THE ORGANIZATION OF A DEFENSIVE POSITION.
The following remarks pertain to tactical or field fortification as
distinguished from provisional or permanent fortification. With the
latter the average line officer has little to do. With the former he
should be intimately familiar.
The principles herein discussed are to be considered as generally
applicable to portions of an extended defensive line to be occupied
by a force at least as great as a reinforced brigade. Smaller forces
rarely take up an intrenched position except for special purposes such
as: to delay the enemy in a defile, to protect bridges, stores or
munitions, etc., against raiding parties, in time of stress to hold out
against a larger force of irregulars until assistance comes, etc. In
all such special cases the tactics employed would be quite different
from those which would be applicable to a regular defensive position
occupied by a large force, and each problem would be dealt with in
accordance with the demands of the situation. Intrenched positions,
except in special situations, are usually impracticable for small
forces as, on account of their limited extent, they are easily turned.
The first requirement of a defensive position is that it shall be one
which the enemy must attack to accomplish his mission. If he can attain
his purpose by a turning movement or other maneuver the time spent in
organizing the position will be more than wasted. Another important
requirement is that the position be so selected and organized that the
enemy cannot hold the defenders in position with a small portion of his
force in their front while he turns their line with the bulk of his
command. Unless a purely passive defense is contemplated the aim of
each combatant should be to concentrate a superiority of force at the
critical point while holding the enemy in check at other points, for
herein lies the secret of success. Field fortifications exercise a most
baneful influence if they induce the defender to forego this purpose
or cause him to fail in the accomplishment. Under the usual assumption
that the attacking force is the stronger the defender’s organization
should be such that his intrenched troops can hold their front against
a superior number of the enemy, leaving the mobile reserves free for
the more active operations which must be relied upon to win decisive
victory. Field fortifications, then, are a means to an end. If used
indiscriminately, without a due regard for the strategical and tactical
requirements of the situation they may actually defeat instead of
promote the aims of the commander.
The general line to be occupied by a large force must usually be
selected from the map, in such manner as to meet the strategical and
tactical requirements of the situation. If the map is a good one (such
as the maps of the U. S. Geological Survey) the brigade sectors may
be selected therefrom. For the assignment of the smaller sectors, and
the organization of supporting points an examination of the ground is
absolutely essential. Any attempt to make such assignments from the
map alone would be very apt to result disastrously. Hence map problems
in defense should generally be limited to the assignment of brigade
sectors. Further details in the organization of a defensive position
should be studied as terrain exercises. The commanders of units from
a division down should make, either in person, or through a competent
staff officer, a reconnaissance of the sector assigned to the unit.
Engineer officers when available, may well be utilized for such
reconnaissance. The terrain should also be examined from the enemy’s
point of view (from the front) as such an examination will often afford
information that might otherwise be lacking.
Capt. Thuillier, R. E. (Principles of Land Defense) says, with
reference to the organization of a position where time permits of
a careful reconnaissance: “It is most necessary that the designer
should traverse and carefully examine the whole of the ground which
the attackers would occupy and that over which they must advance. The
points in which the latter’s artillery could advantageously be placed
should be noted.... The attacker’s communications both lateral and
from front to rear should be carefully studied as they will indicate
the points on which he can most easily concentrate his forces, and
thus point to the measures that must be taken to oppose them. All
ground hidden from the position of the defense should be noted and the
possibility of bringing on it an enfilade or indirect fire from other
points of the defender’s line ascertained. The facilities for attack or
for execution of trench work by the enemy will thus be discovered, and
the visibility or otherwise of the proposed sites for defensive works
made evident. Much valuable information will be obtained in this way
which could never be gotten from a study only of the defender’s ground.
The above procedure will also make plain what parts of a defensive
line may be safely neglected and what parts must be held in strength.
Generally speaking positions naturally strong may be left more or less
undefended, while weak points require special treatment. For instance
suppose the line to be defended has a length of ridge or a hill with
gently sloping open ground in front of it, and on the flanks broken
and rough ground with ravines, etc. If looked at from the defender’s
point of view only, the temptation will be to hold the ridge with
open ground in front as it so eminently lends itself to defense. But
if looked at from the attacker’s viewpoint it will be at once evident
that the latter would never make his advance over ground where he
would be at such a disadvantage, but would direct his attention to the
broken ground on the flanks where he might hope to make part of his
advance under cover. The open, easily defensible portion may therefore
be neglected, and the broken ground, though far less favorable for
defense, must be carefully defended.”
The matters to be considered in organizing a defensive position are:
the mission of the command, numbers and quality of troops, strength,
position and probable intentions of the enemy or of any supporting
troops in the vicinity, the nature of the terrain, the weapons of both
combatants, the efficiency of fire, artillery positions available for
both sides, ease of support, maneuver or retreat, what reinforcements
expected, if any, whether delaying or decisive action is contemplated,
time the position must be held, time available for preparation, etc.,
etc.
A field of fire at all ranges up to 2,000 yds. for the infantry, is
desirable in a decisive action. It is, however, practically never
obtainable naturally along the entire front of an extended defensive
position, and it is this fact that calls into play the skill of the
tactician and engineer in availing themselves to the utmost of the
natural advantages which the terrain affords, while avoiding its
disadvantages, and utilizing to the greatest possible extent all
available resources in time, labor, tools and materials.
So much depends on the conditions, purposes in view, relative qualities
of troops, armament, etc., that any set of rules as to the density
of occupation of a defensive position is apt to be misleading. If
the purpose is merely to deceive the enemy as to the strength of the
position and of the force occupying it and thereby cause him to halt
and deploy, thus losing time, a very long, thin line, dummy trenches,
etc., may be permissible, whereas such tactics would be little short of
suicidal in a decisive action.
It is by no means necessary nor even desirable that the fire trenches
of a defensive position should be in a line continuous along the
entire front, but it is wise to avoid deep echelons or offsets in
the line (except on the flanks, see post). An offset, reëntrant or
salient results in poor alignment which may present a weak flank to the
attacker’s infantry, or be subject to enfilade. There is frequently
danger from the fire of friendly trenches in rear, or the fire of
these trenches may be masked by those offset to the front of them.
Opportunities for mutual support may be sacrificed. If the exposed
flank of an advanced trench be attacked the troops in rear have a
tendency to surge forward out of control, in an endeavor to readjust
the line. Such offsets partake of the nature of salients in the line;
they possess most of the disadvantages of the latter with few of their
virtues.
