PERMANENT FORTIFICATIONS.
_Fortification_ is defined,--the art of disposing the ground in such a
manner as to enable a small number of troops to resist a larger army the
longest time possible. If the work be placed in a position of much
importance, and its materials be of a durable character, it is called
permanent; if otherwise, it receives the appellation of _field_, or
_temporary_. Fieldworks are properly confined to operations of a single
campaign, and are used to strengthen positions which are to be occupied
only for a short period. Generally these works are of earth, thrown up
by the troops in a single day. They are intimately connected with a
system of permanent fortifications, but from the facility of their
construction, no provision need be made for them before the actual
breaking out of war. Indeed, they could not well be built before
hostilities commenced, as their locality in each case must be determined
by the position of the hostile forces.
Having already described the general influence of permanent
fortifications as a means of national defence, we shall here speak
merely of the principles of their construction. It is not proposed to
enter into any technical discussion of matters that especially belong
to the instruction of the engineer, but merely to give the nomenclature
and use of the more important parts of a military work; in a word, such
general information as should belong to officers of every grade and
corps of an army.
The first species of fortification among the ancients was of course very
simple, consisting merely of an earthen mound, or palisades. A wall was
afterwards used, and a ditch was then added to the wall. It was found
that a straight wall could be easily breached by the enemy's
battering-rams; to remedy this evil, towers were built at short
intervals from each other, forming a broken line of salient and
re-entering parts. These towers or salient points gradually assumed a
shape approximating to the modern bastion.
After the invention of gunpowder and the application of cannon to the
attack and defence of places, it became necessary to arrange earthen
ramparts behind the thin walls of the ancient works, for the reception
of the new artillery. Moreover these walls were soon found inadequate to
resist the missiles of the besiegers, and it became necessary to replace
them by parapets of earth. In order to cover the retaining walls of
these parapets from the besieging batteries, it was also found to be
necessary to lower these walls as much as possible, and to raise the
counterscarps. The traces or plans of the works, however, received no
material change till about the close of the fifteenth century.
It is not known who first changed the ancient towers into bastions. Some
attribute it to an Italian, and with considerable show of reason, for a
bastion was built at Turin as early as 1461. Achmet Pacha, it is said,
fortified Otranto in this way, in 1480, but whether the system was
previously known among the Turks cannot be determined. Others attribute
the invention to Ziska, the celebrated leader of the Hussites. It is
most probable that the transition from the tower to the bastion was a
very gradual one, and that the change was perfected in several countries
at about the same time.
Fortifications, like other arts and sciences, greatly flourished in
Italy under the Medicis, and that country furnished Europe with its most
skilful engineers. Catharine of Medicis introduced into France many of
her countrymen, distinguished in this profession; among these may be
named Bellamat, Bephano, Costritio, Relogio, Vorganno, the two Marini,
Campi, and Hieronimo, who built several important places and directed
the sieges of others. These able foreigners were rivalled by some
distinguished French engineers, who laid the foundation of the "_corps
du Genie_" which has since become a school of military instruction for
the world. Among the early French engineers may be distinguished
Lafontaine De Serré, Feuquières, and St. Remy. Pedro Navarro had been
appointed a member of this corps, but his attention was more specially
directed to mining, and we do not learn that he distinguished himself in
the construction of any fortification.
In Germany, in the beginning of the sixteenth century, Albert Durer
distinguished himself as a writer on fortification; his book is
remarkable as containing the germs of many of the improvements which
were made by those who followed him. This is the more to be wondered at
as he was not a professed engineer. After him followed Spekel, a native
of Strasburg, who died in 1589. His writings are valuable as showing the
state of the art at that time, and the changes which he himself
introduced. He was an engineer of much practical knowledge and
experience, having assisted at the sieges of Malta, Golletta, Vienna,
Jula, Nicosia, Famagusta, &c.
The first French engineer who wrote on fortification was Errard de
Bar-le-Duc, who published near the close of the sixteenth century. As an
engineer, he was rivalled by Chatillon, a man of distinguished merit.
Errard fortified Amiens, built a part of the castle of Sedan, and a
portion of the defences of Calais. Under the reign of Louis XIII.,
Desnoyers, Deville, Pagan, and Fabre were greatly distinguished. Deville
published in 1628. He was a man of much learning and experience; but he
is said to have adopted, both in his theory and practice, the principles
of the Italian school, with most of its errors. Pagan began his military
career while young, and became _maréchal de champ_ at the age of 38,
when, having the misfortune to become blind, he was compelled to
relinquish his brilliant hopes. He was the ablest engineer of his age,
and was also greatly distinguished in other branches of science. In his
plans he inclined to the Dutch rather than the Italian school of
fortification. He published in 1645.
At the close of the sixteenth century, the Dutch had been forced to
resort to military defences to protect themselves against the
aggressions of the Spaniards. As the Dutch were inferior in other
military means, fortification became one of the vital resources of the
country. Their works, however, thrown up in much haste, were in many
respects defective, although well adapted to the exigencies of the time.
Freytag, their principal engineer, wrote in 1630. Some of his
improvements were introduced into France by Pagan. He was preceded by
Marolois, (a cotemporary of Pagan,) who published in 1613.
In Germany, Rimpler, a Saxon, wrote on fortification in 1671. He was a
man of great experience, having served at the sieges of Candia,
Phillipsburg, Bonn, Riga, Bremen, Dansburg, Bommeln, &c. He fell at the
siege of Vienna in 1683. His writings are said to contain the groundwork
of Montalembert's system.
In Italy, after the time of Tartaglia, Marchi, Campi, &c., we find no
great improvement in this art. Several Italians, however, distinguished
themselves as engineers under the Spaniards. The fortifications of
Badajos are a good example of the state of the art in Italy and Spain a
that epoch. The citadel of Antwerp, built by two Italian engineers,
Pacciotti and Cerbelloni, in 1568, has become celebrated for the siege
it sustained in 1832.
The age of Louis XIV. effected a great revolution in the art of
fortification, and carried it to such a degree of perfection, that it
has since received but slight improvement. The years 1633 and 1634 are
interesting dates in the history of this art, as having given birth
respectively to Vauban and Coehorn. The former was chief engineer of
France under Louis XIV., and the latter held a corresponding position
under the Dutch republic. Coehorn's ideas upon fortification are
conceived with an especial view to the marshy soil of his own country,
and, although well suited to the object in view, are consequently of
less general application than those of his more distinguished
cotemporary and rival. The best specimens of his mode of construction
that exist at the present day, are the fortresses of Manheim,
Bergen-op-Zoom, Nimiguen, and Breda.
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.]