Modern artillery has much simplified the construction of siege
batteries. Formerly siege batteries and rampart batteries opposed each
other with direct fire at ranges not too long for the unaided human
eye, and the shells, travelling with low velocity, bit into the
parapets, and, exploding, produced their full effect. Accordingly the
task of the gunners was, by accurate fire, to destroy the parapets and
embrasures, and to dismount the guns. The parapets of siege batteries
were therefore made from 18 to 30 ft. thick, and the construction of
such batteries, with traverses, &c., involved much work. The height of
parapet necessary for proper protection being 7 ft. 6 in. to 8 ft., a
great deal of labour could be saved by sinking the gun-platforms about
4 ft. below the surface level, but of course this was only possible
where rock or water were not near the surface.
The effect of modern projectiles was to reduce the thickness of earth
necessary for parapets. High velocity projectiles are very easily
deflected upwards by even a slight bank of earth. This is especially
the case with sand. Loose earth is better than compacted earth, and
clay offers the least resistance to penetration. These facts were
taken note of in England more than on the Continent in the design of
instructional siege batteries.
The construction of batteries is moreover vastly simplified by the
long ranges at which artillery will fight in future. It will as a rule
be possible to place howitzer batteries in such positions that even
from balloons it will be difficult to locate them; and even direct
fire batteries can easily be screened from view. This renders parapets
unnecessary, and probably no more protection will be used than light
splinter-proof screens to stop shrapnel bullets or fragments of common
shell. Moreover batteries can be constructed at leisure and by
daylight.
The most important point about the modern battery is the gun platform
for the larger natures of guns and howitzers. These require very solid
construction to resist the heavy shock of discharge. Not long ago it
was thought that the defence would have larger ordnance than the
attack, as anything heavier than an 8 in. howitzer required a concrete
bed, which could not be made at short notice. The Japanese, however,
at Port Arthur made concrete platforms for 11 in. howitzers. It may be
remarked that difficulties which loom largely in peace are often
overcome easily enough under the stress of war.
Another gain to the attack is in connexion with magazines. The old
powder magazines were particularly dangerous adjuncts to batteries,
and had to be very carefully bomb-proofed. Such propellants as
cordite, however, are comparatively harmless in the open. They are
very difficult to detonate, and if set on fire do not explode like
gunpowder. It is therefore unnecessary to provide bomb-proof magazines
for them in connexion with the batteries.
In future sieges the question of supply will be more important than it
has ever been. Leaving out of the question the bringing up of supplies
from the base of operations, the task of distribution at the front is
a very large one. The Paris siege manoeuvres of 1894 furnish some
instructive data on this point. The main siege park was at Meaux, 10
m. from the 1st artillery position, and the average distance from the
1st artillery position to the principal fort attacked was 5000 yds.
The front of attack on Fort Vaujours and its collateral batteries
covered 10,000 yds. There were 24 batteries in the 1st artillery
position; say 100 guns, spread over a front of 4000 yds. To connect
Meaux with the front, the French laid some 30 m. of narrow gauge
railway largely along existing roads. The line was single, with
numerous branches and sidings. They ran 11 regular trains to the front
daily and half-a-dozen supplementary. The amount of artillery material
sent up was over 5000 tons, without any projectiles; but it can easily
be imagined that large demands were also made on transport for other
purposes. For instance, one complete bakery train was sent up daily.
The amount of ammunition sent up would be limited only by the power of
transporting it. A siege train of 100 pieces could probably dispose of
from 500 to 1000 tons of ammunition a day, at the maximum rate of
firing.
But the most important question affecting the sieges of the future
(putting aside accidental circumstances) will be the configuration of
the ground. Assuming that local conditions do not specially favour the
artillery of either side, it is highly probable that the artillery
duel will result in a deadlock. If the besiegers' guns do not succeed
in silencing those of the defence from the 1st or distant artillery
position (which, whether they are in cupolas or in concealed
positions, will in any case be an extremely difficult task), it will
be necessary for the infantry to press in; to feel for weak points,
and to fight for those that offer better positions for fire and
observation. In doing this they will have to face the defenders'
infantry, entrenched, backed by their unsilenced guns, and having
secure places of assembly from which to deliver counter-attacks. The
distance to which they can work forward and establish themselves under
these conditions will depend on the ground. It will then be for the
engineers to cross the remaining space by sap. This, under present
conditions, will be a tedious process, and may even take long enough
to cause the failure of the siege.
As to the manner of the sap, it will certainly be "deep," as long as
the defence retains any artillery power. When the 4 ft. 6 in. sap
already described was first introduced, it was known as a "deep sap";
but the sieges of the future will probably necessitate a true deep
sap, that is one in which the whole of the necessary cover is got
below the surface of the earth.
Such a sap may consist of an open trench, about 6 ft. deep, the whole
of the excavated earth being carried away through the trench to the
rear; or a blinded trench, covered in as it progresses by
splinter-proof timbers and earth; or a tunnelled trench, leaving a
foot or so of surface earth undisturbed. In either case nothing should
be visible from the front to attract artillery fire. As the sap is
completed, it will sometimes be necessary to add a slight parapet in
places, to give command over the foreground for the rifles of the
guard of the trenches.