The defenders then, will ordinarily be grouped by units at various
points along the line with intervals between. The areas occupied by
these groups are called “supporting points.”
Supporting points are the unit areas of the defensive position. They
may consist of a single knoll, a single nose convex toward the enemy,
a piece of wooded ground, a small village, suitable for defense by a
small combat unit, a large woods, a group of hills or noses, a large
town suitable for defense by a large combat unit, etc., etc.
The combat unit assigned for the defense of any supporting point will
vary with the size and importance of the area to be defended, its
relation to the rest of the line, the difficulty of organization,
proximity to a threatened flank of the general line, distance from
active supporting troops, etc. In our organization a battalion is the
smallest unit which ordinarily holds out a support, and it is the
smallest unit usually assigned to the occupation of a supporting point.
The location of the supporting points will depend on the terrain. In a
general way they occupy those portions of the ground which are convex
toward the front (front slopes of “noses” or of knolls) with ravines or
indentations between.
In field fortification closed works find little application. The front
is covered by a wide extent of rifle trenches, so disposed as to fire
on all portions of the terrain over which an advance of the enemy is
practicable. There should be a maximum development of frontal fire and
arrangements for mutual support by means of cross fire.
The general location of the line, and the area assigned to the unit
will fix approximately the position to be occupied. It must, of course,
be within the sector, but some leeway in the direction of depth is
allowed, so long as the unit does not unduly expose its own flank, or
those of the adjacent supporting points on either side, which are (in a
measure) dependent upon it for fire support.
It will thus be apparent that a unit may often be forced to organize
a supporting point in a locality which at first glance appears to
offer a very poor field of fire. This difficulty may be met by several
expedients:
1. The front should be covered by the cross fire of adjacent supporting
points, machine guns suitably placed, etc.
2. The trenches of the battalion should be so distributed as to cover
their own fronts and to cross fire as effectively as possible with the
other trenches of the battalion and those of the adjacent supporting
points to the right and left. A little careful study of the situation
will almost invariably reveal great possibilities in this way.
3. Where the field of fire or the view is unduly restricted by trees,
houses and other natural or artificial obstructions it is desirable
that these be removed. The burning of houses, crops, brush, etc.,
is usually inadvisable, as it renders the position very conspicuous
both during and after the conflagration. If the available time or the
equipment of tools and explosives does not permit the removal of such
obstructions by these means, covered approach thereto must be denied
by obstacles and strong cross fire. Ravines and hollows which might
afford shelter for the enemy should be covered with fire by a suitable
disposition of the trenches, and also rendered difficult of passage by
filling them with trees and brush, interlaced with wire if this seems
necessary.
4. Obstacles may be constructed in the foreground to hold the attacker
under the fire of the defense.
etc., etc.
For the purpose of mutual support and in order to permit of
concentration of fire it is very desirable that every supporting point
should be able to cross fire with those adjacent to it on either side.
Machine guns may be employed in covered emplacements, for surprise
at critical instants, or at places where a special reinforcement of
the infantry fire is likely to be required. Care should be taken that
machine guns are not _unnecessarily_ immobilized.
Trenches should usually be traversed, a traverse being placed every
squad or every two squads. As traverses in open trenches should not
ordinarily be built of higher relief than the parapet (or they will be
conspicuous) the protection afforded against oblique or enfilade fire
is not very great, unless they are introduced more frequently than at
every squad. The real advantage of traverses so far apart is that they
localize and reduce demoralization among the defenders. Communications
should be dug around traverses either in front or rear. Communications
around the front have the advantage of not reducing the space available
for riflemen. If time allows, head cover for the fire trenches should
be provided. If the trenches are close enough to the enemy to be in
danger from grenades, nets are sometimes provided as a protection
against these missiles. The trenches even if very close to the enemy
should be made as inconspicuous as possible. Great pains may well be
taken to conceal them from the view of the attacker, including view by
aero scouts.
Intervals are sometimes deliberately left between the larger
organizations on the defensive line in order to tempt the enemy to
attack the intervals, and thus expose himself to a counter-stroke of
the defender’s mobile reserves. Such tactics should be employed with
caution.
Even in the supporting point itself trenches should be discontinuous,
both laterally and in depth. As a rule the length of a single trench
should be limited to that necessary to accommodate a single company,
and if necessary to properly cover the assigned front even squad
trenches may be used. This allows great flexibility in making the
dispositions for effective fire, and is necessary to permit the best
adaptation of the trenches to the terrain, and the fullest development
of fire, as well as being in other ways desirable.
In very close country, where it is difficult to protect the intervals
by cross fire of adjacent supporting points, a practically continuous
line of trenches may be necessary to fully cover the front.
The entire front is divided into sectors or sections, assigned to
brigades, regiments and battalions. This simplifies command and insures
continuity of the defense.
The larger sectors (brigade and regimental) will usually have sector
reserves--the size of these reserves depending upon the tactical object
in view. A general reserve for the entire position is also provided.
If an active defense is contemplated (and this should usually be the
case) the general reserve will be made as strong as possible, the
least practicable number of troops being assigned to the firing line,
supports and local (sector) reserves. The relative numbers of troops to
be assigned to the various elements of the defense is one of the most
important as well as the most difficult details in the organization
of a defensive position. No rules for this can be laid down. An army
will seldom take up a defensive position unless it be weaker than its
adversary, either in number or quality of troops, armament, or some
other detail. In a purely passive defense field fortifications, by
increasing the resisting power of the defenders, permit the occupation
of a much longer defensive line than would be possible without their
aid. In an active defense the judicious use of fortification enables
the defensive line to be held with the minimum of force, thereby making
more troops available for the active, mobile reserves, with which
victory must be won. If the defender’s troops are dispirited or low in
morale, field fortifications give increased strength and confidence to
the troops occupying them and may enable them to successfully resist an
army which might defeat (or has defeated) them in the open. If field
fortifications do not economize in men for a force weak in numbers, or
give increased confidence to one which is low in morale, they fail in
their purpose and do more harm than good.
Supporting points will usually be organized by the troops which are to
defend them. Occasionally technical troops may be available for some of
the special tasks. All troops are provided with portable intrenching
and cutting tools, and for work of this class a certain number of
park tools will also be available. Local resources in the way of
labor, tools and materials should also be utilized if necessary. The
authorized allowance of tools of various organizations is subject to
changes which are set forth from time to time in orders.
