mines may be increased to six
times the line of least resistance, but not much beyond this; that
within this limit the diameter of the crater increases nearly in the
ratio of the square roots of the charge; and that empty galleries may be
destroyed by overcharged mines at the distance of four times the line of
least resistance.

By means of the deductions of physico-mathematical theory, and the
results of experiments, rules have been determined by which the miner
can calculate, with much accuracy, the charge necessary to produce a
required result in any given soil.

In the earlier stages of the history of this art, mines were only used
to open breaches and demolish masses of masonry; but in later times they
have been employed as important elements in the attack and defence of
places.

An isolated wall, only two or three feet thick, may readily be
demolished by exploding one or two casks of powder placed in contact
with its base. If the wall be five or six feet thick, the charges should
be placed under the foundation. For walls of still greater thickness it
will be best to open a gallery to the centre of the wall, a foot or two
above its base, and place the powder in chambers thus excavated.
Revetment walls may be overturned by placing the charges at the back of
the wall, about one-third or one-quarter of the way up from the base. If
placed too near the base, a breach will be made in the wall without
overturning it.

To demolish a bridge of masonry the powder should be lodged in chambers
excavated in the centre of the piers. When there is not time for
excavating these chambers in the piers, a trench may be cut over the key
of the arch, in which the powder is placed and exploded; or, the casks
of powder may be suspended immediately under the arch, with the same
results. Where a saving of powder is of consequence, small chambers may
be excavated in the haunches of the arch, and the mine carefully
_tamped_ before firing it.

Bridges of wood may be destroyed by suspending casks of powder under the
principal timbers, or attaching them to the supports.

Palisading, gates, doors, &c., may be destroyed in the same way, by
suspending casks or bags of powder against their sides; or still more
effectually, by burying the charges just beneath their base.

To demolish a tower, magazine, or house, of masonry, place charges of
powder under the piers and principal walls of the building. In wooden
structures the powder should be placed under, or attached to the
principal supports. Where time is wanting to effect these arrangements,
a building may be blown down by placing a large mass of powder in the
interior. The powder may be economized, in this case, by putting it in a
strong case, which should be connected with the walls of the building on
all sides by wooden props.

Special treatises on military mining contain full instructions for
regulating the size and position of the charge for the various cases
that may be met with in the practical operations of field-engineering.

As applied to the attack and defence of a fortified place, mines are
divided into two general classes - _offensive_ and _defensive_ mines. The
former are employed by the besiegers to overthrow the scarps and
counterscarps of the place, to demolish barriers, palisades, walls, and
other temporary means of defence, and to destroy the mines of the
besieged. The latter are employed by the opposite party to blow up the
besiegers' works of attack, and to defend the passage of ditches against
an assault. Small mines called _fougasses_ may be employed for the last
named object. The _shell-fougasse_ is composed of a wooden box filled
with one or more tiers of shells, and buried just below the surface of
the earth. Sometimes a quantity of powder is placed under the shells, so
as to project them into the air previous to their explosion. The _stone
fougasse_ is formed by making a funnel-shaped excavation, some five or
six feet deep, and placing at the bottom a charge of powder enclosed in
a box, and covered with a strong wooden shield; several cubic yards of
pebbles, broken stone, or brickbats, are placed against the shield, and
earth well rammed round, to prevent the explosion from taking place in
the wrong direction. These mines are fired by means of powder hose, or
by wires connected with a galvanic battery.

The defensive mines employed to blow up the besiegers' works, are
generally common mines with the lines of least resistance seldom greater
than fifteen feet. All the main galleries and principal branches of
mines for a permanent fortification are constructed at the same time
with the other portions of the work, leaving only the secondary
branches, chambers, &c., to be made during the siege. For the general
arrangement of these galleries, and the precautions necessary for their
protection from the operations of the besiegers, reference must be made
to treatises specially devoted to the discussion of this subject.

Mines can seldom be employed with advantage in works of slight relief,
and liable to an assault. But if judiciously arranged in the plan of
their construction, and well managed during the operations of the siege,
they contribute very materially to the length of the defence.

_Attack and defence_. - This subject admits of two natural divisions:
1st, of intrenchments, and 2d, of permanent works.

I. Intrenchments maybe attacked either by _surprise_, or by _open
force_. In either case the operations should be based on exact
information of the strength of the works and the number and character of
the garrison - information that can be obtained from spies, deserters,
and prisoners, and confirmed by examinations or reconnaissances made by
officers of engineers. By these means a pretty accurate knowledge may be
obtained of the natural features of the ground exterior to the works;
their weak and strong points; and their interior arrangements for
defence.

