Chapter XI: Part 11

Fig. 50 is Fort Lyngby at Copenhagen. The new Copenhagen defences are
very interesting, giving evidence of clear and original thought, and
effectiveness combined with economy. There is one special feature
worth noting about the outer ring of forts, of which Lyngby is one.
These works are intended for the artillery fight only, their main
armament being four 6-in. guns (in pairs) and three 6-in. howitzers,
all in cupolas. The armament for immediate defence is trifling,
consisting of only two 57-mm. guns and a machine-gun. There is no
provision for infantry defence. The ditch has no escarp or
counterscarp, and is flanked by counterscarp galleries at the salient.

It is usual in the case of works so slightly organized for their own
defence, and intended only for the long-range artillery fight, to
withdraw them somewhat from the front line. The Danish engineers,
however, have not hesitated to put these works in the very front line,
some 2000 metres in front of the permanent intermediate batteries. The
object of this is to force the enemy to establish his heavy artillery
at such long ranges that it will be able to afford little assistance
to the trench attack of the infantry. The intermediate batteries,
being withdrawn, are comparatively safe. They therefore do not require
expensive protection, and can reserve their strength to resist the
advance of the attack. The success of this arrangement will depend on
the fighting strength of the cupolas under war conditions; and what
that may be, war alone can tell us.

In the details of these works, besides the bold cutting down of
defensive precautions, we may note the skilful and economical use of
layers of large stones over the casemates to diminish the thickness of
concrete required. The roofs of the casemates are stiffened underneath
with steel rails, and steel lathing is used to prevent lumps of
concrete from falling on the occupants. The living casemates look out
on the gorge, getting plenty of light and air, while the magazines are
under the cupolas.

The forts above described are all armed with a view to their taking an
important part in the distant artillery fight. The next type to be
considered (fig. 51) is selected mainly because it is a good example
of the use of concealed flanking batteries, known on the continent as
_batteries traditores_, which seem to be growing in popularity.

This design by Colonel Voorduin of the Dutch engineers has a medium
armament, which is not intended for the artillery duel, but to command
the immediate front of the neighbouring forts and the intervals. The
fort is long and narrow, with small casemate accommodation. It
contains eight 4.7-in. guns. Two of these are in a cupola concealed
from view, though not protected, by a bank of earth in front. The
other six are in an armoured battery behind the cupola. It may be
remarked that as the cupola gets no real protection from the covering
mass of earth, it would be better to be able to utilize the fire of
its guns to the front. The _batterie traditore_, if properly protected
overhead, would be very difficult to silence, and its flanking fire
would probably be available up to the last moment. There is very much
to be said both for and against the policy of so emplacing the guns.
The immediate defence of the work, with the aid of a broad wet ditch,
is easy; but the great mass of concrete, which is intended to form an
indestructible platform and breastwork for the infantry, would seem to
be a needless expense.

FIG. 50.--Fort Lyngby, Copenhagen.]

FIG. 51.]

Fig. 52, designed by the Austrian lieutenant field-marshal Moritz
Ritter von Brunner (1839-1904), is selected as a type of the
intermediate fort which is intended only to be a strong point in the
infantry line of defence between the main forts. It has a protected
armament, but this, which consists only of four small Q.F. guns in
cupolas, is for its own defence, and not to take part in the artillery
duel. There is also a movable armament of four light Q.F. guns on
wheels, for which a shelter is provided between the two observatory
cupolas. The garrison would be a half company of infantry, for whom
casemates are provided in the gorge. The gorge ditch is flanked by a
caponier, but there is no flank defence for the front ditch. This is
defended by a glacis parapet. At the bottom of the ditch is a wire
entanglement and the glacis slope is planted with thorns. The
thickness of concrete on the casemates is 2 metres (6 ft. 7 in.). This
is a strong and simple form of infantry work, but considering its role
it appears to be needlessly expensive.

Fig. 53 is an Italian type of barrier fort in mountainous country. A
powerful battery of eight medium guns protected by a Gruson shield
commands the approach. The fort with its dwelling casemates is
surrounded by a deep ditch flanked by counterscarp galleries. There
are certain apparent weaknesses in the type, but the difficulties of
the attack in such country and its limitations must be borne in mind.

_Modern Details of Protection and Obstacle._--After considering the above types of fort, it will be of use to note some of the details in which modern construction has been modified to provide against the increasing power of artillery.

FIG. 52.]

Bomb-proof protection.

The penetration of projectiles varies according to the nature of the soil--the lighter the better for protection. Sand offers the greatest resistance to penetration, clay the least. Since, however, the penetration of heavy shells fired from long ranges with high elevation may be 20 ft. or more in ordinary soil, we can no longer look to earth alone as a source of protection against bombardment. Again a moderate quantity of earth over a casemate increases the explosive effect of a shell by "tamping" it, that is by preventing the force of the explosion from being wasted in the open air. We find therefore that in most modern designs the tops of casemates are left uncovered, or with only a few inches of earth over them, in which grass may be grown for concealment.

