D. H. (Dennis Hart) Mahan.

Summary of the course of permanent fortification and of the attack and defence of permanent works, for the use of the cadets of the U.S. Military Academy online

. (page 17 of 29)
Online LibraryD. H. (Dennis Hart) MahanSummary of the course of permanent fortification and of the attack and defence of permanent works, for the use of the cadets of the U.S. Military Academy → online text (page 17 of 29)
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tliis work, the polygonal system, with caponniere defences, of
Montalembert, has been adopted as the basis, with such modi-
fications as the features of the site afforded, t<> withdraw the
principal Lines from the range of the enfilading views from




G19...In tlie organization of works with wet ditches, the Ger-
man engineers adopt the same general disposition of the ele-
ments of a front as they do in dry ditches; occupying the moat
important points of the polygon to be enclosed by independent
Works, and composing the enceinte of fronts of the polygonal
system? taking their exterior sides between the limits of 350
and 050 yards, and sweeping the main ditch, and the positions
for the besieger's breaching batteries around the salients of the
enceinte, by the flanks of a defensive caponniere. The follow-
ing concise description of a front of the teU <l< pont opposite
Germersheim, will give a good idea Of the general defensive
arrangements in such eases.

02O...Plan. The front, X Y, PL 33^ Fig. 1, is a tenailled
line with a slight reentering at the centre of the exterior side.
The salients of the front are occupied by small bastions, with a
scarp gallery on the faces and thinks, and having its gorge
closed by a loop-holed wall, with a defensive, casemated reduit
at its centre.

621. ..The centre of the front is occupied by a capacious case-
mated edifice, which extends from the interior of the gorge of
the independent work, across the main ditch, to within the
enceinte. The circular portion of this edifice, jwithin the inde*
pendent work, has two tiers of covered fire, with an open bat-
tery on top, and serves as the reduit of this work. The central
portion has two tiers of covered fire, and serves as a caponniere
for sweeping the main ditch, etc. Underneath this portion are
arched passages, to communicate by water between the ditch
on each side of the caponniere. The part of the edifice within
the enceinte is a defensive barrack, with three tiers of covered


fire, and an open battery on top, from which the terreplein of
the enceinte curtain, the gorges of the bastions and the glacis
of tfie enceinte can be swept.

622. ..The enceinte curtain is not revetted with masonry.
The exterior slope of its parapet descends to a wide berm .»<v-
eral feet above the water level of the wet ditch, and which, in
many places, is planted with a thorn thickset hedge as an ol>-
Btacle to an assault. The rampart of the curtain is* sustained
within by a high wall, which joins the loop-holed walls of the
bastion gorg< s, and is flanked by the baBtibn reauits.

623.. .The independent work is ip the form of a lunette; its
faces being divided into three parts, each with a greater com-
mand than the oneain its rear. The profile of this work is like
that of the enceinte curtain ; its ditches are dry. their bottoms
being slightly above the water level of the main ditch. The
ditches are flanked by casemated caponnieres which extend
across them to the goTges of the reentering places of arms, for
which works they al>o serve as reduits. They are connected
with the central rednit by loop-holed walls.

oi'4...The covered-ways are without .traverses. A casemated
reduit or traverse separates the reentering place.- bf arms, on
each side, from the coVered-ways bf the enceinte and independ-
ent work, and sweeps them both. These are connected by
loop-holed walls in front, which join those in their rear.

625. ..The counterscarps of the enceinte and independent

work are of earth.

626.. .A passage leads from the interior across the main ditch
on each sid< • ■' tl • central casemated edifice, and extends along
the counterscarp of the enceinte. This passage is a few
above the water level, the two ends being connected by brid<
across that portion of the main ditch where the arched Com-
munication under the main caponnien

\ ept by two small, casemated caponn iiich pro

from the - d. - of the main caponni

7...Iiani].s lead from the . to the inte-

1 98 WOBK at (.1 i:m;

rior of the independent work at its gorge, and to that of the.
reentering places of arm*

628.. .An interior ami exterior system of mines is connected
with the independent work and the r&duita of the reentering

place ft' an.

