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ATTACK
OF
FORTIFIED PLACES.
INCLUDING
SIEGE-WORKS, MINING, AND
DEMOLITIONS.
PREPARED FOR THE USE OF THE
_CADETS OF THE UNITED STATES
MILITARY ACADEMY_.
BY
JAMES MERCUR,
_Professor of Civil and Military Engineering at the United States
Military Academy, West Point, N. Y._
_FIRST EDITION._
FIRST THOUSAND.
NEW YORK
JOHN WILEY & SONS,
53 EAST TENTH STREET.
1894.
COPYRIGHT, 1894,
BY
JAMES MERCUR,
West Point, N. Y.
_Right of Translation Reserved._
PREFACE.
In this work an attempt has been made to give in outline the best
modern methods of attack upon a fortified position by assault,
surprise, blockade, or siege; and also the detailed constructions of
those types of trenches, batteries, magazines, etc., etc., which seem
best suited to resist the fire of modern cannon, and to afford cover to
a besieging force.
It is not supposed that these types will be exactly copied in all
cases of actual practice, but that a wise discretion will be used in
modifying or combining them when necessary or desirable.
The constructions given are standard types, which have grown up by
combining the suggestions and the experience of the military engineers
of all civilized nations.
In selecting them I have drawn freely upon the textbooks of the schools
of military engineering at Chatham, Fontainebleau, Vienna, and Berlin,
as well as upon that of the late Professor Mahan, and the manuals of
Duane and Ernst.
The standard work of Gumpertz and Lebrun is frequently referred to
in “Military Mining”; and I am also under obligations to General H.
L. Abbot, Corps of Engineers, for the use of his unpublished notes
on the experimental mines at Willett’s Point, and the result of his
experiments upon the mining effects of shells charged with different
explosives.
J. M.
WEST POINT, N. Y.,
October, 1894.
INTRODUCTION.
Modern wars have been marked by sharp aggressive campaigns and great
battles in the open field, with few close and long-continued sieges.
The subject of siege-works has therefore attracted less popular
attention than was formerly devoted to it.
Fort Wagner, Vicksburg, Petersburg, Strasburg, Belfort, Paris, Plevna,
and Géok Tépé have shown, however, that at their respective dates
regular siege and mining operations were necessary to reduce either
permanent or field fortifications, if well equipped and defended.
The volume of fire delivered by the small arms and machine guns now in
use has made an open assault upon a well-supplied and well-defended
parapet, under ordinary circumstances, a hopeless undertaking, and has
necessitated more deliberate methods of attack.
The increased accuracy and penetration of modern cannon have rendered
obsolete many of the older methods of making regular approaches.
The newer constructions described herein, while giving greater
protection to the attack, are in general slower in their advance than
those previously used. This seems, however, to be an unavoidable evil,
which is mitigated only by taking advantage of every opportunity for
rapid advance offered by the errors of the defence.
It is not to be inferred that light field works and lines will in the
general case require for their attack a system of regular approaches;
but trenches and saps may be necessary for placing a battery or parapet
in a commanding position or one favorable for enfilade, or for giving a
covered approach over an exposed ridge; and their frequent employment
may be expected on future fields.
The destructive effect of grenades and Coehorn shells charged with
high explosives will doubtless in many cases check or stop the advance
of saps and trenches, and necessitate the use of blinded approaches
or mining-galleries in stubbornly contested sieges. The successful
application of mines at Géok Tépé will doubtless lead to their future
employment under similar circumstances. In the close attack upon a
shielded casemate or disappearing turret their use seems a necessity,
and when these defences are founded on rock or massive concrete
foundations, tunnelling operations by drilling and blasting will
be required. When practicable they will be expedited by the use of
power-drills driven by electricity.
It seems hardly necessary to add, that in sapping and mining
operations, as in all other branches of military engineering, all new
and improved inventions and methods which are applicable to the work on
hand will be used, as a matter of course.
The thickness of cover given in the text is based upon the penetrations
of the hostile projectiles.
For ready reference the maximum penetrations obtained in experimental
firing up to this date (1894) are given herewith, viz.:
Service bullets, copper or German-silver jacket, of 6.5 to 8 mm.
calibre, initial velocity from 2000 to 2550 f. s.:
At Muzzle. 100 yds. 900 yds. 2000 yds. 2730 yds.