For the materials of casemates and revetment walls exposed to fire, concrete (q.v.) has entirely replaced masonry and brickwork, not because of its convenience in construction, but because it offers the best resistance. The exact composition of the concrete is a matter that demands great care and knowledge. It should be, like an armour plate, hard on the surface and tough within. The great thickness of 10 ft. of concrete for casemate arches, very generally prescribed on the continent in important positions, is meant to meet the danger of several successive shells striking the same spot. To stop a single shell of any siege calibre in use at present, 5 ft. of good concrete would be enough. A good deal is expected from the use of "reinforced concrete" (that is concrete strengthened by steel) both for revetment walls and casemates.

Parapets.

Parapets are frequently made continuous or glacis-wise, that is the superior slope is prolonged to the bottom of the ditch so that the whole rampart can be swept by the fire of the defenders from the crest, and there is no dead ground in front of it. It is also common to build the crest of the parapet in solid concrete, with sometimes a concrete banquette, so that bombardment shall not destroy the line the defenders have to man in repelling an assault. This concrete parapet may be further reinforced by hinged steel bullet-proof plates, to give head cover; which when not in use hang down behind the crest.

FIG. 53.]

Obstacles.

The escarp is falling into disfavour, on account of the great expense of a revetment that can withstand breaching fire. A counterscarp of very solid construction is generally used. It is low and gives cover to a wire entanglement in the ditch. This may be supplemented by a steel unclimbable fence, and by entanglements or thorn plantations on the covered way and the lower slopes of the parapet. Entanglements are attached to steel posts bedded in concrete. The upper parts of revetments and the foundations of walls are protected against the action of shells, that falling steeply might act as mines to overturn them, by thick aprons of large stones. Fig. 54 shows most of these dispositions.

Search-lights.

Electric search-lights are now used in all important works and batteries. They are usually placed in disappearing cupolas. They are of great value for discovering working parties at night, and lighting up the foreground during an attack; and since only the projector need be exposed, they are not very vulnerable. Their value, however, must not be over-estimated. The most powerful search-light can in no way compare with daylight as an illuminant, and, like all other mechanical contrivances, they have certain marked drawbacks in war. They may give rise to a false confidence; an important light may fail at a critical moment; and in foggy weather they are useless.

Armour.

The use of armour (see also ARMOUR-PLATES) for coast batteries followed closely upon its employment for ships, for those were the days of short ranges and close fighting, and it seemed natural not to leave the battery in a position of inferiority to the ship in the matter of protection. In England the coast battery for a generation after the Crimean War was a combination of masonry and iron; and in 1860 Brialmont employed armoured turrets at Antwerp in the forts which commanded the Scheldt. For land defence purposes, however, engineers were very slow to adopt armour. Apart from all questions of difficulty of manufacture, expense, &c., the idea was that sea and land fronts were radically different. It was pointed out that a ship gun, fired from an unsteady platform, had not enough accuracy to strike repeated blows on the same spot; so that a shield which was strong enough to resist a single shot would give complete protection. A battery on a land front, on the other hand, was exposed to an accurate fire from guns which could strike successive blows on the same spot, and break down the resistance of the strongest shield. But in time continental opinion gradually began to turn in favour of iron protection. Practical types of disappearing and revolving cupolas were produced, and many engineers were influenced in their favour by the effect of the big high-explosive shell. Eventually it was argued that, after all, the object of fortification is not to obtain a resisting power without limit, but to put the men and guns of a work in an advantageous position to defend themselves as long as possible against a superior force; and that from this point of view armour cannot but add strength to defensive works.

FIG. 54.]

The question has of course long passed beyond the stage of theory. Practically every European state uses iron or steel casemates and cupolas. German, Danish, Italian and other types of forts so armed have been shown. Recent French types have not been published, but it is known that cupolas are employed; and Velichko, the Russian authority, long an uncompromising opponent of armour, in the end changed his views. These countries have had to proceed gradually, by improving existing fortresses, and with such resources as could be spared from the needs of the active armies. Among the smaller states Rumania and Belgium have entered most freely into the new way. In England, which is less directly interested, opinion has been led by Sir George Clarke, since the publication in 1890 of his well-known book on fortification. Having witnessed officially the experiments at Bucharest in 1885 with a St Chamond turret and a Gruson cupola, he expressed himself very strongly against the whole system. Besides pointing out very clearly the theoretical objections to it, and the weak points of the constructions under experiment, he added: "The cost of the French turret was about L10,000 exclusive of its armament, and for this sum about six movable overbank guns of greater power could be provided." In view of the weight that belongs of right to his criticisms it is as well to point out that while this remark is quite true, yet the six guns would require also six gun detachments, with arrangements for supply, &c.; a consideration which alters the working of this apparently elementary sum. The whole object of protection is to enable a few men and guns successfully to oppose a larger number.