The organization of a regimental sector may include some or all of the
following:
1. Assignment of troops to the first line and to reserves.
2. Division of the regimental sector into battalion sectors, and
assignment of troops thereto.
3. Selection and preparation of a covered station or stations for the
regimental commander.
4. Improvement of communications for movements of reserve, counter
attack, retreat, etc.
5. Selection of position or positions for machine guns, and
construction of emplacements. A portion or all of the machine guns may
be assigned to battalions in the first line, though this would not be
usual. Machine gun platoons should not be split.
6. Arrangements for communication by telephone, flag, etc. between the
different elements of the position.
7. Assignment of tasks to the reserves. Portions of the reserves may be
assigned to assist the battalions in the first line.
8. Selection and preparation of a suitable site for the regimental aid
station, and arrangements for the evacuation of the wounded.
9. Disposal of empty battalion ammunition wagons.
10. Arrangement for position fire of reserves, if contemplated.
etc.
The organization of a battalion sector (supporting point) may include
some or all of the following:
1. Assignment of companies to the firing line and battalion supports.
2. Selection of positions for and preparation of the fire trenches,
including traverses and head cover, if necessary, and if time is
available.
3. Selection of station or stations for the battalion supports and
arrangements for cover if natural cover is not available. Arrangements
for a second tier of fire to be occupied by the supports if desirable
and practicable.
4. Preparation of communications between the firing line and supports,
and adjacent trenches of the former, utilizing natural features of the
terrain to the greatest possible extent.
5. Selection and preparation of a suitable observing station for the
battalion commander.
6. Selection of position for the machine guns (if any are assigned to
the battalions) and construction of emplacements.
7. Construction of latrines at convenient places, as in returns of
communicating trenches.
8. Selection and preparation of a suitable site for the battalion
collecting station.
9. Selection of suitable sites for company kitchens.
10. Clearing the foreground, removal of all obstructions which
interfere with view and fire.
11. Preparation of obstacles to the enemy’s advance (covered by the
fire of the defenders). Ravines and hollows which might afford cover
to the enemy should be filled with trees, brush, etc., and wire
entanglements or other obstacles constructed to hold the enemy under
fire.
12. Measuring and marking ranges in the foreground.
13. Concealment of all works from view, including view by aero scouts
and observers for the hostile artillery.
14. Rough estimate of time required for the work contemplated and
assignment of men and tools to the various tasks.
etc.
It will frequently be the case that the situation does not demand, nor
the time available permit, the complete organization of the position
as outlined. In any case it is necessary to decide upon the relative
importance of the various tasks. The more important tasks are then
executed first, and the others as far as necessary, or as time allows.
It is often a matter of some difficulty to decide in any particular
case the exact relative importance of all the various tasks, as this
varies with the circumstances. In a general way it may be said that the
first requirement is a good field of fire, with ranges measured and
marked and the second, trenches for the troops on the firing line.
It will not always be practicable to secure a good field of fire at
both short and long ranges. Frequently one must be sacrificed to the
other and good judgment is required to determine which is of more
importance. In a decisive action effective fire at short and mid
ranges is most desirable, and ordinarily to be preferred when the
entire foreground cannot be covered. If a delaying action only is
contemplated, fire at the longer ranges may be all that is required.
In a decisive action the shorter ranges may be covered by the firing
line proper, while the longer are covered by position fire of troops
specially posted for this purpose.
The battalion supports should preferably be placed within 50 yds. or so
of the firing line, and rarely more than 150 yds. therefrom. If natural
cover is not available near at hand support trenches must be provided.
The supports should be conveniently located with a view to reinforcing
the firing line, preferably in one body (for each bn.) although they
may be divided if necessary. Covered communications to the fire
trenches are provided, utilizing the natural features of the ground as
far as possible.
The reserves are posted for use in protecting the flanks, or openings
in the line, or delivering counter attacks. Hence they should not be
too close to the firing line. They should be secure from fire, but it
is usually inadvisable (in field fortification) to provide artificial
cover. There will usually be no time for this, as reserves can be
better utilized otherwise, and the existence of artificial cover tends
also to diminish the mobility and initiative of the reserves. Natural
cover should therefore be sought. The reserves should not be too close
to a friendly artillery position, if likely to receive fire directed at
the latter. Sector reserves should generally be held in one body unless
the situation imperatively demands a division.
If the situation requires and conditions permit, supports and reserves
may be used for position fire, either in a second tier in rear of the
firing line proper or (in the case of the reserves) on a flank of same.
They may thus support the firing line at critical moments, force the
enemy to deploy at long range, or cover with fire portions of the
front which cannot be reached by the firing line proper. (See “The
Rifle in War,”--Chap. XVI.) It must be borne in mind, however, that
there is danger involved in immobilizing the reserves for the sake of
position fire. Once they are committed to action it will be difficult
to withdraw them. In any situation then, the advantages of position
fire must sufficiently outweigh the disadvantages of immobilizing
the reserves to warrant such procedure. It would seldom be wise to
immobilize the entire sector reserve for this purpose.
In deciding upon the location of the firing trenches the ground should
be carefully studied in order to obtain good results while avoiding
unnecessary labor in the way of clearing, communications, etc. In
removing trees from the front of a position it is seldom either
necessary or desirable to remove _all_ the trees. The undergrowth and
some of the smaller trees should be removed first. Most of the larger
trees can usually be left standing, being trimmed where necessary,
thus forming a screen for the position, rendering it less conspicuous.
Fallen trees should be removed. They may be used to fill ravines and
hollows which might otherwise afford cover to the attack.
All works should be carefully blended with the natural features of the
terrain to render them as inconspicuous as possible. Concealment is of
the utmost importance and great pains may well be taken to effect it.
The engineers should ordinarily be employed on works of general
importance or those which, by reason of their special training and
equipment, they are best qualified to perform. These may include:
demolitions, obstacles, cutting of heavy timber, construction or repair
of roads and bridges and improvement of communications in general,
measuring and marking ranges, special works such as head and overhead
cover, loop-holes, observing stations, splinter-proofs, etc., works in
the second line of defense if one there be, etc., etc.
The engineers should not be divided into many small parties (except by
their own officers) nor distributed along the entire front, as this
would result in a frittering away of their energies. It is permissible
that a company of engineers be assigned to each brigade sector under
the commander thereof. The tasks for the engineers should be indicated
by superior authority, but their distribution to best accomplish these
tasks should be left to the judgment of their own officers.