In an attack by surprise, the troops should consist of a storming party
and a reserve of picked men. The attacking column is preceded by a
company of sappers armed with axes, shovels, picks, crowbars, &c.; bags
of powder are also used for blowing down gates, palisades, &c. All the
operations must be carried on with the utmost dispatch. The time most
favorable for a surprise is an hour or two before day, as at this moment
the sentinels are generally less vigilant, and the garrison in a
profound sleep; moreover, the subsequent operations, after the first
surprise, will be facilitated by the approach of day. Under certain
circumstances, it may be advisable to make false attacks at the same
time with the true one, in order to distract the attention of the
garrison from the true point of danger. But false attacks have, in
general, the objection of dividing the forces of the assailants as well
as of the assailed. In all attacks by surprise, secrecy is the soul of
the enterprise.

In an open assault, if artillery be employed, the troops should be drawn
up in a sheltered position, until the fire of the works is silenced, and
breaches effected in the parapet. But if the bayonet alone be resorted
to, the troops are immediately brought forward at the beginning of the
assault. The attack is begun by a storming party of picked men: they are
preceded, as before, by a body of sappers, provided with necessary means
for removing obstacles, and followed by a second detachment of
engineers, who will widen the passages, and render them more accessible
to the main body of troops who now advance to the assistance of the
storming party. If the assailants should be arrested at the counterscarp
by obstacles which must be removed before any farther progress can be
made, the infantry troops of the detachment display and open a fire upon
the assailed, in order to divert their fire from the sappers. A few
pieces of light artillery, on the flanks of the column, may sometimes be
employed for this purpose with great advantage.

The storming party should always be provided with scaling-ladders,
planks, fascines, &c., for crossing the ditch, and mounting the scarp.
If the counterscarp be revetted with masonry, the troops must either
descend by ladders, or fill up the ditch with fascines, bales of straw,
bundles of wool, &c.: if not revetted, a passage for the troops into the
ditch will soon be formed by the shovels of the sappers. When the ditch
is gained, shelter is sought in a dead angle till the means are prepared
for mounting the scarp, and storming the work. If the scarp be of earth
only, the sappers will soon prepare a passage for the escalade; but if
revetted with masonry, the walls must be breached with hollow shot, or
scaled by means of ladders.

In the defence, the strictest vigilance should be at all times exerted
to guard against a surprise: sentinels are posted on all the most
commanding points of the work; all the avenues of approach are most
thoroughly guarded; and patroles are constantly scouring the ground in
all directions. At night all these precautions are redoubled. Light and
fire-balls are thrown out in front of the work to light up the ground,
and discover the movements and approach of the enemy. Each man should
have his particular post assigned to him, and be thoroughly instructed
in the duties he will have to perform. All auxiliary arrangements, such
as palisades, abattis, &c., should be defended with the utmost
obstinacy; the longer the enemy is held in check by these obstacles, the
longer will he be exposed to the grape and musketry of the main work.
When he assaults the parapet, he will be opposed by the bayonet in front
and a well-aimed fire in flank. While in the ditch, or as he mounts the
scarp, hollow projectiles, incendiary preparations, stones, logs, &c.,
will be rolled down upon his head. But when the assaulting column has
gained the top of the scarp, the bayonet forms the most effective means
of resistance.

The measures resorted to in the attack and defence of the larger class
of field-works, will necessarily partake much of the nature of the
operations employed in the attack and defence of permanent
fortifications.

II. The attack and defence of a fortress may be carried on either by a
regular siege, or by irregular operations and an assault. The latter
plan has sometimes been adopted when the works of the place were weak
and improperly defended; where the time and means were wanting for
conducting a regular siege; or where the assailants were ignorant of the
means proper to be resorted to for the reduction of the fortress. Such
operations, however, are usually attended by an immense sacrifice of
human life, and the general who neglects to employ all the resources of
the engineer's art in carrying on a siege, is justly chargeable with the
lives of his men. In the siege of Cambrai, Louis XIV., on the
solicitation of Du Metz, but contrary to the advice of Vauban, ordered
the demi-lune to be taken by assault, instead of waiting for the result
of a regular siege. The assault was made, but it was unsuccessful, and
the French sustained great losses. The king now directed Vauban to take
the demi-lune by regular approaches, which was done in a very short
time, and with a loss of _only five men!_ Again, at the siege of Ypres,
the generals advised an assault before the breaches were ready. "You
will gain a day by the assault," said Vauban, "but you will lose a
thousand men." The king directed the regular works to be continued, and
the next day the place was taken with but little loss to the besiegers.