At the time when Sir George Clarke's first edition came out, such
extravagances were before the public as Mougin's fort; "a mastless
turret ship," as he called it, "buried up to the deck-level in the
ground and manned by mechanics." Such ideas tended to throw discredit
on the more reasonable use of armour, but whether the system be right
or wrong, it exists now and has to be taken account of. Nowhere has it
been applied more boldly than in Rumania. The defences of Bucharest
(designed by Brialmont) consist of 18 main and 18 small forts, with
intermediate batteries. The main forts are some 4500 yds. apart, and
11,000 to 12,000 yds. from the centre of the place. The typical
armament of a main fort is six 6-in. guns in three cupolas (one for
indirect fire), two 8.4-in. howitzers in cupolas, one 4.7-in. howitzer
in a cupola, six small Q.F. guns in disappearing cupolas. The total
armament of the place (all protected) is eighty-six 6-in. guns,
seventy-four 8.4-in. howitzers, eighteen 4.7-in. howitzers, 127 small
calibre Q.F. guns in disappearing cupolas, 476 small calibre Q.F. guns
in casemates for flanking the ditches. The "Sereth Line" will be
described later.

_Different Forms of Protection: Casemate, Cupola, &c._--The broad difference between casemates or shielded batteries and turrets and cupolas is that the former are fixed while the latter revolve and in some cases disappear. The casemate thus has the disadvantages that the arc of fire of the gun, which has to fire through a fixed embrasure or port-hole, is very limited, and that the muzzle of the gun and the port-hole, the weak points of the system, are constantly exposed to the fire of the enemy. The advantage of the casemate lies in its comparative cheapness and the greater strength of a fixed structure. It is well suited for barrier forts (fig. 53) and other analogous positions; and the Italians amongst other nations have so employed it at such places as the end of the Mont Cenis tunnel. Steel and iron casemates are also useful as caponiers for ditch flanking (fig. 55).

FIG. 55.]

_Turrets and Cupolas._--The difference between a turret and a cupola is that the former is cylindrical with a flat or nearly flat top and presents a vertical target; while the latter is a flattened dome, the vertical supports of which are entirely concealed. The turret appears to be little used. The object of both forms is at once to give an all-round arc of fire to the guns and to allow of the weak point of the structure, the port-hole and muzzle of the gun, being turned away from the enemy in the intervals of firing. Both usually emerge from a mass of concrete, which is strengthened round the opening by a collar of chilled cast iron about 12 to 15 in. thick.

Cupolas.

There are four types of cupolas, viz. (a) Disappearing, (b)
Oscillating, (c) Central pivot, (d) On roller rings.

(a) Disappearing cupolas are used chiefly for small quick-firing guns,
on account of the expense of the various systems. They can be used for
medium guns. The details of the best foreign systems are secret. (b)
The oscillating turret is a Mougin type, in which the turret is
supported in the centre by a knife-edge on which it can swing. The
oscillation is controlled by powerful springs. The effect of it is
that after firing, the front of the cupola with the port-hole swings
downwards under cover, and is held there until the gun is ready to
fire again. (c) Schumann's centre pivot is understood to be approved
in Germany. It has been adopted in Rumania and Belgium for howitzer
cupolas. It is only suitable for a single piece; d is strong and
steady--the best cupola for coast batteries; c and d are best for
rapid fire because they can be loaded without lowering. They are
suited for long guns.

The following types are illustrated as being generally representative
of the different classes of cupola.

Fig. 56 is a section of Messrs Krupp's typical cupola for one 6-in.
gun. The shield is of nickel steel, the collar of cast steel. A small
space is left between the cupola and its collar to prevent the
possibility of the shield jamming after being damaged. The guns are
muzzle-pivoting and thickened out near the muzzle by the addition of a
ring, so as to close the port as much as possible. The recoil is
controlled within narrow limits both to economize space and to prevent
the smoke from the muzzle from getting into the cupola. To facilitate
the elevation and depression of the gun (with muzzle pivotings the
breech has of course to be moved through a much larger arc than with
ordinary mountings) it is balanced by a counterweight. The cupola
rests on a roller ring and is traversed by a winch. It can be turned
through a complete circle in about one minute.

FIG. 57.--Gruson Spherical Mortar.]

Fig. 57 shows a Schumann shielded mortar (sphere-mortar,
_Kugelmorser_). In this case it will be observed that the cupola is
replaced by an enlargement of the encircling collar; and the mortar
(8.4-in. calibre) is enclosed in a sphere of cast iron, so as to close
completely the opening of the collar in any position.

Fig. 58 shows a Gruson cupola for one 4.7-in. Q.F. howitzer.

Fig. 59 shows a disappearing turret for an electric light projector.

Fig. 60 shows a Krupp transportable cupola for a 5.7-cm. gun. This is
drawn on a four-wheeled carriage, and when coming into action slides
on rollers on to a platform in the parapet. It weighs about 2-1/2 tons,
and with carriage and platform about 4 tons.

The mechanism of these cupolas is for the most part simpler than it
appears. Counterweights and hand winches are much in use for the
lighter natures of guns. The armouring of course keeps pace with
improvements in manufacture. The chilled cast iron first made popular
by the Gruson firm is now little used except for such purposes as the
collar round a cupola. Wrought iron, steel and compound plates for the
tops of cupolas have all been tried, the most recent Krupp-Gruson
designs being of nickel steel.