Inches. Inches. Inches. Inches. Inches.
Pine wood 30 to 50 31 to 35 10 to 14 4.4
Seasoned oak wood 4 to 8 1.18
Untamped clay 60 to 78
Light sand 8 At 500 yds 17 inches.
330 yds. 440 yds. 880 yds. 2000 yds.
Inches. Inches. Inches. Inches.
Sand and earth 36 33 20 14 4
Steel and iron plate 0.31 to 0.38 0.28 0.24
Brick masonry 4½
Ice 63
Special steel-coated bullets, cal. 0.26 and 0.30:
Pine wood 55
Oak wood, seasoned 16 to 24
Beech wood 23 to 30
Sand 14
Special steel-coated bullets, cal. 0.236, vel. 2600 f. s.
Pine wood 62
French authorities give a muzzle penetration of 12 mm. = 0´´.473 in
iron plates for the Lebel bullet. No published experiments confirm this.
But few experiments seem to have been made to determine the penetration
of the projectile of field and siege guns into earth, and the published
data are very meagre and unsatisfactory.
The German Engineer’s Handbook (Pionier Taschenbuch, 1892) prescribes
the following thicknesses of parapets for cover against small-arm and
cannon fire, viz.:
----------------------------+------------+------------+------------+------------
| |Shrapnel and| |
Material. | Small Arm. | Splinters. |Field-guns. |Siege-guns.
----------------------------+------------+------------+------------+------------
Earth, sandy | 30" | 20" to 40" | 16½' | 23'
Turf and marshy earth | 60" | | |
Wood | 34" to 40" | | |
Brick masonry | 15" | | |
Brick masonry, single shot | | | 3' 4" |
Two steel plates each 0.32" | 0.64" | | |
Packed snow | 6' | | 26' |
Sheaves of grain | 16½' | | |
----------------------------+------------+------------+------------+------------
English authorities report craters of 21 feet length and 8 feet depth
blown out from an earth parapet by a single 200-lb. 8-in. howitzer
shell. They also state that the projectile of the pneumatic dynamite
gun has penetrated 40 feet of earth.
Owing to the rapid development of ordnance the current scientific and
military periodicals are in general the only source from which the
latest results in penetration, etc., can be obtained.
CONTENTS.
ATTACK OF FORTIFIED PLACES.
PAGE
INTRODUCTION. v
CHAPTER I.
THE ATTACK WITHOUT THE USE OF REGULAR APPROACHES.
ARTICLE
1. Blockade, 1
2. Surprise, 2
3. Defence against Surprise, 4
4. Assault, 4
5. Dispositions for an Assault, 5
6. Defence against an Assault, 7
7. Bombardment, 8
8. Defence against a Bombardment, 10
CHAPTER II.
SIEGE OR ATTACK BY REGULAR APPROACHES, PRELIMINARY CONSTRUCTIONS,
DEFINITIONS, ETC.
9. Siege, Progress of, 12
10. Tools and Appliances, 13
CHAPTER III.
TRENCHES, APPROACHES, PARALLELS, SAPS, SPLINTER-PROOFS AND PASSAGE
OF THE DITCH.
11. Trenches, 15
12. Parallels, 15
13. Approaches, 16
TRACING AND CONSTRUCTING PARALLELS AND APPROACHES.
14. Tracing Parallels, 17
15. Tracing Approaches, 18
16. Posting Working Parties, 18
EXECUTION OF PARALLELS AND APPROACHES.
17. Simple Trench and Flying Sap, 20
18. Construction by Simple Trench, 20
19. Construction by Flying Sap, 22
SPLINTER-PROOF COVER.
20. Splinter-proofs, 23
21. Bomb-proofs, 25
SAPPING.
22. Definitions, etc., 27
23. Full Sap, 28
24. Organization and Duties of Detachment, 28
25. Driving the Sap, 28
26. Breaking out a Sap from a Parallel, 30
27. Circular Place of Arms, 31
28. Shallow Sap, 31
29. Overground Approaches, 31
30. Double Sap, 32
31. Execution of the Double Sap, 32
32. Changing Direction of the Double Sap, 33
33. Breaking out a Double Sap from a Parallel, 33
34. Traversed Sap, 33
35. Traverse by Blinded Sap, 35
36. Crowning the Covered Way, 35
37. Trench Cavalier, 36
38. Former Methods of Sapping, 36
39. Passage of the Ditch, 37
40. A Wet Ditch without Current, 38
41. A Wet Ditch with Current, 40
CHAPTER IV.