Provision should be made for security to the front and flanks during
the organization and occupation of the position. For this purpose
suitable outposts should be placed. The cavalry, by moving to the front
and gaining contact with the enemy, provides the greatest measure of
security, but an infantry outpost, or at least observers in front and
to the flanks of the line, should not in any case be omitted. Each
regiment or other unit may be directed to provide for the security of
its own front during the organization, or special provisions may be
made for the position as a whole.
Obstacles to delay the enemy _under fire_ should ordinarily be placed
not closer than 40 yards, nor more than 300 yards from the fire
trenches. If at a greater distance they are too readily destroyed by
the enemy. Wire entanglements are the most efficient form of obstacle,
as well as the easiest to construct. They should be concealed by tall
grass, hedges, branches of trees, a specially constructed glacis or
some other device.
_Organization of the flanks._ The flanks are ordinarily the most
vulnerable parts of an intrenched position. Unless these are secured
by impassable natural obstacles they must be artificially strengthened
by fortification, reserves, or both. When the assailant’s plan of
attack has been developed the reserves can, of course, be massed on the
threatened flank which will be also, in most cases, the locality most
favorable for counter attack. It is necessary, however, to make due
allowance for the time that will be required for the movements of the
reserves in an extended defensive position. If both flanks are “in the
air” (not secured by natural obstacles) the position is to that extent
a faulty one, and reserves may be required on both flanks. By making
the less vulnerable flank stronger by artificial means the reserves
on that flank may be reduced to a minimum, leaving the great bulk of
the mobile troops available for use on the more vulnerable flank which
is, naturally, the one more apt to be assailed. In the event of the
main attack falling on the stronger flank its natural and artificial
strength should be great enough to enable the troops defending it to
hold out until sufficient reserve can be brought to their assistance.
Refusing the line to provide security for a flank is objectionable in
that it immobilizes troops to face only to a flank which may not be
attacked, while presenting also a salient to the enemy. It is better to
provide protection against an enveloping attack by echeloning trenches
to the rear in short lengths. Where these trenches are visible from
the direction of enfilade it will usually be impracticable to provide
complete protection for the men when actually on the firing line, but
shelters may be constructed near at hand. These should be right angles
to the firing line, with their backs in the direction of enfilade, and
like the trenches to which they pertain, will be in short lengths and
echeloned. Communication is provided by means of oblique trenches. With
trenches thus echeloned enfilade fire can rake only short lengths of
trench, and its effect is thus greatly reduced. Every effort should
be made to conceal the works from view, especially from the flank, by
skilfully disposing them with reference to the natural features of the
terrain and by artificial means. If the terrain does not naturally
afford this concealment the parapets should be made low. The natural
features which screen the works should not be so close nor of such a
nature that they may be utilized by the attacker for cover during an
enveloping movement.
The proper organization of a flank calls for the highest skill of the
field engineer. Engineer troops when available, may well be assigned to
the complete preparation of this feature.
The following table gives the approximate times required for the
execution of the more usual classes of work, with the personnel and
tools required for different tasks. (See also F. S. R.) The times
stated are to be regarded as the best that may be expected with well
trained troops under reasonably favorable conditions. With green troops
or unfavorable conditions more time should be allowed.
-----------------+-----------------+-----------------+-------------
WORKS | PERSONNEL | TOOLS | TIME
-----------------+-----------------+-----------------+-------------
Simple standing |1 man per yd | Portable | 2 hours
rifle trench | | |
| | |
Simple overhead |1 man per yd | Park model | 2 hours, plus
covers | | | time for
| | | gathering
| | | and bringing
| | | up material.
| | |
Cutting down |6 in. diameter; | 2 axes or | 3 minutes
trees | 2 men | 1 jointed saw |
| | |
|12 in. diameter; | 2 axes | 15 minutes
| 2 men | 1 jointed saw | 10 minutes
| | 1 cross cut saw | 5 minutes
| | |
|18 in. diameter; | 2 axes | 30 minutes
| 2 men | 1 cross cut saw | 12 minutes
| | |
Clearing brush |20 men, 300 sq. | 5 axes and | 1 hour,
| yards | 5 billhooks | 30 sq. yds.
| | | per tool.
| | |
Abatis |6 men per | 1 axe, 1 saw, | 2 hours
|6 running | 1 billhook |
| yards | |
| | |
Wire entanglement|Preparing stakes;| 2 axes, 1 saw | 3 min. per
| 3 men | | stake
| | |
|Placing wire; | 1 maul, 3 wire | 1 hour
| 6 men per | cutters |
| 15 to 18 | |
| sq. yds. | |
| | |
Excavation in |1 man, 12 cu. ft.| Portable | 1 hour
medium soils, |1 man, 20 cu. ft.| Park model | 1 hour
2 hour reliefs | | |
By medium soils is meant those which can be excavated without the
use of a pick or pick mattock. The character of the soil greatly
influences the time required for excavation. In rocky soil the time
will be very greatly increased, and the task may be impracticable with
portable tools. Also the cutting tools of the infantry are suitable
only for light work, brush and small trees. The “simple standing
trench” referred to has a cross section area of about 7.5 sq. ft. and
1 running yd. can be constructed in about two hours with a portable
tool. This trench does not allow easy passage of men in rear of the
firers, and does not allow the latter room to sit down. The additional
room necessary for these purposes is obtained by the addition of about
10 sq. ft. to the cross section of the trench, converting it into the
“completed standing trench.” This requires about 2 hrs. additional
labor for each tool. The excavated earth may be wasted or part of it
added to the parapet. A 5 ft. length is a convenient task for one man
with a park (full sized) tool. Plows, when obtainable, are of great
assistance in the excavation of trenches in stiff soils. All the above
tasks (except wire entanglements) contemplate reliefs at periods not
exceeding two hours in length. If there be not enough men to furnish
reliefs additional time must be allowed for all tasks requiring more
than 2 hours time.
The following remarks are extracted from Instructions in Field Training
for the British Army. They are based upon the experience of the
European War. They are especially applicable to fortifications which
are to be occupied for a relatively long time and in relatively close
proximity to similar works of the enemy. They are also of special
interest as indications of the very great power of modern weapons and
the resulting necessity for concealment from view.
Trenches should be located so that they are not under observation by
hostile artillery. Possible observing stations on ground occupied by
the enemy should also be considered. This concealment is regarded as of
greater importance than an extensive field of fire.