The sighting in some cases may be done by sights on the gun, with
suitable enlargements in the port-hole; in others by sights affixed to
the cupola itself (which of course can give horizontal direction
only); in others training and elevation are given in accordance with
the readings on electric dials, or instructions by telephone or
speaking tube. There is of course nothing unreasonable in this in the
case of indirect fire guns and howitzers, for if not firing from
cupolas they would be behind the shelter of some wood or quarry.

_Schumann's System: "Armoured Fronts."_--Lieut.-Colonel Maximilian
Schumann (1827-1889) of the Prussian engineers, who took a very
prominent part in the design and advocacy of armoured defences,
eventually produced a system which dispensed entirely with forts and
relied on the fire of protected guns. It consists of several lines of
batteries for Q.F. guns and howitzers in cupolas. He considered that
such batteries would be able to defend their own front, and the
infantry garrison was not to be called into action except in the case
of the enemy breaking through at some point of the line.

This system was actually adopted by Rumania (1889-1892) for the Sereth
Line. There are three routes by which the Russians can enter the
country across the Sereth river: through Focshani, Nemolassa and
Galatz. These three routes are barred by bridge-heads, those at
Focshani, the most important, being on the left bank of the Milkov, a
tributary of the Sereth.

The Focshani works consist of 71 batteries arranged on a semicircular
front about 12 m. long and from 8000 to 10,000 yds. in advance of the
bridges. The batteries are placed in three lines, which are about 500
yds. apart, and are subdivided into groups. The normal group consists
of 5 batteries, of which 3 are in the first line, 1 in the second, and
1 in the third. The first-line batteries each contain five small Q.F.
guns in travelling cupolas. The second-line batteries, each six small
Q.F. guns in disappearing cupolas. The third-line batteries have one
120-mm. gun in a cupola, and two 210-mm. spherical mortars with Gruson
shields. The immediate defence of the batteries consists of a glacis
planted with thorn bushes and a wire entanglement.

FIG. 58.--Cupola for 4.7-in. Howitzer.]

The fortification of these three bridge-heads are said to have cost
about L1,100,000. But the system of "armoured fronts" is never likely
to be reproduced, having been condemned by all authoritative
continental opinion. Its defects have been summarized by Schroeter as
follows: weakness of artillery at long ranges, want of security
against a surprise rush, the neglect of the use of infantry in the
defence, and the difficulty of command. This last is the most serious
of all. It is indeed difficult to conceive that any one should expect
half-a-dozen expert gunners, each shut up in an iron box with a gun,
to stop the rush of a thousand men, even by day. But imagine the
feelings of the gunner on the night of a big attack, alone in his box,
his nerves already strained by a preliminary bombardment and nights of
watching. He hears the sounds of battle all around; he knows nothing
of the progress of the attack, but expects everything, and feels every
moment the door of his box being opened and the bayonet entering his
back. No wise commander would submit his troops to such a test.

_Sir George Clarke and Unarmoured Systems._--Before leaving the subject of fortresses it is necessary to consider the ideas of those who, while recognizing the necessity for places permanently organized for defence, prefer to treat them more from the point of view of perfected field defences. It is to the credit of English military science that Sir George Clarke may be taken as the representative of this school of thought. His study of fortification, as he tells us, began with a history of the defence of Plevna (q.v.). He was led to compare the resistance made behind extemporized defences at such places as Sevastopol, Kars and Plevna, with those at other places fortified in the most complete manner known to science. From this comparison he drew the conclusion that the true strength of fortification does not depend on great masonry works intricately pieced together at vast expense, but on organization, communications and invisibility. In his 1907 edition he says:--

"Future defences will divide themselves naturally into the following
categories: (1) Permanent works wholly constructed in peace time and
forming the key points of the position. (2) Gun emplacements,
magazines and shelters for men in rear of the main line, all concrete
structures and platforms to be completed, though some earthwork may be
left until the position is placed in a state of defence. (3) Field
works, trenches, &c., guarding the intervals between the permanent
defences in the main line, or providing rear positions. These should
be deliberately planned in time of peace ready to be put in hand at
short notice. The essence of a well-fortified position is that the
weapons of the defender shall obtain the utmost possible scope of
action, and that those of the attacker shall have the minimum chances
of effecting injury."

FIG. 59.--Disappearing Turret for Searchlight.]

Infantry redoubts.

Since Sir George Clarke published his first edition in 1890 continental ideas have expanded a good deal. The foregoing statement as to the three categories of defences would be accepted anywhere now: the differences of opinion come in when we reach the stage of classifying under the first head the permanent works to be constructed in peace time. In most countries these would include forts with guns for the artillery duel, forts with safety armaments, fixed batteries with or without armour, and forts for infantry only. Sir George Clarke will have no armour for guns except in certain special cases of barrier forts. Heavy guns and howitzers requiring permanent emplacements (concrete platforms, &c.) must either be well concealed or be provided with alternative positions. The only permanent works which he admits are for infantry. They are redoubts of simple form intended for 350 or 400 men, with casemate accommodation for three-fourths of that number. Fig. 61 shows the design:--two rows of casemates, one under the front parapet, one under a parados; frontal musketry defence; obstacle consisting of entanglements, mines, &c., with or without escarp and counterscarp.