BATTERIES, OBSERVATORIES, AND MAGAZINES.
42. Batteries Defined, etc., 42
43. General Requirements of Siege-batteries, 42
44. Construction of Batteries for Field-guns, 43
45. Batteries for Siege-guns and Howitzers, Elevated
and Sunken,--General Considerations, 44
46. Screens, 45
47. Exposed Sunken Battery, 46
48. Tracing the Battery, 47
49. Constructing the Central Passage and Splinter-proof, 48
50. Constructing the Battery, 49
51. Alternative Construction, 50
52. Splinter-proofs (additional), 50
53. Sunken Battery in a Parallel, 51
54. Battery behind Crest of a Hill, 53
55. Batteries on Sloping Ground, 53
56. Embrasures, 53
57. Observatories, 54
58. Drainage, 55
59. Mortar-batteries, 55
60. Magazines, 57
61. Cover for Magazines, 58
62. Location of Magazines, 58
63. Construction of a Magazine subject to Direct Fire only, 60
64. Manner of Executing the Work, 61
65. Mined Magazines, 61
66. Elevated Magazines, 62
67. Precautions against Dampness, 63
CHAPTER V.
SIEGE OPERATIONS.
68. The Attack--Successive Steps, 64
69. The First Period, 65
70. The Investment, 65
71. Bringing Up and Posting the Besieging Force, 67
72. Fortifying the Camps, Parks, etc., 68
73. Distance of the Line of Investment from the Works, 70
74. Strength and Composition of the Besieging Force, 70
75. The Point of Attack, 73
76. First Artillery Position, 75
77. Opening Fire, 76
78. Plan of Attack, 78
79. The First Parallel, 78
80. Opening the Parallel, 80
81. The Second Artillery Position, 81
82. Counter-batteries, 82
83. Enfilading-batteries, 82
84. Breaching-batteries, 83
85. Batteries of Rifled Mortars and of Howitzers
for Vertical Fire, 83
86. Opening and Conduct of Fire from Second Artillery
Position, 83
87. Musketry Fire, 84
88. The Advance from the First Parallel, 84
89. The Second Parallel, 85
90. The Third Period, 86
91. Capture and Crowning of the Covered Way, 87
92. Breaching the Scarps and Counter-scarps, 88
93. Capture and Crowning of the Breach, 89
94. The Attack by Sap, 91
95. Additional Operations Necessary in the Attack of
an Intrenched Camp, 91
96. Occupation of a Conquered Place, 93
97. Vauban’s Maxims, 94
98. Journal of the Attack, 97
CHAPTER VI.
THE DEFENCE.
99. Preliminary Considerations, 98
100. Garrison, 99
101. Armament, 100
102. Ammunition, Provisions and Supplies, 101
103. Sanitation and Hygiene, 101
104. Preparations for Defence, 101
105. Defence during the First Period, 103
106. Opening of Artillery Fire by the Defence, 104
107. Defence during the Bombardment and Assault, 105
108. Defence during the Second Period of the Siege, 106
109. Defence during the Third Period of the Siege, 107
110. The Capitulation, 109
111. Journal of the Defence, 110
CHAPTER VII.
PARKS, DEPOTS, SHELTERS AND HUTS, KITCHENS, OVENS, SINKS, LATRINES,
WATER-SUPPLY, ETC.
ARTICLE PAGE
112. Parks and Depots, 111
113. Shelters and Huts, 113
114. Kitchens and Ovens, 114
115. Latrines, Sinks, etc., 115
116. Water-supply, 116
_PART II._
MILITARY MINING.
CHAPTER I.
NOMENCLATURE AND THEORY.