A field of fire of 100 yds. will be sufficient if it cannot be extended
without loss of concealment. Obstacles in front of the trenches must be
carefully concealed as otherwise they will assist the enemy to locate
the trenches in rear.
A location for the trenches back of a slight rise or back of a second
hedge with obstacles hidden or entangled in the hedge in front has been
found to afford satisfactory concealment.
Modern artillery fire is practically continuous and the accuracy of
ranging phenomenal. Accordingly, the target must be reduced to the
smallest possible dimensions. This is best accomplished by making
the trenches as narrow and as deep as possible with practically no
parapet. Support trenches especially should be made deep. The support
trenches should be about 40 yds. in rear of and parallel to the fire
trenches with ample communications to the latter. To these most of
the men retire during a bombardment leaving as few as possible in the
fire trenches. Eighteen to twenty-four inches is sufficient width for
a trench. As this does not permit of the free passage of men along the
trench, communication is secured by means of a narrow trench about 15
yds. in rear of firing trench and connected to the latter at each
traverse by a narrow passage of the same depth (See Fig. X).
The fire trenches should be of the recessed traversed type whenever
time permits, traverses about 5 ft. wide at the base and 35 ft. center
to center (See Fig. X).
Surplus earth from trench excavation should be spread or sodded,
depending on the nature of the soil.
A bank of earth as a parados should be placed behind and close to
the trenches for protection against the back blast of high explosive
shells, provided this can be done without rendering the trenches
conspicuous. These parados should be sodded or otherwise concealed in
the same manner as the parapet. Dummy parapets may be constructed with
surplus earth.
Recesses under the parapet must be ceiled. If planking or other similar
material is available, time and trouble may be saved by laying the
ceiling for the recesses on the ground at the front of the trench, with
a good bearing at the ends, and then excavating the recess and throwing
the earth on top of the ceiling to form the inner part of the parapet.
The recesses serve to protect their occupants from shrapnel fire.
Elbow rests should be omitted or made very narrow. Most of the men
will prefer to make their own niches for the forearm. A device to
ensure proper aiming in the absence of lights during a night attack is
desirable.
Head cover and overhead cover are usually impracticable except at
points to be used as observing stations. They restrict the use of the
rifle and bayonet. Where head cover can be constructed to advantage a
continuous loophole is the best form.
The arrangement of trenches should be such as to develop as much
frontal fire as possible. Attacks by the enemy usually occur at short
intervals at night along the whole line. Under such conditions adjacent
sections of the line can give but little support to each other by
crossing fire. As cross and flanking fire is not to be relied on,
straight trenches are preferred.
Dressing stations and latrines may be provided in recesses in the
support trenches.
Drainage should be considered in laying out the trenches. When
practicable they should be drained to a low point in the locality. When
this is not practicable, sump holes must be provided in the trenches,
to be pumped or baled out.
[Illustration: FIG. X STANDARD FIELD TRENCH]
[Illustration: RECESSED AND TRAVERSED FIRING TRENCH]
Machine gun emplacements should be on the flanks of a section and as
well concealed as possible. They should not be unmasked too soon as
this exposes them to premature destruction by the hostile artillery.
Cover required for the reserves will depend upon their distance in
rear of the firing line and the enemy’s ability to search with fire
the ground in which the reserves are stationed. The possibility of
observation by aerial reconnaissance must always be considered.
Obstacles must be provided to check the enemy’s attempts to rush the
trenches. Barbed wire is the most effective obstacle, especially if
well concealed. The advantage of concealment, in addition to preventing
the use of the obstacles as range marks for the trenches in rear,
is that working parties are enabled to repair each night any damage
to the obstacles. This repair work must frequently be carried out
not over 100 yds. and occasionally not over 50 yds. from the enemy’s
trenches. High wire entanglements involving the use of posts extending
3’6" or 4' above the ground, are impracticable owing to the difficulty
of concealment and of repair. The driving of such posts is out of
the question when hostile trenches are in close proximity. Various
substitutes for these posts may be employed such as tripods constructed
of the limbs of trees lashed together, carried out and set in front of
the firing line at night, at intervals of about 15 feet. The tripods
are anchored to the ground and barbed wire laced between them. Any
light, strong, portable support for barbed wire entanglements is
acceptable.
Flare lights shielded on the side of the defender are useful.
If the flank of a line is to be refused, the trenches should be
echeloned to the rear. Otherwise the trenches on the flank will be
subject to enfilade fire, especially by heavy artillery at long ranges.
The following observations of the aeronauts will be of assistance to
those engaged in the construction of field fortifications:
1. A long continuous line of trenches is more visible than groups of
trenches.
2. Straight trenches are conspicuous.
3. Trenches across plowed fields are easily distinguished.
4. Straw spread in the bottom of trenches renders them conspicuous.
5. Trenches against hedges cannot be distinguished.
6. It is difficult to tell whether trenches or gun emplacements are
occupied.
7. Tracks to emplacements are easily distinguished.
8. Trenches should be covered with brush to hide deep shadows at bottom.
The operations on the European battle fields closely resemble the
methods which have hitherto been considered characteristic of sieges.
Sir John French says:
“In war as it is today, between civilized nations armed
to the teeth with the present deadly rifle and machine
gun, heavy casualties are absolutely unavoidable.
For the slightest undue exposure the heaviest toll
is exacted. The power of defense conferred by modern
weapons is the main cause for the long duration of
the battles of the present day, and it is this fact
which mainly accounts for such loss and waste of life.
Both one and the other can, however, be shortened
and lessened if attacks can be supported by a most
efficient and powerful force of artillery available;
but an almost unlimited supply of ammunition is
necessary, and a most liberal discretionary power as
to its use must be given to artillery commanders. I am
confident that this is the only means by which great
results can be obtained with a minimum of loss.”
Capt. Thuillier in his “Principles of Land Defense” states the
objects of field fortifications to be 1st, to increase to the fullest
possible extent the effective use of the defender’s weapons, and 2nd,
to restrict to the greatest possible extent the effective use of the
weapons of the attacker. These guiding principles are applicable to all
situations, and they should never be lost sight of in the organization
of a position. Col. Kuhn, Corps of Engineers, U.S.A., says: “The
highest expression of the art of field fortification consists in the
utilization of the _natural_ strength of the terrain in the most
advantageous manner with the minimum means including the avoidance
of its disadvantages. All natural screens, covers, obstacles and
communications have a distinct advantage over artificial creations,
not only in the relatively smaller amount of work required, but also
in the fact that the troops will, as a rule, advance from them more
readily than they will from purely artificial works.”