0:2!'... In the application of this system to wet ditches., the
means of. communication between the enceinte and the various

outworks, .by the passages and small bridges, across the main
ditch and along the sides of the central caponniere, are princi-
pally npticeable, as the other features do not differ in any great
degree from its application to dry ditches. Here, one of the
main objections to wet ditches, the difficulty of keeping open a
communication by means of rafts or boats, for sorties and other
purposes, is obviated by the arrangement of the passage in
question. The bridges, connecting the break in this passage,
may be so arranged as to be readily removed or destroyed
when the besieger has gained such a footing beyond the main
ditch as, by a rapid assault) to endanger the* safety oi' the en-
ceinte. This mode, however, of establishing a foot communi-
cation between the enceinte and the outworks of a front, is not
peculiar to this system ; as like means are used in the bastioned
system, by placing the bottom of the double caponniere slightly
above the water level of the main ditch, connecting the two
parts of this ditch, on each side of the caponniere, by a narrow
ditch, between this and the gorge of the demilune redoubt,
over which a slight temporary bridge is thrown, so long as it
is found necessary to keep open this communication.

630.. .The German engineers apply the preceding dispositions
to every class of detached works, whether within reach of the
artillery of the main work or beyond it. In the former case,
the work is either in the form of a lunette or a redan, accord-
ing to the requirements of the site, the gorge of the work being
secured by a slight, loop-holed wall that can be readily de-
stroyed by the artillery of the place, and thus open its, interior
to view when occupied by the besieger. In the latter, the
plan is that of a polygonal redoubt enclosed on all sides by a


parapet. The ditches in nil such cases are flanked by small
osponnieres, placed at the angles of the work, and arranged

both for musketry and artillery, besides a counterscarp gal-
lery, which serves as the point 6f departure tor the galleries of
the exterior system of mines.

631. ..Remarks. The apparently wide divergence beweCn
the German fort in' ration of the present day and the bastioned
system, which lasl had been adopted as the normal one thrdugh-
out the world until these innovations were practically intro-
duced, has given rise to active discussions among engineers in
Europe, in which, as in all such cases, very ultra ground has
been taken by both parties to the dispute. In each system the
points admitted as GBsential in all fortification of a permanent
character are sought for, viz: lsfy an enceinte secure from es-
calade and thoroughly flanked by artillery and small arms ;
2d, Mich an adaptation of the plan of. the enceinte to the site
as shall secure, as fill as practicable, the principal lines from
enfilading views ; .'Id, outworks of sufficient strength in them-
selves, and of such defensive relations to the enceinte, as to
force th :• to carry them by regular approaches before

being able to assault the enceinte; 4th. interior defensive
works, or keeps within the assailable points of the enceinte,
and in the outworks first Subject to an attack, to give confi-
dence to their garrisons in holding out to the last extremity;
r>tli. the means necessary for an active defence* 6th, the use of
mines as an auxiliary : 7th, the protection of all masonry by
earthen masks from the distant batteries of thi

J. ..The only question then is. by which of these two ■

terns the object in view ' I attained. Tn the solution of

. we are nut at the outset by the ;t b- any

reliable teste as to the real value of t 1 (op-

ted in th< G Noplace fortified by thi.- mode

subjected to . and nothing can. t ;

be with certainty stated a- to the degn e i the pe-

culiar d- lopted may I ted to at

■ some experiments made at "Woolwich, England, some

200 WORK A I ci KM! B8HXDC.

years ago, to test the practicability of breaching detached
scarps, uke those of Cannot, when covered by an earthen mask,
with heavy guns throwing their projectiles, within the usual
range of ricochet fire, over the earthen mask to reach the wall
covered by it; and others made at Bapaune, France, on the
effects of shptondef -. Kiese experiments* to-

isr with Bome facts dmwn from the sieges in Italy and
Spain* during the period between the first French revolution
and the peace of L815, and the more recent attacks on fortifi-
cations during tlie straggle, between Russia and the Allies, go