ARTICLE PAGE
1. Definitions, 119
2. Theory of Explosion, 120
3. Form and Volume of Crater, 121
4. Relation between Volume of Crater and Charge, 122
4. Miner’s Rule, 122
5. Charge for One Cubic Yard, 123
6. Rule for Common Mines in Ordinary Earth, 124
7. Overcharged and Undercharged Mines, 125
7. Deduction of Formula for Charge, 125
8. Relation between Charges of Common and Over- or
Undercharged Mines, 127
8. Charge to Produce a Camouflet, 128
9. Radius of Rupture, 128
10. Theoretical Value of Radius of Rupture, 129
11. Values Adopted by English Authorities, 131
12. Theoretical Value Too Small, 131
13. High Explosives, 131
14. Experimental Determinations, 131
15. Choice of Explosives, 132
16. Probable Advantage of High Explosives for
Overcharged Mines, 133
17. Relative Advantages and Disadvantages of Gunpowder
and High Explosives, 134
CHAPTER II.
PRACTICAL OPERATIONS AND DETAILS.
18. Tools and Appliances, Description of, 136
GALLERIES AND SHAFTS.
19. Dimensions of Galleries and Shafts, 138
20, 21. Shaft and Gallery Linings, 139
22. Shaft and Gallery Frames, 140
23. Dimensions of Pieces of Frames, etc., 141
24. Relative Advantages of Cases and Frames, 141
25-28. Sinking Shaft by Frames and Sheeting, 141
29. Precautions Needed, 144
30. Partly-lined Shafts, 145
31. Driving a Gallery with Frames and Sheeting, 145
32. Use of False Frame, 146
33. Use of Shield, 147
34. Inclined Galleries, 147
35. Position of Frames, 148
36. Partly-lined Galleries, 148
37-39. Change of Direction of Galleries with Frames
and Sheeting, 148
38. Change of Slope, of Galleries, 149
40, 41. Returns, 150
42, 43. Maps and Drawings, 151
44, 45. Sinking a Shaft with Cases, 152
46-48. Driving a Gallery with Cases, 153
49. Change of Direction of Galley Lined with Cases, 154
50, 51. Change of Slope, 7 Galleries Lined with Cases, 155
52. Shafts à la Boule, 156
53-55. Blinded Galleries, 156
56. Rate of Advance of Galleries, 157
VENTILATION OF MINES.
57. Sources of Deleterious Gases, 158
58. Ventilation by Forcing in Air, 159
59. " by Exhausting Air,159
60. " by Assisting Natural Ventilation, 160
61. " by Use of Masks, etc.,160
MINE-CHAMBERS.
62. Form, Size, and Location of Chambers, 160
LOADING AND FIRING MINES.
63. Preparing the Charge, 161
64. Distribution of Fuses in Charge, 161
65. Character and Construction of Fuses, 163
66-68. Electric Fuses, 163
69. Placing the Fuses in the Charge, 164
70. The Fuzes in Frozen Dynamite, 165
71. Placing the Charge, 165
72. Tamping Mines, 166
73. Firing Mines, 166
CAMOUFLETS BY BORING.
74. In Favorable Soil, 167
75. In Stony Soil, 168
CHAPTER III.
ORGANIZATION AND TACTICS OF MINES.
76. Organization of Mines, 169
77. The Attack, 169
78. The Lodgment, Galleries, Transverses,
Listening-galleries, etc., 170
79. Avoid Exposing a Flank, 171
80. Use Overcharged Mines, 171
81. The Defence, 171
82. Conditions to be Fulfilled, 171
83. System of Galleries Used, 172
84. Use Undercharged Mines, 172
85. Shaft Mines, 172
MINE TACTICS.
86. Tactics Derived from Results of Experience, 172
87. Todleben’s Rules, 173
88. The Attack, 173
89. The Defence, 174
90. Advantage Lies with Besieger, 176
BREACHING BY MINES.
91. Preparation of Wall Location and Size of Charge, 176
92. Galleries behind Counter-scarps, 177
93. Galleries through Scarp, 177
CHAPTER IV.
BLASTING AND DEMOLITIONS.
94-97. Definitions; Tools and Appliances, 178
98. Tamping Blasts, 179
99. Determining the Charge, 179
100. Precautions, 180
DEMOLITIONS.
101. Deliberate Demolitions, 180
102. Hasty Demolitions, 181
103. Houses and Magazines, 181
104. Walls, 181
105. Stockades, 182
106. Bridges, 182
107. Tunnels, Canal-locks, etc., 183
108. Railroads, 183
109. Rolling-stock, 184
110. Excess of Explosive to be Used, 184
ATTACK OF FORTIFIED PLACES.