Sir John Jones (“Journals of Sieges in Spain”) says: “It should be
recollected that the number of men required to guard a position depends
less on the extent of its front than on the facility of access to the
several portions of it.” “This sentence,” says Thuillier, “contains the
very pith of defensive tactics.”
The foregoing remarks concerning the organization of a defensive
position may be illustrated by a few practical problems solved on the
map. The officer who desires, however, to become thoroughly qualified
for this most important duty, should practice the organization of
supporting points _on the terrain_.
_Note._ Details of construction of various intrenchments, shelters,
obstacles, and other works of field fortification, with the tools,
materials, personnel and time required, and the methods of conducting
the tasks are given in many textbooks, manuals and pamphlets on the
subject of field fortification, some of which are listed at the
beginning of this volume. (Chap I.)
PROBLEM NO. 1.
FIELD FORTIFICATION.
As part of an extended defensive line, facing generally west, your
regiment has been assigned the organization and occupation of the
sector EAST AND WEST RAVINE NORTH OF HILL 872, exclusive,--RAVINE
MARKED X-Y (See Fig. XI), exclusive. The first battalion will organize
a supporting point on 872 Hill, the 3rd battalion will be in reserve,
and the next regiment to the south will organize its north supporting
point on Bell Point, all as indicated upon the accompanying 6 inch
map. A platoon of the machine gun company has been attached to the 2d
battalion.
REQUIRED:
I. Location of the supporting point to be organized by
the 2d battalion, showing dispositions of troops
of the battalion. Division of the foreground,
indicating portions assigned to each supporting
point of your regiment.
II. Considering yourself now in command of the 2nd
battalion, give a detailed description of the
organization of your supporting point, with a
reasonable proof that it can be carried out in two
hours, which will be assumed as the time available
for work. Your companies are of 16 squads each
and have the authorized allowance of park and
portable tools. A platoon of 40 engineers has been
assigned to assist your battalion and their tool
equipment is ample to meet the requirements of any
reasonable task you may see fit to assign to them,
but engineer tools will be used by engineers only.
There is also assigned to assist your battalion one of
the reserve companies with its complete tool equipment.
III. In the assignment of work to the engineers, what
considerations governed your decision?
IV. Indicate all dispositions, works etc., upon the
accompanying map, employing conventional signs.
_Note._ In this problem (and the one following) each company of
infantry is assumed to have 16 squads of 8 men each, available for
work. Each company is assumed to have 64 portable digging tools
(shovels and picks), and its allowance of park digging tools (full
size, commercial pattern) is 24 shovels and 12 picks. Each company
has 16 portable wood and brush cutting tools (hatchets and machetes)
and its allowance of park wood cutting tools (full size, commercial
pattern) is 1 cross cut (2 man) saw and 2 axes.
_Solution._ (See Fig. XI).
_Requirement I_: 1st Battalion to right supporting point; to organize
supporting point on 872 hill; to cover the foreground from east and
west ravine north of hill 872 exclusive to ravine south of the Sharp
House exclusive, crossing fire with left supporting point of next
regiment on the right and with supporting point number 2 as far as and
across Salt Creek at the loop obtruding into the foreground in front of
Zalinsky House.
2d Battalion to the left supporting point; to organize 855 hill and
adjoining noses; to cover the foreground from ravine just south of
Sharp House inclusive to ravine X-Y exclusive; crossing fire with 1st
supporting point as far as and beyond the bridge over Salt Creek and
with right supporting point of next regiment on the left across X-Y
ravine.
Colonel directs that at least two companies in each battalion be placed
on the firing line, more if a closer examination of the ground seems
to justify, but that at least one company in each battalion be held in
support.
_Requirement II_: The front assigned to the battalion is about six
hundred yards; the foreground is generally open and concave for a
distance (from Salt Creek to the east) of nearly six hundred yards,
except in the center of the front where Salt Creek makes a loop into
the foreground; here the field of fire is much interfered with by the
growth along Salt Creek (the steep banks of which offer excellent
opportunities for the approach of an enemy screened by the trees), the
convex nose on which the Zalinsky House is located and the building and
trees on that nose. The enemy, taking advantage of these conditions,
could approach to within a very short distance of the firing line
unless prevented by adequate cross fire. This is the weak portion of
the line and must be well attended to. A fire trench just west of the
Zalinsky buildings could cover the loop, but it is only about 100
yards from the banks of the creek, which avenue of approach can not be
entirely denied to the enemy; this is too close and such a location is
to be avoided if possible. A location east of the convex Zalinsky House
nose is therefore desirable. Just in front of the timber line along
Sheridan ridge the conditions for firing trenches are nearly ideal.
A company trench can be conveniently located on 855 hill as shown on
map; this trench with 1 foot command can cross fire in front of 1st
supporting point as far as the bridge and all along Salt Creek bottom
from the creek to immediate front of the fire trenches of the 1st
supporting point. To the front the fire of the trenches is interfered
with by the buildings, orchards, and trees along Salt Creek, all of
these can and must be removed, there is dead space however from the
house to Salt Creek which can not be obviated and must be covered
by heavy cross fire. The location of the left company of the right
supporting point crosses fire, when timber is removed, across the loop
in the creek, sweeping the old corn field on the west side of creek;
the machine gun platoon, located as shown, sweeps by an enfilading fire
the whole line of Salt Creek in front of the regiment as far as the
bridge and, when the trees are removed, the bottom of Salt Creek and
both its banks from A to B. Such use of the machine guns, to reinforce
a weak portion of the line, is desirable in this case. This cross fire
from the machine guns is reinforced by the platoon of G Company, and
the right platoon of H Company; the two center platoons of H Company
covering the front from the Zalinsky house to the X-Y ravine. The left
platoon of H Company in the existing trench to the left and rear of the
machine gun platoon, crosses fire with the right supporting point of
the next regiment on the left. (See Fig. XI.)
This development of the firing line is believed to be sufficient; the
squad trenches are, however, to be made at least 18 feet long and where
possible 20 feet long, and communicating trenches between companies and
squads to be prepared as far as possible for firing so that a heavier
firing line can be brought into play by feeding in the supports if
necessary.