But a work may be of such a character as to render it unnecessary to
resort to all the works of attack which would be required for the
reduction of a regular bastioned fort, on a horizontal site. For
example: the nature of the ground may be such as to enable the troops to
approach to the foot of the glacis, without erecting any works whatever;
of course, all the works up to the third parallel may in this case be
dispensed with without any violation of the rules of a siege. Again, the
point of attack may be such that the other parts of the place will not
flank the works of approach; here a single line of _boyaux_ and short
parallels may be all-sufficient.

But for the purpose of discussion, we will here suppose the place
besieged to be a regular bastioned work on a horizontal site, (Fig.
54.)

The operations of the siege may be divided into three distinct periods.

1st. The preliminary operations of the attack and defence previous to
the opening of the trenches.

2d. The operations of the two parties from the opening of the trenches
to the establishment of the third parallel.

3d. From the completion of the third parallel to the reduction of the
place.

_First period._ The object of the _investment of the place_ is to cut
off all communication between the work and the exterior, thus preventing
it from receiving succors, provisions, and military munitions, and also
to facilitate a close reconnoissance of the place by the engineers, who
should always accompany the investing corps, and pursue their labors
under its protection. This corps should be composed chiefly of light
troops - cavalry, light infantry, horse artillery, "brigades of engineers
and mounted sappers," - who march in advance of the besieging army, and,
by a sudden movement, surround the work, seize upon all the avenues of
approach, and carry off every thing without the work that can be of
service either to the garrison or to the besiegers. To effect this
object, the enterprise must be conducted with secrecy and dispatch.

The investing corps is now distributed around the work in the most
favorable positions for cutting off all access to it, and also to
prevent any communication with the exterior by detachments from the
garrison, and even single individuals are sent out to give intelligence
to a succoring army or to reconnoitre the operations of the besieging
corps. These posts and sentinels, called the _daily cordon_, are placed
some mile or mile and a half from the work, and beyond the reach of the
guns. But in the night-time these posts are insufficient to accomplish
their object, and consequently as soon as it is dark the troops move up
as close to the work as possible without being exposed to the fire of
musketry. This arrangement constitutes the _nightly cordon_.

By the time the main army arrives the reconnoissance will be
sufficiently complete to enable the chief engineer to lay before the
general the outline of his plan of attack, so as to establish the
position of his depots and camp. These will be placed some two miles
from the work, according to the nature of the ground. As they occupy a
considerable extent of ground around the work, it will generally be
necessary to form intrenchments strong enough to prevent succors of
troops, provisions, &c., from being thrown into the place, and also to
restrain the excursions of the garrison. The works thrown up between the
camp and besieged place are termed the _line of countervallation_, and
those on the exterior side of the camp form the _line of
circumvallation_. These lines are generally about six hundred yards
apart. It is not unusual in modern warfare to dispense with lines of
circumvallation, (except a few detached works for covering the parks of
the engineers and artillery,) and to hold the succoring army in check by
means of an opposing force, called the _army of observation_.

The measures of defence resorted to by the garrison will, of course, be
subordinate, in some degree, to those of attack. As soon as any danger
of an investment is apprehended, the commanding general should collect
into the place all the necessary provisions, forage, military munitions,
&c., to be found in the surrounding country; all useless persons should
be expelled from the garrison; a supply of timber for the works of the
engineers and artillery, fascines, gabions, palisades, &c., prepared;
all ground within cannon range around the work levelled; hedges and
trees cut down; holes filled up; temporary buildings demolished or
burnt; and all obstacles capable of covering an enemy and interrupting
the fire of the work, removed.

During this period the engineer troops and working parties detached from
the other arms will be most actively employed. As soon as the investing
corps makes its appearance, bodies of light troops are thrown out to cut
off reconnoitring parties, and, if possible, to draw the enemy into
ambush. To facilitate these exterior operations, and to prevent a
surprise, several guns of long range are placed on the salients of the
bastions and demi-lunes, and others, loaded with grape, in the
embrasures of the flanks, so as to sweep the ditches. About one-third of
the garrison may be employed in exterior operations, and the other
two-thirds in arranging the means of defence in the interior.

_Second period._ - As soon as the engineers have completed their
reconnaissances and determined on the front of attack, and all the other
preparations are made, the general will direct the opening of the
trenches. The ground being previously marked out, battalions of light
troops, termed _guards of the trenches_, as soon as it is dark, are
placed about thirty yards in front of the first parallel, (A. Fig. 54,)
with smaller sections, and sentinels about the same distance further in
advance. These guards lie down, or otherwise conceal themselves from the
fire of the work. The engineer troops and detachments of workmen being
first marched to the dépôts and supplied with all the necessary tools
for carrying on the work, now commence their labors under the protection
of these guards. By daybreak the construction of the first parallel, and
the trenches connecting it with the dépôts, will be sufficiently
advanced to cover the men from the fire of the place; the guards will
therefore be withdrawn, and the workmen continue their labors during the
day to give the trenches the proper size and form.

