It has been noted already that mining is one of the most ancient
resources of siege warfare. The use of gunpowder in mining operations
dates from the end of the 15th century. When Shakespeare makes Fluellen
say, at Henry V.'s siege of Harfleur, "th'athversary is digt himself
four yards under the countermines; I think 'a will plow up all, if there
is not better directions," he is anticipating the development of
siegecraft by nearly 100 years. Pedro di Navarro, a Spanish officer, is
credited with the first practical use of explosive mines. He employed
them with great success at the siege of Naples in 1503; and afterwards,
when rebuilding the Castello Nuovo after the siege, was probably the
first to make permanent provision for their use in countermines.
Countermining had been a measure of defence against the earlier methods
of attack-mining; the object being to break into the besiegers'
galleries and fight hand to hand for the possession of them. When the
explosive mine was introduced, it became the object of the defenders to
establish their countermines near the besiegers' galleries and destroy
them by the effect of the explosion. In the 400 years or so that have
passed this branch of warfare has changed less than any other. Methods
of mining have not advanced much, and the increased power of high
explosives as compared with gunpowder has its least advantage in moving
masses of earth.
When a besieger has arrived by means of trenches within a certain
distance of the enemy's works without having subdued their fire, he may
find that the advance by sap becomes too slow and too dangerous. He can
then advance underground by means of mine galleries, and by exploding
large charges at the heads of these galleries can make a series of
craters. These craters are then occupied by infantry, and are connected
with each other and with the parallel in rear by trenches, thus forming
a new parallel. If not interfered with by the defenders the besieger can
advance in this way until he reaches the counterscarp. His mines will
now be turned to a new purpose, viz. to breach the counterscarp and
afterwards the escarp. This is done by placing suitable charges at
intervals behind the scarps at such a height above the foundations that
the pressure of the earth above the mine will more than counterbalance
the resistance of the masonry.
Mines and countermines.
But if the defenders are active, they will countermine. There is as a
general rule this broad difference between the mines of the defence and
those of the attack, that the defenders do not wish the surface of the
ground broken, lest increased opportunities of getting cover should be
offered to the besiegers. The object of the defence, therefore, is to
destroy the besiegers' galleries without forming craters, and for this
purpose they generally endeavour to get underneath the attack galleries.
The defenders may, however, wish, if the opportunity is allowed them, to
explode mines under the attack parallels, in which case there is of
course no objection to disturbing the surface.
"At the commencement of the subterranean war the main object of the
defence is to force the besieger to take to mining operations as early
as possible, as it is a tedious operation and will prolong the siege.
Every endeavour must be made to push forward countermines so as to
meet and check the attack. On the approach of the opponents to each
other careful listening for the enemy must be resorted to. To this end
it is necessary at _irregular_ intervals to suspend all work for some
minutes at a time, closing doors of communication and employing
experienced listeners at the heads of the countermines. This matter is
a most important one, as a premature explosion of the defender's mines
is a double loss to the defender, a loss of a mine and an advantage to
the enemy in more than one way. As soon as the overcharged mines of
the besieger have been fired, a heavy fire should be brought to bear
on the craters, and if possible sorties should be made to prevent the
enemy occupying them. At the same time every effort should be made
underground to surround with galleries, and as it were isolate, the
craters so as to prevent the besieger making a new advance from them.
The efforts of the attack at this stage will probably be directed to
the formation of what are called "Boule shafts" (i.e. shafts partially
lined in which charges are hastily fired with little or no tamping),
and to meet these in time the defender may resort to the use of boring
tools, and so place charges somewhere in advance of the heads of the
countermines. His great object must be to prevent as long as possible
the besieger from getting underground again; and these occasions, when
the power of resistance is temporarily equal to, if not greater than,
that of the attack, should be made the most of by the defence."
(Lewis, _Text-book on Fortification, &c._, 1893.)
The defence has the advantage, in the case of fortresses, of being able
to establish beforehand a system of countermine galleries in masonry.
Many systems have been worked out for this purpose. A good typical
arrangement is that of General Marescot, published in 1799, shown in
fig. 72.
[Illustration: From _Textbook of Fortification_, by permission of the
Controller H.M. Stationery Office.