The time for the organization of the supporting point is short but
the work behind the line is reduced very much by the ideal cover for
supports, collecting station, etc., offered by the deep ravine 30 yards
back of E Company.
The work to be done then, is reduced to the digging of fire trenches
(time will not allow the construction of head cover), arrangements
for lateral and other communications, clearing of the foreground and
marking out ranges. These duties are assigned as follows.
E Company has its own portable tools and the park digging tools of E
and F Cos. Twelve squads, each with 4 park shovels and 2 picks, dig 20
ft. trenches in two hours; four squads, each with 6 portable digging
tools, dig 18 ft. trenches; men not actually employed on this work use
the remaining portable tools and dig communications around the front of
the traverses which are left between squads. These communications are
of the same depth as the fire trenches.
H Company, which finds a platoon trench already constructed in a
suitable location, has its own portable and park tools. Six squads,
each with 4 park shovels and 2 picks, dig 20 ft. trenches in two
hours; six squads, each with 6 portable tools, dig 18 ft. trenches;
the remaining four squads, with the remaining portable tools, dig the
communications around the front of the traverses between squads, and a
communicating trench from the right of H Co. to the left of the G Co.
platoon trench.
G Company (3 platoons in support and 1 on the firing line) has its own
tools and the park digging tools of the reserve company. It will dig
30 yards of communicating trench forward to E Company’s fire trench,
and 65 yards of communicating trench laterally across the ravine to
the G Co. platoon trench. This latter communicating trench will be
made available for use as a fire trench in case of need, and will
therefore have the same profile as the fire trenches (7.5 sq. ft. cross
section) except for the northern 10 yards which cannot deliver fire,
(being under cover from the front) and has therefore a cross section
of 6 sq. ft. The platoon fire trench is dug by the platoon which is to
occupy it, this platoon has 16 park shovels and 8 picks. 55 yards of
communicating trench across the ravine is dug by eight squads, each
of which has 4 park shovels and 2 picks, this gives each squad about
20 ft. of trench, which they can complete in 2 hrs. The remaining
platoon (4 squads) each man with a portable digging tool, will dig the
communicating trench to E Co. fire trench (with observing station for
battalion commander) and the northern 10 yards of the communicating
trench across the ravine. The total length of trench for this platoon
to construct is therefore 40 yards or 120 ft. It has a cross section
of 6 sq. ft. and contains 720 cu. ft. Thirty-two men digging 12 cu.
ft. each per hour, will excavate 768 cu. ft. in 2 hours--just about
the allotted task, including the observing station. Reliefs are not
provided as the tasks last but 2 hours.
This leaves the engineers, F Co., and the company from the reserve for
the work on the foreground.
The work which it is desirable to do will be as follows: cutting trees
varying from 8 ins. to 16 ins. diam. along Salt Creek, from A to B
to C, 200 trees in all; scatter two straw stacks and a pile of cord
wood at D; destroy house, barn and outbuildings at Zalinsky’s; cut 20
four-inch orchard trees back of house, 14 in front of house and 6 large
trees, 60 small orchard trees to right front of house; 10 trees 8 in.
diam. at E; scatter pile of bricks; measure and mark ranges.
All the park cutting tools of the battalion are given to the reserve
company making (with its own) a total of 5 cross cut saws and 10 axes;
they have also their 16 portable cutting tools. One squad with two axes
is assigned to cut and trim the 10 large trees at E; 4 squads with
the portable tools are assigned to clear out a small amount of brush
immediately in front of the E Co. fire trench, very little work, and
then to assist in the orchards. Seven squads are given the remaining 8
axes and 5 saws and assigned to the task of cutting and trimming the
orchards and trees around the Zalinsky house. They will be assisted in
this work by the platoon with the portable cutting tools. There are
about 100 trees 6 ins. or less in diameter. One saw or 2 axes will cut
about 20 of these trees in an hour (see table, ante); all can easily
be cut and trimmed in the time available. The remaining squads of this
company will scatter the bricks and cord-wood in the yard.
The support company (F) with its own portable tools, some 6 pitch forks
and 2 axes (found at Zalinsky’s) and crowbars will remove the straw
stacks and tear down the cattle pens and the small outhouse near the
creek; scatter cord-wood, and assist the engineer detachment in tearing
down the large buildings.
To the engineers are assigned the tasks of destroying the house and
barn at Zalinsky’s and cutting the trees along Salt Creek at the loop.
All of the 200 need not be cut down, the view would be greatly improved
if only ¼ of them were cut but as many as necessary will be cut or
trimmed. They will average 12 inches. One cross cut saw will cut 12 per
hour or 24 in two hours; 10 will do the job assuming all must be cut
down, this will take twenty of the men; the other twenty are assigned
to the destruction of the house and barn. The total destruction of
these buildings by fire may not be possible in the time available,
and the smoke from the smouldering ruins would be more objectionable
than the buildings themselves. Moreover the barn is on a high stone
foundation and has an interior cross wall of stone. These would remain
standing after the conflagration as it would then be impossible to
destroy them by other means, and would afford cover to the enemy. Both
buildings will be closed as tightly as possible and a concentrated
charge of dynamite exploded in a central position in each. The men
will then with their picks and crowbars, blocks and tackle, etc., tear
down what remains, filling the cellars with debris so that they cannot
be used for shelter. The destruction of the buildings would require a
large amount of explosives, and the situation on the rest of the line
would determine whether or not it could be spared for this purpose. If
not, lesser charges could be used on the framework of the buildings and
thus weakened they could be pulled down with block and tackle, men from
F Co. being called upon to assist if necessary.
The large trees along the creek bottom would, as far as possible, be
fallen into the bed of the stream, and all trimmings (branches) would
be placed therein, both to get them out of the field of fire and to
block the channel as far as possible, to render its passage or use as
cover the more difficult to the enemy.
_Requirement III_: The reason for the assignment, is that this work is
of general interest. The engineers were assigned to the destruction of
the house and barn because it was not thought wise to burn them and the
demolition by explosives and destruction by mechanical means require
articles of their equipment and technical skill in execution; they were
given the work of cutting down the trees along Salt Creek as most of
these are pretty large and the cross cut saws and other timber tools in
the hands of the engineers are better adapted to the work and the men
more skilled in tree felling than the infantry.
_Requirement IV_: (See Fig. XI.)
PROBLEM NO. 2.
FIELD FORTIFICATION.
_General Situation._ (See 1 inch Geological Survey and 6 inch Maps.)