CHAPTER I.
THE ATTACK WITHOUT THE USE OF REGULAR APPROACHES.
=1.= A fortified position may be taken by _blockade_, _surprise_,
_assault_, _bombardment_, or _siege_.
A =blockade= consists in so surrounding a place and closing its
communications as to keep the garrison from receiving reinforcements,
provisions, and supplies sufficient to enable it to continue the
defence and to avoid starvation.
The object of the attacking force is, in general, to completely close
all communications between the garrison and the exterior; but this
is not always possible, nor is it necessary in all cases, since such
obstruction of communications as will reduce the incoming supplies
below the necessary expenditures of the garrison will ultimately
exhaust its stores.
An efficient blockade, continued long enough, will consequently reduce
any place.
Whether it is advisable to attempt to reduce a place by blockade will
depend upon the time which will probably be taken in its reduction,
the force required for surrounding it, and repelling sorties from
the interior or beating back a relieving army, and the expense in men
and materials of taking the work by other methods. Blockades are more
effective in reducing cities and towns than in taking places occupied
only by a military garrison, since the presence of a large number of
non-combatants in a place rapidly exhausts its store of provisions,
renders epidemics more likely to break out, and by the suffering and
misery resulting demoralizes the garrison, unnerves the commander, and
eventually causes its fall. This justifies the apparent harshness of
not allowing non-combatants to leave a beleaguered place.
The steps necessary for establishing the blockade are identical with
those taken for the investment in a regular siege and will be described
hereafter.
The capture of Paris in 1870-71 is one of the most recent and striking
examples of a blockade on a large scale.
SURPRISE.
=2.= A sudden and unexpected attack made upon a garrison
unprepared to receive it is called a =surprise=.
Formerly these were of not infrequent occurrence, but with modern means
of communication and methods of warfare they can hardly be looked for,
except in small affairs, where, through the weakness or exhaustion of a
garrison or the incapacity of its commander, the necessary and ordinary
precautions for their prevention are impracticable or are neglected;
or where they are brought about through treachery in the garrison, by
which the gates are opened to the attack.
Probably in the majority of cases attempts at surprise will be detected
and defeated; but as a success is usually valuable far in excess of the
losses suffered in its execution, promising opportunities for their
trial should not be neglected.
Surprises, when thought possible, are undertaken under the cover of
night, fog, or severe storms. The tactical disposition of the troops
is similar to that used in open assault, the columns being preceded by
ladder-parties for scaling walls, engineers for blowing down barriers,
etc., etc., according to the nature of the case, and followed by a
large reserve which is designed to hold any points captured by the
advancing columns. It is usually considered best to make simultaneous
attacks at several points, in order to confuse and divide the defence,
holding the main reserve nearest to the column which is expected to
succeed; but making provision also for promptly and fully supporting
any other party which may have forced an entrance into the work.
An entrance secured, consecutive points should be occupied and
held, preserving communication between them, and avoiding too great
dispersion of the troops, until a foothold is gained which can in all
probability be held against the defence. After this greater boldness
may be used in attacking important points within the place.
The complete capture of the work and its garrison cannot ordinarily be
expected, however, until daylight allows the systematic movement of the
attack throughout the place. In case of failure, any captured gate must
be held if possible until all the troops have retreated through it and
are covered by the reserves.
DEFENCE AGAINST SURPRISE.
=3.= The measures necessary to guard a fortified place against
surprise are of two classes. First, for its prevention, by use of all
the usual outposts and interior guards,--the organization and duties of
which need not be repeated here,--and of telegraphic and other signals
and communications with the surrounding country by which the approach
and movements of any attacking force may be made known before it comes
near the work.
Second, for its repulse, by so training and disciplining the garrison
that, upon the alarm being given, the parapets, batteries, etc.,
will be manned and all defensive measures will be taken before the
assaulting body can enter the work.
This will be accomplished by so thoroughly drilling the garrison in
its duties that each man will go at once to his proper station fully
equipped for his duties at any hour day or night, without confusion or
unnecessary excitement. The subsequent measures are the same as for
resisting any other assault.
ASSAULT.
=4.= By an =assault= is meant an open attack upon a position
by troops in line or column.