The sap will have to be pushed up quite close to the defenders'
trenches and obstacles. After that further progress must either be
made by mining, or as seems very probable, by getting the better of
the defenders in a contest with shells from short-range mortars.
Just as in the feudal ages a castle was built on some solitary
eminence which lent itself to the defensive methods of the time, so in
the future the detached forts and supporting points in the girdle of
a fortress will be sited where smooth and gentle slopes of ground give
the utmost opportunity to the defenders' fire, and the least chance of
concealment to the enemy. There will be considerable latitude of
choice in the defensive positions; though not, of course, the same
latitude as when the existence of a precipitous hill was the _raison
d'etre_ of the castle. In some places, as at Port Arthur, the whole
country-side may by reason of its steep and broken slopes be
unfavourable to the defence, though even then genius will turn the
difficulties to account. But wherever it is possible the defender will
provide for a space of 1000 yds. or so, swept by fire and illuminated
by searchlights, in front of his lines. That space will have to be
crossed by sap, and it needs little imagination to realize how great
the task will be for the besieger.
There are other modern methods of siege warfare to be noticed, the use
of which is common to besiegers and besieged. Much is expected of
balloons; but the use of these in war is unlikely to correspond to
peace expectations. They must be kept at a considerable distance from
the enemy's guns, a distance which will increase as the means of
range-finding improve; and as the height from which they can observe
usefully is limited, so is the observers' power to search out hidden
objects behind vertical screens. Thus, suppose a captive balloon at a
height of 2000 ft., and distant 4000 yds. from an enemy's howitzer
battery: and suppose the battery placed behind a steep hill-side or a
grove of trees, at such a distance that a shell fired with 30 deg.
elevation can just clear this screen. The line of sight from the
observer to the battery is inclined to the horizontal at {2000/3 x
4000}, that is 1/6, or roughly 10 deg. It is obvious, therefore, that
the observer cannot see the battery.
Balloon observers are expected to assist the batteries by marking the
effects of their fire. For this to be done on any practical scale a
balloon would be required for each battery: that is, for only 100
guns, some 20 or 25 balloons. These would require an equal number of
highly skilled observers (of whom there are not too many in
existence), besides the other balloon personnel and accessories, and
the means of making gas, which is too much to expect, even if an enemy
were obliging enough to give notice of his intentions.
Telephones and all other means of transmitting intelligence rapidly
are now of the utmost importance to both attack and defence. Maps
marked with numbered squares are necessary for directing artillery
fire, especially from cupolas. Organization in every branch will give
better results than ever before, and the question of communication and
transport from the base of supplies right up to the front needs
detailed study, in view of the great weight of ammunition and supplies
that will have to be handled.
The use of light mortars for the trenches, introduced by Coehoorn and
revived with extemporized means at Port Arthur, needs great attention.
It may be prophesied that the issue of important sieges in the future,
when skilfully conducted on both sides with sufficient resources, will
depend mainly on the energy of the defenders in trench work, on mining
and countermining in connexion with the trenches, and on the use of
light mortars made to throw large charges of high explosive for short
distances with great accuracy.
For a brief narrative of the siege of Port Arthur in 1904, one of the
greatest sieges of history, both as regards its epic interest and its
military importance, the reader is referred to the article
RUSSO-JAPANESE WAR.
DEFINITIONS.--The following definitions may be useful, but have no
place in the evolution of the attack, to which this section is mainly
devoted.
_Investment._--This most necessary, almost indispensable operation of
every siege consists in surrounding the fortress about to be besieged,
so as to cut off its communications with the outside world.
_Preliminary investment_ which is carried out by cavalry and light
troops before the arrival of the besieging force, consists in closing
the roads so as to shut out supplies and reinforcements. _Close
investment_ should be of such a character as to prevent any sort of
communication, even by single messengers or spies. The term
"_blockade_" is sometimes loosely used instead of investment.
_Lines of Circumvallation and Contravallation._--These now obsolete
terms were in great use until the 19th century. The _circumvallation_
was a line of parapet which the besieger made outside the investing
position of his own force, to protect it when there was a chance of
attack by a relieving army. The line of _contravallation_ was the line
of parapet and trench sometimes made by the besieger all round the
town he was attacking, to check the sorties of the garrison.
_Observing Force._--When circumstances make the reduction of a
particular fortress in the theatre of operations unnecessary a force
is often detached to "observe" it. The duty of this force will be to
watch the garrison and prevent any hostile action such as raids on the
lines of communications.
_Bombardment._--This operation, common to all ages, consists in a
general (sometimes an indiscriminate) fire against either the whole
target offered by the fortress or a particular section of that target.
In ancient and medieval times the effect of a bombardment--whether of
ordinary missiles, of incendiary projectiles, or of poisonous matters
tending to breed pestilence--upon a population closely crowded within
its walls was very powerful. In the present day little military
importance is attached to bombardment, since under modern conditions
it cannot do much real harm.