Missouri, Blue and Kansas, Red, are at War. A Blue Army Corps is
invading Kansas. On June 8th the 1st Blue Division, in the advance,
near Lowemont, was being attacked by superior Red forces.
_Special Situation, Blue._ The 2nd Blue Division was following the
first and was disposed as follows on the morning of the 8th: the 10th,
11th, 12th and 13th Inf., 1st Bn., 1st L. A., 1st Sq., 1st Cav., Co.
A, 1st Engrs., 1st Amb. Co., had crossed the Terminal Bridge and were
marching on Lowemont to support the 1st Division, which had been
attacked by superior Red forces estimated at 2 divisions, on the
afternoon of the seventh of June. The head of this detachment at
8:30 a. m. was on the Atchison Pike at the railroad crossings east
of Salt Creek village. The remainder of the Division was expected to
reach Leavenworth late that afternoon via the Terminal Bridge. The 3rd
Division was expected to reach Leavenworth on the morning of the tenth
of June.
At 8:30 a. m., June 8th, Gen. A, commanding the detachment of the 2d
Division, received the following message at Atchison Hill, from Gen. X,
1st Division (who is in command of all the Blue forces in Kansas until
the arrival of the Corps Commander).
Wireless: 8 MILE HOUSE, near LOWEMONT, KAN.,
8 June,’16, 8:15 a. m.
To Gen. A:
The enemy resumed his attack in great force at daybreak. A heavy Red
column, estimated at about a division, is reported moving east toward
KICKAPOO. I shall retire at once via the ATCHISON PIKE and ZIMMERMAN
ROAD to a defensive position west of LEAVENWORTH. Place your detachment
in position on the line SHERIDAN RIDGE--ATCHISON HILL, to cover our
withdrawal.
X,
Major General.
Gen. A decides to occupy a position with his right resting on the
Missouri River, and running thence south along the front slope of
Sheridan Ridge. He directs the 10th Inf. to occupy and intrench the
sector Missouri River to Millwood Road, inclusive, 11th Inf., from the
Millwood Road, exclusive, to Bell Point, exclusive, &c., &c. (See Fig.
XII.)
_Requirements_:
I. As commander of the 10th Infantry, what assignments
of troops and divisions of sectors do you make?
You are in command of the 1st Bn., 10th Inf. One
company of the reserve bn. and a half company of engineers
have reported to you to assist in the organization of
your sector, as assigned in Requirement I. All (Inf)
companies are of 16 squads and have their usual equipment
of portable tools, with the authorized allowance of
park tools. The engineers have tool equipment ample
to execute any reasonable task that may be assigned them,
but have none available for issue to the infantry.
[Illustration: Fig. XI]
After arrival in the position information received indicates
that three hours will be available for preparation.
II. Your general plan for the organization of your supporting
point, including a statement of the works you deem
necessary.
III. Your assignment of the men and tools to the different
tasks, and proof that your plan is practicable in the
available time.
IV. Indicate to scale on the accompanying map all works
undertaken. (Works executed by the 1st Bn., only.)
_Solution._ (See Fig. XII.)
I. The regimental commander of the 10th Infantry decides to place
two battalions on the line, and one in reserve. The 1st Bn. (with 1
plat. Mach. Gun Co.) is assigned to the sector Missouri River to large
ravine flowing into Salt Creek and heading up toward the Shafer House,
inclusive; the 2d Bn. is assigned to the sector, ravine exclusive to
Millwood Road, inclusive. The 3d Bn. is held in reserve.
II. The bn. commander decides to place 2½ companies on the line, and
to hold 1½ companies in local support. Half of A Co. is placed on the
nose forming the extreme northern end of the Sheridan Ridge. This is a
sort of natural fort, slightly hollow on top, with very high command,
and precipitous side slopes. In its front Salt Creek forms an obstacle
passable with considerable difficulty by infantry only. The position is
practically inaccessible from the front, and lying within 200 yds. of
the river it forms an excellent flank for the Sheridan Ridge position.
To the northwest lies a plain, perfectly open to view for some 600
yds., which can also be covered by artillery fire from the Blue
position. The slopes in front of the position are covered with trees.
The removal of a few rows of trees just below the crest will completely
open the field of fire, while the retention of the topmost trees will
serve to screen the position. The other half of A Co. is placed on
the front slope of the first nose south of the right flank, well up
the slope to command the foreground, and in such a position as to be
defiladed from the fire of the trenches to the left. The foreground of
this position is thickly covered with trees. These will be thinned out
to improve the field of fire, and the creek in the front will be made
impassable by felling trees into the backwater of the river. A half of
B Co. and all of C Co. are placed on the ridge extending to the south,
the right wing being placed well up on the high ground. The left wing
falls off to the low ground to the south, this flank being slightly
refused to cover the ravine forming the left of the bn. sector. By
placing this portion of the line well back on the high ground a double
advantage is secured, viz: the near field of fire, down to the creek,
is widened, and command is gained over a distant field (mid and long
ranges) which would be impossible were the trenches placed close to the
creek. When a certain amount of clearing has been done in the creek
bottom, these trenches will command the foreground to a distance of
nearly a mile, and will cross fire with the adjacent supporting point
in the approach to the latter. All fire trenches will be standing,
traversed trenches, provided with head cover. D Co. and half of B Co.
will be in local support, not intrenched, on the steep reverse slopes
of the position. Communicating trenches will be provided as indicated.
The machine guns will be placed on the high ground in rear of the left
from which position they can enfilade the two reaches of the creek in
the foreground. The bn. comdr’s. station will be placed on the highest
point of the knoll near the center of the position, as shown.
III. The fire line companies will dig their own trenches, and assisted
by 16 engineers, will provide head cover for same. They will use their
own portable digging tools, plus the park digging tools of the entire
battalion as well as the park digging tools assigned to the reserve
company.
Half of B Co. will prepare the communicating trenches and the bn.
comdr’s. station, using their own portable digging tools.
The mach. gun platoon will intrench itself, using park digging tools.
The half company of engineers, with the reserve company and Co. D,
(support) will clear the foreground, under the supervision of the
Captain of the engineer company. The more difficult tasks will be
assigned to the engineers, who will also prepare for destruction the
railroad bridge over Salt Creek on the right flank. The infantry
companies will use all the portable and all the park cutting tools of
the entire battalion, as well as those of the reserve company.
IV. See Fig. XII.
[Illustration: Fig. XII]