"The intervals (he says) between the infantry redoubts may be about
2500 yds.; but this will necessarily depend upon the conformation of
the ground. Where there are good artillery positions falling within
the sphere of protection of the redoubts, large intervals will be
permissible. Thus, in the case of an extended line of defence where
the ground offers marked tactical features, the idea of a continuous
chain of permanent works may be abandoned in favour of groups of
redoubts guarding the artillery positions. In this case, the redoubts
in a group might be distributed on a curve bent back in approximately
horse-shoe form."

FIG. 61.]

The keystones of the close defence of the fighting line in future will undoubtedly be these infantry redoubts, and therefore it is of great interest to compare with the above types two studies put forward by Schroeter (_Die Festung in der heutigen Kriegfuhrung_), one in his first edition in 1898 (fig. 62), and the other in the second in 1905 (fig. 63). In both these the defensive arrangements are merely trenches of field profile with entanglements, the command and the obstacle being less than in Sir George Clarke's work; and it will be noticed that in the 1905 type, published after the Russo-Japanese War, the plan is much less simple and arrangements for close flanking defence have been introduced. But these works of Schroeter's are merely infantry supporting points in a line which contains forts of the triangular type with guns, and armoured batteries, as well as a very complete arrangement of field defences and communications; while Sir G. Clarke's redoubts are the only permanent works giving casemate protection in the front line.

FIG. 62.]

The comparative merits of either design for an infantry redoubt are not of much importance. It is agreed that the main line of defence must consist of a more or less continuous line of field defences and obstacles, and that at some points in the line there should be infantry supporting points with bomb-proof protection capable of resisting big shells. The open question is, what additional works, if any, are required for the artillery, whether for the medium and heavy guns that will take part in the "artillery duel," or for the lighter natures that will help in the close fight and defence of the intervals. Is it best for the defenders to rely on armoured protection or on concealment for his guns?

Opposing views as to armour, gun positions, &c.

Official opinion outside England has certainly sanctioned armour, since all over the continent it is to some extent adopted in practice. National practice is usually based on the advice of the most distinguished officers of the day, and therefore it is unsafe to condemn it hastily. Sir George Clarke and those who are with him--and they are many, both in Great Britain and abroad--object entirely to armour. He says (_Fortification_, ed. 1907, p. 96): "The great advantage possessed by the attack in all ages has been the employment of a mobile artillery against armaments cribbed, cabined and confined by fortification. It is necessary to perpetuate this advantage?" Of course the effect of long-range weapons, in increasing the length of front that can be held by a given force, has given much greater freedom of action to the defence and this should be taken full advantage of.

FIG. 63.]

The argument as to the vulnerability of shielded guns is not at present strong. Sir George says (ib. p. 94), "If the high angle fire ... is ever to find a favourable opportunity, it will surely be against a cupola, the site of which can generally be determined with accuracy." On the other hand he says (p. 90), "During the long and costly experiments carried on at Bucharest in 1885-1886, 164 rounds were fired from the Krupp 21 cm. mortar at targets of about 40 sq. metres area" (about 430 sq. ft.) "without obtaining a single hit. The range was 2700 yds.; the targets were towers built upon a level plain; the shooting conditions were ideal, and the fall of each shell was telephoned back to the firing point; but it must have been evident to the least instructed observer that to attempt to group 6 or 8 shells on an invisible area 2 metres square would have been absolutely futile." These facts are adduced to prove that it is not necessary to give great thickness to concrete casemates, to resist successive bursts of shells in the same place; but surely they are equally applicable to cupolas. Again (p. 252), "The experience gained at Port Arthur was not altogether encouraging as regards the use of high angle fire. The Russian vessels in the harbour were sunk by opening their sea-valves.... Fire was subsequently directed upon them from 11 in. howitzers at ranges up to about 7500 yds. This was deliberate practice from siege batteries at stationary targets; but the effect was distinctly disappointing." The cupolas therefore can hardly be considered ideal targets: and the probability is that they would hold their own against both direct and indirect fire for a long time. There are other and stronger arguments against the general use of them, all of which are clearly set forth by Sir George Clarke.

The worst objections to the cupola are the military disadvantages of isolation and immobility, and the multiplication of mechanical arrangements. For a successful round from a disappearing cupola, the elevating and traversing arrangements, the elevating and loading gear of the gun, and the telephone communication, must all be in good order. At night the successful co-operation of the searchlight is also in many cases necessary.

The teaching of history is all against immobile mechanical defences. Initiative, surprise, unforeseen offensive action, keeping the besieger in ignorance of the dispositions of the garrison, and of what progress he is making: all these, with their influence on the morale of both sides, tend towards successful defences and do not point towards the use of armour.

It may further be said that the use of armour as a general rule is unnecessary, because a concealed battery is a protected one; and with the long ranges now usual for heavy guns and howitzers, there is not generally much difficulty about concealment.

In the opinion, however, of the present writer an exception must be made for guns intended to flank the line of defence, which would generally need bomb-proof over-head cover. Further, when we leave theory and come to the consideration of actual problems of defence, it will often be found that it is necessary to place guns in certain positions where good concealment cannot be got. In such cases some form of protection must be given if the guns are to engage the concealed batteries of the attack.