to .-how thai all structures of masonry, whenever they can he
reached by heavy projectiles within the range of 800 to L,000
yard.-, whether in view or not, may be greatly damaged it* not
entirely ruined; and that troops within defensive casemates
exposed to such a fire, would be soon driven out of them hv
thc embrasure shots, and the cannon destroyed. Thai the
flanking cappnniereja of the enceinte and of the independent.
works in the German .systems are thus exposed and liable to
these objections, does not admit of a question. Like assertions
may he made of the scarps, which are either wholly or partly
detached, and of the traverse walls by which the corridors of
the enceinte are divided tor defence. The defensive harracks
in the gorges of the independent works, and which serve as
their reduits, as well as the loop-holed wall by which the gor-
ges of these works are closed, being thrown back from the
cover of their parapets, are also similarly exposed. The Ger-
man engineers, it is said, have, by the dispositions made in
some of their more recent structures, by abandoning the conn-
tersloping glacis of Carnpt and his detached scarps, employing
in their stead, on fronts of attack, scarps with relieving arches,
and covering, to some extent, their ditch caponniere defei
by earthen masks, shown some distrust of the methods mostly
nsed in their firs! structures, planned upon the views of Mon-
talemhert and Carnot.

633. ..The polygonal trace, which obtains in most of the re-
cent German works, has certain prominent advantages and

WORK ai <. u:\ii k-iium. 'Jul

defects which may be seen bv a slight comparison with the
bastion. m1 system. As the exterior sides are longer/land the
reenterings of the enceinte less deep than in' the bastioned
systems, it billows: l.-t, that the interior space enclosed bv the
eaceinte is greater in the polygonal trace; 2d, that the face- of
the enceinte arc less exposed to ricochet from the greater ob-
tuseness of the salient angles; 3d, that the fire of the faces
have thus a better bearing on the distant defence; 4th, that,
requiring fewer fronts on a given extent of line to be fortified,
there will be fewer flanks and more artillery, therefore) di>-
posable for the faces and curtains; 5th, that, in the asnal
mode of attack, the besiegers will be forced into a greater
development of trenches for the same number of fronts. Such
are the advantages inherent in this trace.

'!.'U...It> defects are; 1st, that the enceinte 1 having no other
flanking defence than the main caponniere, it will be exposed
to an escalade SO SOOD as the tire bf this defence is silenced;
id, that tin- progress of the b . during the last and most

important period of the - but little delayed, owing to

the slighter reenterings formed bv the independent works in
front of the enceinte salients.

...,'IJli" defects in the bastioned trace, and the modes pro-

d by different engineers to remedy them, particularly
tlo ..-'• of Qaxo and Ohoumara, have been sufficiently dwelt
Upon to show that, with the advantages inherent in this 1
of preserving the means of flanking the enceinte ditch to the
last, of throwing the bastion salient- into deep reenteri
giving a belter direction to the enceinte faces for sweeping the

ind in advance of the demilune salient ptible of

iving all the mean- of casemated defences, of a greal
velopment of flank tire, of defensive arrangements of mines, of
ample communications tor an active defence, and an extension
of the exterior side, fortified comrat nsnrate with the impn
late years i:i artillery and -mall arm>.

••"....In t Ich have taken place UDOD

its of these two tra

202 1. 1 KM AX FOKTS.

rival schools, each has seemed disposed to exaggerate the de-
fects and to depreciate the advantages of the system analyzed*
and has conducted his mode of attack accordingly. The true
point, however, as to the inherent merits of the question, does
not lie in a comparison of the means of resistance of a bas-
tioned trace, with defective communications and without case-
mated defences and mines, ami that of the German sv.-tem,
but between the former, with these additions, now regarded
by engineers of every school as indispensable to a vigorous de-
fence against the greatly improved means of attack of the pre-
sent day, and the latter.

637. ..The fragility of masonry, and the case with which it
can be ruined by distant batteries of heavy calibre, particu-
larly when pierced with embrasures and loop-holes, like the
.caseinated caponnieres and defensive barracks of the Ger-
man system, must naturally incline engineers to limit its em-
ployment as much as possible, reserving its use for positions
where it will not be subject to this exposure, or where it can
be so covered with an earthen mask that nothing may be ap-
prehended from the besieger's heavy guns.