The _parallels_ are the long lines of trench which envelop the besieged
work, and serve both as covered ways for the circulation of the
besiegers, and as means of defence against sorties from the garrison;
they are therefore arranged with banquettes for musketry fire. The
boyaux are trenches run in a zigzag direction along the capitals of the
front of attack, and are intended exclusively for the circulation of the
troops; they have no banquettes. The first parallel is about six hundred
yards from the place, and consequently beyond the reach of grape. It is
constructed by the _simple sap_. After the first night, the guards,
instead of advancing in front of the work, are placed in the trenches.

The second parallel (B) is made some three hundred or three hundred and
fifty yards from the place, and being much exposed to grape, the
_flying-sap_ is employed in its construction. Batteries (H) are
established between the first and second parallels to silence the fire
of the demi-lunes of the collateral bastions, and others (I) near the
second parallel, to enfilade the faces of the front of attack. These are
armed in part with mortars and in part with heavy siege-pieces.

The works are now gradually pushed forward to the third parallel, (C),
which is constructed about sixty yards from the salients of the place.
As the operations of the besiegers are here greatly exposed to musketry
fire, the trenches are constructed by the _full-sap_. The third
parallel, having to contain the guards of the trenches, and being of
less development than the two preceding, is made much wider. The second
parallel now contains the reserve, and the first parallel becomes the
dépôt of materials. _Demi-parallels_ (G) are frequently established
between the second and third, to be occupied by detachments of guards.

The operations of defence during this period are so directed as to
harass the workmen in the trenches and retard the advance of the works
of attack. Garrison pieces of long range and large howitzers are brought
forward on the salients of the bastions and demi-lunes of attack, so as
to fire in ricochet along the capitals on which the boyaux must be
pushed: light and fire-balls are thrown out as soon as it becomes dark,
to light up the ground occupied by the besiegers, thus exposing them to
the fire of the work and to the attacks of the sortie parties. These
parties are composed of light troops who charge the guards and compel
the workmen to abandon their sapping tools and stand upon the defence.
They are most effective when the besiegers commence the second parallel,
as the guards in the first parallel are not so immediately at hand to
protect the workmen. When the sortie detachment has driven these workmen
from the trenches, instead of pursuing them into the first parallel, it
will display itself in battle order to cover the engineer troops, (who
should always accompany the detachment in this enterprise,) while they
fill up the trenches and destroy the implements of the besiegers. When
the guards of the trenches appear in force, the detachment will retire
in such a way, if possible, as to draw the enemy within range of the
grape and musketry of the collateral works. These sorties, if
successful, may be frequently repeated, for they tend very much to
prolong the siege. The best time for making them is an hour or two
before day, when the workmen and guards are fatigued with the labors of
the night. While the besiegers are establishing their enfilading
batteries, a strong fire of solid shot and shells will be concentrated
on the points selected for their construction. The garrison will also
labor during this period to put the work into a complete state of
defence: constructing all necessary palisadings, traverses, blindages,
barriers; and strengthening, if necessary, the covering of the
magazines.

_Third period._ - After the completion of the third parallel, the
crowning of the covered way may be effected by storm, by regular
approaches, or (if the work is secured by defensive mines) by a
subterranean warfare.

In the first case stone mortar-batteries are established in front of the
third parallel, which, on a given signal, will open their fire in
concert with all the enfilading and mortar batteries. When this fire has
produced its effect in clearing the outworks, picked troops will sally
forth and carry the covered way with the bayonet, sheltering themselves
behind the traverses until the sappers throw up a trench some four or
five yards from the crest of the glacis, high enough to protect the
troops from the fire of the besieged. It may afterwards be connected
with the third parallel by boyaux.

When the covered way is to be crowned by regular approaches, a _double
sap_ is pushed forward from the third parallel to within thirty yards of
the salient of the covered way; the trench is then extended some fifteen
or twenty yards to the right or left, and the earth thrown up high
enough to enable the besiegers to obtain a plunging fire into the
covered way, and thus prevent the enemy from occupying it. This mound of
earth is termed a _trench cavalier_, (O). Boyaux are now pushed forward
to the crowning of the covered way and the establishing of breach
batteries, (J). Descents are then constructed into the ditches, and as
soon as these batteries have made a breach into the walls of the
bastions and outworks, the boyaux are pushed across the ditches and
lodgments effected in the breaches. The demi-lune is first carried; next
the demi-lune redoubt and bastion; and lastly, the interior
retrenchments and citadel. In some cases the breaches are carried by
assault, but the same objection is applicable here as in the storming of
the covered way; _time is gained, but at an immense expense of human