Formerly it was recommended to make assaults at early dawn, in order
to have the increasing daylight for securing the results of victory;
more recently night attacks have been more strongly advocated in order
to diminish the losses from the fire of the defence while making the
attack, and the still greater ones which follow a repulse when, the
fire of the supports and reserves of the attack being suspended for
fear of injuring the retreating troops, the defence pours upon the
latter the full close and deadly fire of all its arms. Whether the
advantages of a night attack more than counterbalance the dangers
resulting from the confusion due to darkness is, however, a question
not yet settled.
Open assaults upon fortified positions, well manned and armed, have,
since the introduction of firearms, been considered the most bloody,
uncertain, and frequently the most unjustifiable operations in war.
With the introduction of machine and rapid-fire guns and magazine
rifles it may be considered as an established fact that a well-defended
line cannot be carried by an assault in front until its fire is
overpowered or its ammunition exhausted.
This conclusion, which has been drawn from attacks on field-works, is
still more positive in regard to attack upon works of strong profile
protected by deep ditches and other obstacles.
DISPOSITIONS FOR AN ASSAULT.
=5.= When an assault is ordered the tactical dispositions must be
so made as to keep the fire of the defence down to its lowest possible
limit, until the assailant can close in with the bayonet.
With this end in view, batteries are established sweeping the lines;
the assaulting columns, well supplied with ammunition, are formed where
protected from fire; working parties are arranged and provided with
such tools and appliances as are necessary for removing or overcoming
obstacles; and all preparations are made for simultaneous action by
the entire force.
It is manifest that to silence the fire of the work the attack must
have a marked preponderance of artillery arranged both for enfilade
and front fire upon the front of attack and the collateral works; and
that the batteries must be established, the fire opened, and the guns
of the defence silenced before the assault is made; and that this fire
must continue until the assaulting troops are so near the work as to
necessitate its discontinuance to avoid injury to them.
The working parties--carrying axes, saws, crowbars, and similar tools
which are needed for removing the existing obstacles; explosives for
blowing down gates, barriers, etc.; fascines, gabions, hurdles, etc.,
for crossing ditches, covering trous de loup, and other purposes; and,
when necessary, ladders for escalade--move forward with the columns of
attack; the latter must be so handled that, when the artillery fire is
suspended, they can keep down the fire of the defence with rifle and
light machine-gun fire.
Under cover of this fire the obstacles must be removed by the working
parties, and the first assault made by the troops detailed for this
purpose. With these troops should be a certain number of artillerists
provided with lanyards, friction primers, etc., to serve any guns that
may be captured, turning them against the defence.
A party of engineers provided with high explosives for blowing down
gates, etc., should follow closely behind the advance in case of an
escalade; they should also be provided with appliances for blowing up
magazines, etc., when possible, in case of a repulse. The gates being
captured and opened, the mass of the assaulting troops enter by them
and complete the capture of the place.
In case of repulse the retreat of the advanced parties is covered, when
possible, by the infantry fire of the reserves, and that of the latter
by the artillery, as in the advance.
DEFENCE AGAINST AN ASSAULT.
=6.= Permanent works being designed to be secure against
assaults and surprise, their guns of position are protected as well
as circumstances admit against the hostile artillery and infantry
fire. During the cannonade preliminary to an assault a wise discretion
must be used as to how much ammunition may be profitably expended in
replying to it, and how great an exposure of the men to the artillery
fire is justifiable. As a rule but little reply is made from the work.
The machine and rapid-fire guns should be withdrawn from the parapets
and be protected under bomb-proofs until the relaxation of the hostile
fire due to the near approach of the assault allows them to be run out
and to open fire. The infantry of the garrison is similarly handled,
being held under cover until the proper moment, then manning the
parapet and pouring a close, rapid, and deadly fire upon the assault.
The fire of the fronts directly attacked, both machine-gun and
infantry, will be directed principally at the assaulting columns and
working parties, the collateral works and fronts will, in addition to
pouring a cross-fire upon the assaulting columns, direct a large part
of their machine-gun fire upon the supports and reserves, while the
more powerful guns will generally direct their fire upon the hostile
artillery.
The troops not needed for manning the parapets are held under cover in
a central position as a reserve, to strengthen the force at any part of
the parapet or to meet and drive out any body of the enemy penetrating
the work.