III. THE ATTACK OF FORTRESSES

In considering the history of siegecraft since the introduction of gunpowder, there are three main lines of development to follow, viz. the gradually increasing power of artillery, the systematizing of the works of attack, and in recent times the change that has been brought about by the effect of modern small-arm fire.

Cannon appear to have been first used in sieges as mortars, to destroy hoardings by throwing round stones and barrels of burning composition. Early in the 15th century we find cannon throwing metal balls, not only against hoarding and battlements, but also to breach the bases of the walls. It was only possible to work the guns very slowly, and archers or crossbowmen were needed in support of them, to drive the defenders from the crenellations or loopholes of the battlements. At that period the artillery was used in place of the medieval siege engines and in much the same manner. The guns of the defence were inaccurate, and being placed high on the walls were made ineffective by bad mountings, which did not allow of proper depression. The besieger therefore could place his guns close to the walls, with only the protection of a few large gabions filled with earth, set up on the ground on either side of the muzzle.

In the course of the 15th century the power of artillery was largely increased, so that walls and gates were destroyed by it in an astonishingly short time. Three results shortly followed. The guns of the defence having gained equally in effectiveness, greater protection was needed for the attack batteries; bastions and outworks were introduced to keep the besieger at a distance from the inner walls; and the walls were sunk in ditches so that they could only be breached by batteries placed on the edge of the glacis.

Early in the 16th century fortresses were being rapidly remodelled on these lines, and the difficulties of the attack were at once very much increased. The tendency of the assailants was still to make for the curtain, which had always been considered the weak point; but the besiegers now found that they had to bring their guns right up to the edge of the ditch before they could make a breach, and in doing so had to pass over ground which was covered by the converging fire from the faces of the bastions. Towards the end of the century the attack of the curtain was delayed and the cross-fire over the ground in front increased by the introduction of ravelins.

The slight gabion protection for the siege batteries was at first replaced by strong timber shelters. These were found inadequate; but a still greater difficulty was that of bringing up the siege guns to their positions, emplacing them and maintaining communication with them under fire. In addition to this, the guns of the defence until they could be overpowered (a slow process) dominated a wide belt of ground in front of the fortress; and unless the besiegers could find some means of maintaining a strong guard close to their batteries these were liable to be destroyed by sorties from the covered way.

Siegecraft before Vauban.

Gradually the whole problem of siege work centred round the artillery. The besiegers found that they had first to bring up enough guns to overpower those of the defence; then to advance their guns to positions from which they could breach the walls; and throughout these operations to protect them against sorties. Breaches once made, the assault could follow on the old lines.

The natural solution of the difficulty of approach to the battery positions was the use of trenches. The Turks were the first to make systematic use of them, having probably inherited the idea from the Eastern Empire. The soldiers of Christendom, however, strongly disliked digging, and at first great leaders like Bayard and Montluc had themselves to use pick and shovel, to give their men an example. In due course the necessity of the trenches was recognized, but the soldiers never took kindly to them, and the difficulty was dealt with in a manner reminiscent of the feudal ages, by impressing large bodies of peasantry as workmen whenever a siege was in contemplation.

Through the 16th and most of the 17th century, therefore, we find the attack being conducted by means of trenches leading to the batteries, and supported by redoubts often called "places of arms" also made by trench work. During this period the result of a siege was always doubtful. Both trenches and batteries were arranged more or less at haphazard without any definite plan; and naturally it often happened that offensive action by the besieged against the trenches would disorder the attack and at times delay it indefinitely. Fig. 64, taken from a late 17th-century print by de Fer of Paris, gives a good idea of the general practice of that day when Vauban's methods were not yet generally known.

Another weak point about the attack was that after the escarp walls had been strengthened to resist artillery fire as has been described, there was no clear idea as to how they should be breached. The usual process was merely an indiscriminate pounding from batteries established on the crest of the glacis. Thus there were cases of sieges being abandoned after they had been carried as far as the attempt to breach.

It is in no way strange that this want of method should have characterized the attack for two centuries after artillery had begun to assert its power. At the outset many new ideas had to be assimilated. Guns were gradually growing in power; sieges were conducted under all sorts of conditions, sometimes against medieval castles, sometimes against various and widely-differing examples of the new fortification; and the military systems of the time were not favourable to the evolution of method. It is the special feature of Vauban's practical genius for siege warfare that he introduced order into this chaos and made the issue of a siege under normal conditions, a mere matter of time, usually a very short time.

Vauban's teaching.

The whole of Vauban's teaching and practice cannot be condensed into the limits of this article, but special reference must be made to several points. The most important of these is his general arrangement of the attack. The ultimate object of the attack works was to make a breach for the assaulting columns. To do this it was necessary to establish breaching batteries on the crest of the glacis; and before this could be done it was necessary to overpower the enemy's artillery. This preliminary operation is nowadays called the "artillery duel." In Vauban's day the effective range of guns was 600 to 700 yds. He tells us that it was customary to establish batteries at 1000 yds. from the place, but that at that range they did little more than make a great deal of noise. The first object of the attack, therefore, after the preliminary operations of investment, &c., had been completed, was to establish batteries within 600 or 700 yds. of the place, to counter-batter or enfilade all the faces bearing on the front of attack; and to protect these batteries against sorties. After the artillery of the defences had been subdued--if it could not be absolutely silenced--it was necessary to push trenches to the front so that guns might be conveyed to the breaching positions and emplaced there in batteries. Throughout these processes it was necessary to protect the working parties and the batteries against sorties.