638. ..In their detached works, or isolated forts, the German
engineers follow the same defensive measures as in the inde-
pendent Avorks belonging to a continuous enceinte. A strong,
casemated barrack, PI. 33, Fig. 2, the plan of which is either
curvilinear or polygonal, with several tiers of lire, serves as
the reduit or keep of the work, and is placed either within it
or at its gorge, according to the position to be occupied. The


inferior is provided with casemates for guns and mortars,
placed at the salients and along the terreplein — frequently
under traverses, when these are used to cover a face from en-
filading views. The scarp walls are usually built with reliev-
ing arches, defensive scarp galleries, and open corridors be-
hind the ap per part of the Boarp wall, which is also loop-holed.
The ditches are flanked by small capon nie res, placed at the
angles of the work, or along its faces, and by loop-holed coun-
terscarp galleries; and mines for exterior and interior defence
are connected with these galleries and with a ditch which
usually surrounds the keep.

639. ..Tower Fobts. The favor with which the views of
Montalemhert have been received in Germany, lias led to the
adoption of his circular casemated towers, both as isolated
forts and combined in a system of detached Works for covering
a ^pace to their rear for an entrenched camp, as at lints.
These towers, in their interior arrangements, are the same as
the defensive barrack already describe*!, with the exception of
those differences in the details of the construction which the
difference in their plans would call for. They have several
tiers of covered fire for artillery and musketry, and an open
battery on top, the parapet of which is either of earth or of
masonry, according to the dimensions of the tower. In the

towers at Lintz they are surrounded by a ditch, and the whole

of the masonry which would be exposed to the bes bat-

teries is covered by a glacis, leaving only the guns on top to
have direct view- on these batteries, the second tier firing
under an elevation over the crest of the glacis mask. The
ditch toward the interior is crossed by a temporary fixed
a drawbridge leading to the second Btoryfof the tower. The
gun.- of the top battery are placed on a revolving platform,
their carriages being of a peculiar construction, t<. admit of
the axes of the guna remaining paralh not to have their

shot div< Tge from tl bjecl to he reached, aid. tme

tim< . ,py as little spaa . la! rally, a- will j for

the service of the guns. An earthen para the guna


on the side exposed to the besieger's fire, and one of masonry
toward tlif interior. These towers, with'the exception of the
open battery, have the defects of divergent fires, common to
all works with a circular plan; and the open battery is liable
to be rendered useless, or be rained by a well-aimed shot or
two, or a heavy shell felling on its platform. The tower-with-
out earthen masks can only be used with advantage in j
tions where it will not be exposed to being breached from a
distance, and is a rery good auxiliary in sea-coast defence, for
points where the ohject is solely to prevent an enemy's Vi
from making use of a safe anchorage on the coast.


640.. .No state, in the present condition of civilization, can
be regarded as secure from foreign military aggression, the ac-
cessible points of whose frontiers are not occupied by perms*
nent fortifications of such strength as shall prevent an enemy
from obtaining possession of them by a sudden assault, and
thus procuring the means of penetrating into the interior.
Guided by the experience of centuries of wars, and the daily
increasing facilities which the improvement.- in the materiel of
armies and their transportation afford for rapid and powerful
offensive operations, the ruling states of continental Europe
have, within the last quarter of a century, not only made every
effort to place their frontiers in an unassailable condition, but
also their great centres of population and wealth in the in-
terior, beyond the chances of a sudden attack from an enemy


who might force his way through tlic frontier defences, and
march rapidly upon them, thus making these positions the
rallying-pointa whore a defeated army can find a safe resting-
place, until it can be reorganized and sufficiently strengthened
t<> resume the offensive. Such seems to be the result "at which
the generals and statesmen of Europe have arrived, after the
most mature and careful consideration of the important prob*
lcm of national defence, during which the utility of permanent
fortifications was seriously called in question by some who
pointed, in support of their views, to the very inefficient part
the great number of fortified places had played in the wars
Waged by Napoleon, when, hy means of overwhelming num-
bers, he was enabled to disregard such places, the garrisons of
which were too feeble to make any efficient offensive move-
ments, until the defeat of his adversary, in one or more great
pitched battles, necessarily also threw them into his possession.
<•}]. ..In view of the arguments bated on these events, the
opinions of Napoleon himself should carry great weight In
speaking of the bearing of permanent fortifications in a defen-
sive war. he says: "If fortresses can neither secure a victory
nor arrest the progress of a conquering enemy, they can at
leas! retard it. and thus give to the offensive the means
gaining time, a most important advantage in all warfare*."