Should the attack be repulsed, the most rapid and destructive fire
from all arms is directed upon the retreating troops with a view to
inflicting the greatest possible losses; but a counter-attack is,
as a rule, not attempted. When made, however, it should be limited
to making an advance upon one or both flanks to a position giving a
more effective fire upon the retreating troops, and retiring from
this position to the cover of the work as soon as the main attack is
completely repulsed and before the advanced troops become compromised
by a close engagement with the enemy.
BOMBARDMENT.
=7.= By a =bombardment=, technically speaking, is meant
a more or less continuous shell-fire upon a place with a view to
destroying magazines, buildings, materials, and supplies of all
kinds, in addition to inflicting the greatest possible losses upon
the garrison and producing among the inhabitants a state of terror
and unrest, frequently extending to mutiny, and finally causing the
surrender of the place.
The term bombardment is also frequently applied to a cannonade opened
upon a place to silence its artillery prior to an assault or during a
siege.
A bombardment promises success when the place is small and not
well provided with bomb-proofs, when the garrison is weak or of
bad morale, when the inhabitants are numerous and not in sympathy
with the garrison, or when the commandant is weak. A well-built and
well-equipped modern fort can hardly be reduced by bombardment with any
reasonable expenditure of time and ammunition; although the successful
use of torpedo-shells charged with high explosives will probably render
untenable works not designed to resist their effects.
When it is designed to reduce a place by bombardment a complete
investment is, as a rule, necessary only to prevent the withdrawal of
the non-combatants (a severe measure, but one frequently adopted), or
to insure the capture of the garrison upon the fall of the place.
The disposition of the troops is made for the special object in view.
The infantry, cavalry, and field artillery complete the investment,
if made; or, when the place is not invested, are concentrated at such
points as may be necessary to protect the artillery from any sorties
from the place, and to meet and repel attacks from any relieving force.
The artillery of larger calibre used for the bombardment proper should
consist principally of rifled howitzers and mortars, which are easier
to transport and more suitable for high-angle fire. As it is not
intended to dismount or silence the guns of the place by direct or
enfilade fire, an artillery duel should be avoided.
The batteries should be located, so far as possible, in places screened
from the artillery of the defence by undulations of the ground, etc.;
or, if this is impossible, by artificial screens as a cover from sight,
and by trenches as a protection from fire.
Considerable latitude is allowed in selecting sites for batteries. For
convenience of supply and unity of command they should be collected in
groups, the batteries of the groups separated by at least 100 to 200
yards; and the groups should be located, so far as other considerations
allow, near the main lines of communication.
If these groups do not entirely surround the place, they should, when
practicable, extend at least half way around, so as to bring a reverse
fire on all covers.
The fire, once opened, should continue night and day. If a
conflagration breaks out, a sharp fire of shells should be directed
upon it and its vicinity to prevent its extinction. Special efforts
should be made to blow up magazines and destroy shops, storehouses,
docks, roads, bridges, or other communications useful to the
defence; but, so far as is practicable consistently with these, an
attempt should be made to avoid injury to public monuments, museums,
antiquities, and works of art.
Bombardments are sometimes commenced and continued for a longer or
shorter time without the expectation of reducing the place, but to
destroy some of the constructions above mentioned or to prevent the
completion or arming of a work which it is intended to attack by other
methods. A slow bombardment may also precede the active cannonade
which prepares for an assault, or the systematic artillery attack of a
regular siege.
DEFENCE AGAINST BOMBARDMENT.
=8.= The defence against bombardment is frequently, from
necessity, strictly passive, and consists in so disposing the troops
and materials as to protect them under bomb- and splinter-proofs,
repairing damages to the latter and to magazines and parapets as
occasion offers; saving the ammunition of the place by firing only such
shots as promise to pay for themselves by the effect produced; and
reserving all the strength of the place to meet the subsequent attack,
if made.
When circumstances admit, a more active defence may be made, by a
strong garrison, by well-conducted sorties which may capture and
destroy the hostile guns and batteries and defeat and drive off their
supports.
Sorties of this kind may sometimes be profitably made against the
flanks of the attacking force, or against isolated batteries, even when
a general attack cannot be made. Opportunities for their use should not
be neglected.