For this purpose Vauban devised the _Places d'armes_ or _lignes paralleles_. He tells us that they were first used in 1673 at the siege of Maestricht, where he conducted the attack, and which was captured in thirteen days after the opening of the trenches. The object of these parallels was to provide successive positions for the guard of the trenches, where they could be at hand to repel sorties. The latter were most commonly directed against the trenches and batteries, to destroy them and drive out the working parties. The most vulnerable points were the heads of the approach trenches. It was necessary, therefore, that the guard of the trenches should be in a position to reach the heads of the approaches more quickly than the besieged could do so from the covered way. This was provided for as follows.

The first parallel was usually established at about 600 yds. from the place, this being considered the limiting range of action of a sortie. The parallel was a trench 12 to 15 ft. wide and 3 ft. deep, the excavated earth being thrown forward to make a parapet 3 or 4 ft. high. In front of the first parallel and close to it were placed the batteries of the "first artillery position."

The attack.

While these batteries were engaged in silencing the enemy's artillery, for which purpose most of them were placed in prolongation of the faces of the fortress so as to enfilade them, the "Approach Trenches" were being pushed forward. The normal attack included a couple of bastions and the ravelin between, with such faces of the fortress as could support them; and the approach trenches (usually three sets) were directed on the capitals of the bastions and ravelin, advancing in a zigzag so arranged that the prolongations of the trenches always fell clear of the fortress and could not be enfiladed.

Fig. 65, taken from Vauban's _Attack and Defence of Places_, shows clearly the arrangement of trenches and batteries.

After the approach trenches had been carried forward nearly half-way
to the most advanced points of the covered way, the "second parallel"
was constructed, and again the approach trenches were pushed forward.
Midway between the second parallel and the covered way, short branches
called _Demi-parallels_ were thrown out to either flank of the
attacks: and finally at the foot of the glacis came the third
parallel. Thus there was always a secure position for a sufficient
guard of the trenches. Upon an alarm the working parties could fall
back and the guard would advance.

Trenches were either made by _common trenchwork, flying trenchwork or
sap_. In the first two a considerable length of trench was excavated
at one time by a large working party extended along the trench: flying
trenchwork (formerly known as flying sap) being distinguished from
common trenchwork by the use of gabions, by the help of which
protection could be more quickly obtained. Both these kinds of
trenchwork were commenced at night, the position of the trench having
been previously marked out by tape. The "tasks" or quantities of earth
to be excavated by each man were so calculated that by daybreak the
trench would afford a fair amount of cover. Flying trenchwork was
generally used for the 2nd parallel and its approaches, and as far
beyond it as possible. In proportion as the attack drew nearer to the
covered way, the fire of the defenders' small-arms and wall-pieces
naturally grew more effective, though by this time most of their
artillery would have been dismounted by the fire of the siege
batteries. It therefore became necessary before reaching the 3rd
parallel to have recourse to sap.

Sapping.

Sapping required trained men. It consisted in gradually pushing
forward the end of a narrow trench in the desired direction. At the
sap-head was a squad of sappers. The leading man excavated a trench 1
ft. 6 in. wide and deep. To protect the head of the trench he had a
shield on wheels, under cover of which he placed the gabions in
position one after another as the sap-head progressed. Other men
following strengthened the parapet with fascines, and increased the
trench to a depth of 3 ft., and a width of 2 ft. 6 in. to 3 ft. Fig.
66, taken from Vauban's treatise on the attack, shows the process
clearly. The sap after being completed to this extent could be widened
at leisure to ordinary trench dimensions by infantry working parties.

As the work at the sap-head was very dangerous, Vauban encouraged his
sappers by paying them on the spot at piecework rates, which increased
rapidly in proportion to the risk. He thus stimulated all concerned to
do their best, and reckoned that under average conditions he could
depend on a rate of progress for an ordinary sap of about 50 yds. in
24 hours.

It is interesting to compare the more recent method of sapping with
that above described (fig. 67 taken from the _Instruction in Military
Engineering_, 1896). It is no longer possible to place gabions in
position at the sap-head under fire. Accordingly the leading sapper
excavates to the full depth of 4 ft. 6 in., and the rate of progress
is retarded proportionately, so that an advance of only 15 to 30 yds.
in 24 hours can be reckoned on instead of 50. The head of the sap is
protected by a number of half-filled sandbags, which the leading
sapper throws forward as he goes on.