In like manner, the Axohduke Charles, of Austria, who showed

himself one of the ablest adversaries with whom Napoleon
had to cope, takes the ground: "That a defensive warfare can-
not be systematically and successfully carried on in a country
which is not provided with fortresses that have been planned
and distributed according to strategical requirements." lake
views were held hy the Duke of Wellington, and it is proba-
ble that no great general, from the earliest period of military
op-, ral own to tl tit moment, I

the contrary. Without going further hack than the t>
contests which have taken place in Kurop.- within
years, we gather tin

We find, on t; Sorts of powerful

206 Tin: adaptation of pbbmaitknt forttftcatios

Russian forces paralyzed by the obstinate defence of a few
weak fortresses, and, in some cases, of simple field-works by
the Turks; on the other, the gigantic armaments, by sea and
land, of France and England combined, held at bay in the
East, and in the Black Sea; and. more lately, the career of
of France arrested in the very flush of victory, by the time
which it must necessarily have cost her to break down the
barriers which Austria had placed in her way in the strong-
holds of Northern Italy. The only question, then, on this
Subject that remains for solution by a state is in what way
such a means of security from aggression can be best adapted
tn its own geographical) political and military status.

642.. .In a country like our own, with so vast an extent >■['
sea-coast and inland frontier, and with political and social in-
stitutions which are so antagonistic to every approach to the
maintenance of a large standing army as a measure of national
safety, this question is one of peculiar importance, both from
the open character of this extensive frontier, and from the al*
mosl incredible facility with which, as in the late struggles in
Europe, and in the contests of China and India, considerable
armies, with all their materiel, can be concentrated on distant
points by the aid of steam,

64o...The want of military means of some of our immediate
neighbors, and the daily increasing mutual commercial inter-
ests between us and the greatest naval power of the world,
from whom alone we have any serious danger to apprehend
along our inland frontier, would seem to favor the hope that
the day may never arrive in Which our country will have to
provide against invasion except along the sea-coast; and we
may, therefore, dismiss from our consideration any further
provision against this eventuality than the security of our prin-
cipal harbors, naval stations and commercial marts from a
naval attack, or from one combined with the descent of a land
force, which last, from the great resources of our country in
men and ••means, would hardly attempt to penetrate inland be-
yond one or two marches.


644.. .Tn the organization of the frontier fortifications of a
state, the points to be chiefly regarded are the principal ave-
nues of access to the interior, and the topographical features of
the frontiers, as they lend themselves, more #r less, to
strengthen artificial defences. In conducting an invasion
across ao inland frontier, the march of the enemy must nei
sarilv be along the roads that intersect it, as these afford the
only good avenues for transporting the materiel, etc, of the
army. The joints, therefore, or places in their neighborhood,
where the principal roads or other avenues of communication
erosa the frontier, particularly those which lead to the greal
centres of population and wealth, are the ones which neces*
sarilv require permanent defences. No absolute rule can be
laid down for the distribution or the strength of such works.

rything must depend upon the more or less of facilitv pre*
sented to an enemy for penetrating at one point rather than
another, and of the ulterior advantages which the possession
of one may present to him over another.

6 !•'».. .Rivers and mountain ranges are the natural fortifica-
tions of states, and. where they form the frontiers, they greatly
facilitate the application of artificial defensive means, as they
present but few, and those, in general, important points of ac-
cess. When the points bf communication on a river are forti-
fied, an invading force, however powerful, cannot, without
ross the river before first gaining p n of

them; for, even should a sufficient detachment be left to ob-

e and blockade the fortresses, the main army, in case of
' r any disaster, might be placid in bj extremely criti-
cal position, in its movements to recross the river, with I
garrisons of the fortresses threatening its flanks and rear. In
offensive operations, fortresses upon a river frontier form i
of t! • . an army. If a river in-

• lie frontier, the point where it rr
in its vicinity, should he occupied by a p I work.

Online LibraryD. H. (Dennis Hart) MahanSummary of the course of permanent fortification and of the attack and defence of permanent works, for the use of the cadets of the U.S. Military Academy → online text (page 17 of 29)