D. Close with barrier forts the lines necessary to an enemy across
mountains or marshes.
E. Make a central place behind a mountain chain as a pivot for the
army watching it.
F. Defend mountain roads by provisional fortifications.
G. Make a large place in each theatre of war which is far from the
principal theatre, and where the enemy might wish to establish
himself.
H. Fortify coasts and harbours.
Objections to these proposals will be readily supplied by the
officials of the national treasury and the commanders-in-chief of the
active armies.
Types of detached forts.
So many types of detached forts have been proposed by competent
authorities, as well as actually constructed in recent years, that it is
impossible here to consider all of them, and a few only will be
reproduced of those which are most representative of modern continental
thought.
Taking first the type of heavily armed fort, which contains guns for
the artillery fight as well as safety armament, we must give
precedence to General Brialmont. The two works here shown are taken
from the _Progres de la defense des etats, &c._, published in 1898.
The pentagonal fort (fig. 47) has two special features. In section 1
is shown a concrete infantry parapet, with a gallery in which the
defenders of the parapet may take shelter from the bombardment
preceding an assault. In section 2 it will be seen that the
counterscarp galleries flanking the ditch are drawn back from the face
of the counterscarp. This is to counteract proposals that have been
made to obscure the view from the flanking galleries, and perhaps
drive the defenders out of them by throwing smoke-producing materials
into the ditch at the moment of an assault. The arrangement may save
the occupants of the galleries from excessive heat and noxious fumes,
but will not of course prevent the smoke from obscuring the view.
The following points may be noticed about this design in comparing it
with earlier types. There is no escarp, the natural slope of the
rampart being carried down to the bottom of the ditch. There is a
counterscarp to the faces, but no covered way. The flanks have no
counterscarp, but a steel fence at the foot of the slope, and the
covered way which is utilized for a wire entanglement which is under
the fire of the parapet. The gorge has a very slight bastioned
indentation, which allows for an efficient flanking of the ditch by a
couple of machine guns placed in a single casemate on either side.
The abolition of the covered way as such is noteworthy. It marks an
essential difference between the fort and the old enceinte profiles;
showing that offensive action is not expected from the garrison of the
fort, and is the duty of the troops of the intermediate lines.
The great central mass of concrete containing all the casemates and
the gun-cupolas, a very popular feature, is omitted in this design,
advantage being taken of the great lateral extent of the fort to
spread the casemates under the faces, flanks and gorge, with a
communication across the centre of the fort. This arrangement gives
more freedom to the disposition of the cupolas. The thickness of the
concrete over the casemate arches is more than 8 ft. Communication
between the faces and the counterscarp galleries is obtained by
posterns under the ditch. The armament, which is all protected by
cupolas, is powerful. It consists of two 150-mm. (6 in.) guns, four
120-mm. (4.7 in.) guns, two 210-mm. (8.4 in.) howitzers, two 210-mm.
(8.4 in.) mortars, four 57-mm. Q.F. guns for close defence. There is
also a shielded electric light projector in the centre.
This fort is a great advance on General Brialmont's designs before
1885. These were marked by great complexity of earth parapets and
various _chicanes_ which would not long survive bombardment. This type
is simple and powerful. It is also very expensive.
The second Brialmont fort (fig. 48) is selected because it shows a
keep or citadel, an inner work designed to hold out after the capture
of the outer parapet. General Brialmont held strongly to the necessity
of keeps for all important works. History of course gives instances of
citadels which have enabled the garrison to recapture the main work
with assistance, or caused a really useful delay in the progress of
the general attack. It affords still more instances in which the keeps
have made no resistance, or none of any value. Some think that the
existence of a keep encourages the defenders of the main work; others
that it encourages the idea of retreat. The British school of thought
is against keeps. In any case they add largely to expense.
In the present design the keep is a mass of concrete, which depends
for the defence of its front ditches on counterscarp galleries in the
main work, the few embrasures for frontal defence being practically
useless. Its main function is to prevent the attackers from
establishing themselves on the gorge, thus leaving the way open for a
reinforcement from outside to enter (assisted by bamboo flying
bridges) through the passages left for the purpose in the outer and
inner gorge parapets.
As regards the main work, the arrangements for defence of the ditch
and the armament are similar to the design last considered. This
parapet has no concrete shelter for the defenders. The casemates are
all collected in the keep and the gorge, with a passage all round
giving access to the parapet and the cupolas.
[Illustration: From Brialmont's _Progres de la defense des etats,
&c._, by permission of Commandant G. Meeus.