The nearer the approaches drew to the covered way, the more oblique
became the zig-zags, so that little forward progress was made in
proportion to the length of the trench. The approaches were then
carried straight to the front, by means of the "double sap," which
consisted of two single saps worked together with a parapet on each
side (fig. 68). To protect these from being enfiladed from the front,
traverses had to be left at intervals, usually by turning the two saps
at right angles to right or left for a few feet, then forward, and so
on as shown in fig. 69, the distance apart of these traverses being of
course regulated by the height from which the enemy's fire commanded
the trench.

Later stages of the attack.

The later stages in the attack are illustrated in fig. 70. From the third parallel the attack was pushed forward up the glacis by means of the double sap. It was then pushed right and left along the glacis, a little distance from the crest of the covered way. This was called "crowning" the covered way, and on the position thus gained breaching batteries were established in full view of the escarp. While the escarp was being breached, if it was intended to use a systematic attack throughout, a mine gallery (see _Mining_ below) was driven under the covered way and an opening made through the counterscarp into the ditch. The sap was then pushed across the ditch, and if necessary up the breach, the defenders' resistance being kept under by musketry and artillery fire from the covered way. The ravelin and bastions were thus captured successively, and where the bastions had been retrenched the same methods were used against the retrenchment.

FIG. 67.--"Deep" Sap.]

Vauban showed how to breach the escarp with the least expenditure of ammunition. This was done by making, with successive shots placed close together (which was feasible even in those days from a position so close as the crest of the covered way) horizontal and vertical cuts through the revetment wall. The portion of revetment enclosed by the cuts being thus detached from support was overturned by the pressure of the earth from the rampart. Ricochet fire was also the invention of Vauban. He showed how, in enfilading the face of a work, by using greatly reduced charges a shot could be made to drop over the crest of the parapet and skim along the terreplein, dismounting guns and killing men as it went.

18th-century principles of defence.

The constant success of Vauban must be ascribed to method and thorough organization. There was a deadly certainty about his system that gave rise to the saying "Place assiegee, place prise." He left nothing to chance, and preferred as a rule the slow and certain progress of saps across the ditch and up the breach to the loss and delay that might follow an unsuccessful assault. His contemporary and nearest rival Coehoorn tried to shorten sieges by heavy artillery fire and attacks across the open; but in the long run his sieges were slower than Vauban's.

So much a matter of form did the attack become under these conditions, that in comparing the supposed defensive powers of different systems of fortification it was usual to calculate the number of days that would be required in each case before the breach was opened, the time being measured by the number of hours of work required for the construction of the various trenches and batteries. It began to be taken as a matter of course that no place under any circumstances could hold out more than a given number of days; and naturally, when the whole question had become one of formula, it is not surprising to find that places were very often surrendered without more than a perfunctory show of resistance.

The theory of defence at this time appeared to be that since it was impossible to arrest the now methodical and protected progress of the besiegers' trenches, no real resistance was possible until after they had reached the covered way, and this idea is at the root of the extraordinary complications of outworks and multiplied lines of ramparts that characterized the "systems" of this period. No doubt if a successor to Vauban could have brought the same genius to bear on the actual defence of places as he did on the attack, he would have discovered that the essence of successful defence lay in offensive action outside the body of the place, viz. with trench against trench. For want of such a man the engineers of the defence resigned themselves contentedly to the loss of the open ground outside their walls, and relied either upon successive permanent lines of defence, or if these did not exist, upon extemporized retrenchments, usually at the gorge of the bastion.

It is curious that such experienced soldiers as most of them were should not have realized the fatal effect upon the minds of the defenders which this almost passive abandonment of line after line must needs produce. Even a civilian--Machiavelli--had seen into the truth of the matter years before when he said (_Treatise on the Art of War_, Book vii.): "And here I ought to give an advice ... to those who are constructing a fortress, and that is, not to establish within its circuit fortifications which may serve as a retreat to troops who have been driven back from the first line.... I maintain that there is no greater danger for a fortress than rear fortifications whither troops can retire in case of a reverse; for once the soldier knows that he has a secure retreat after he has abandoned the first post, he does in fact abandon it and so causes the loss of the entire fortress."

It must, however, be remembered that in those days when soldiers were mostly of a separate or professional caste, the whole thing had become a matter of business. Fighting was so much regulated by the laws and customs of war that men thought nothing of giving up a place if, according to accepted opinion, the enemy had advanced so far that they could no longer hope to defend it successfully. Once this idea had set in it became hopeless to expect successful defences, save now and then when some officer of very unusual resolution was in command. This is the real reason for the feeble resistance so often made by fortresses in the 17th and 18th centuries, which has been attributed to inherent weakness in fortifications. Custom exacted that a commandant should not give up a place until there was an open breach or, perhaps, until he had stood at least one assault. Even Napoleon recognized this limitation of the powers of the defence when in the later years of his reign he was trying to impress upon his governors the importance of their charge. The limitation was perfectly unnecessary, for history at that time could have afforded plenty of instances of places that had been successfully defended for many months after breaches were opened, and assault after assault repulsed on the same breach. But the same soldiers of the 17th and 18th centuries who had created this artificial condition of affairs, established it by making it an understood thing that a garrison which surrendered without giving too much trouble after a breach had been opened should have honourable consideration; while if they put the besiegers to the pains of storming the breach, they were liable to be put to the sword.

Peninsular War.