GENERAL PRINCIPLES
“Each arm has its special characteristics and functions, and is
dependent on the assistance of others; the full power of an army
can be exerted only when all its parts act in close combination,
and this is not possible unless the members of each arm understand
the characteristics of the other arms.”
The above paragraph from _Field Service Regulations_, Part I.,
1909, aptly illustrates a principle which should be impressed
upon every serious machine-gun student, for the principles of
machine-gun tactics are based upon those of the arm with which they
are co-operating.
The machine gun cannot yet be regarded as a separate “arm” in our
service, nevertheless it possesses a power peculiar to itself;
and until this power is studied and thoroughly understood, the
principles that should govern its employment in the field cannot be
grasped, and consequently its effective use is dependent on chance
or accident, and for every success scored a dozen failures will
occur, any one of which may be fatal. The preceding chapter has
dealt with the peculiarities and power of the machine gun, and it
will be seen that it possesses the fire effect of the infantry arm
while it has several of the characteristics peculiar to artillery;
for instance, it is fired from a mounting by one man, and is moved
from position to position by draught or pack animals.
We have seen that the chief characteristic of the machine gun is
its power of delivering the “maximum fire from the minimum front”;
this fire is of great volume and is highly concentrated, while it
can also be made to sweep a wide lateral surface of ground. The
gun’s narrow frontage in action renders it easy to conceal, and
when discovered it presents a very small and difficult target to
the enemy’s riflemen; on the other hand, when once discovered if it
cannot be moved unseen to another position it is liable to suffer a
prolonged and concentrated fire from the widely scattered riflemen
of the enemy, to which it cannot effectively reply, and which must
in time cause loss. Again, its range being limited, it is powerless
against artillery except under special circumstances at effective
rifle range.
The general principles governing its tactical employment depend
upon three factors, viz. (1) the target, (2) the range, (3) the
position.
The volume and concentration of its fire necessitate a large
and vulnerable target, or ammunition will be expended without
adequate results. The first essential is therefore to obtain this
description of target and to avoid firing on others which may
present themselves.
A large and deep target might justify fire being opened at long
range, but such targets rarely present themselves on the modern
battlefield, and its vulnerability will partly depend on the
closeness of the range and partly on its formation. To obtain a
suitable target of this description _surprise_ is essential, and to
effect a surprise it will be necessary to conceal the gun and its
detachment in a well-chosen position.
Thus we see the three cardinal points for tactical success
are--suitable _target_ at close _range_ from a concealed _position_.
FIRE EFFECT
Napoleon’s maxim, that “fire is everything--the rest is of small
account,” is only applicable to the machine gun when the fire is
_effective_. Nothing is so useless and wasteful as ineffective
machine-gun fire, and the careful study of fire effect and how
to obtain the best results is imperative with this weapon. The
principles so ably stated in Colonel Mayne’s excellent book, _The
Infantry Weapon and its Use in War_, apply almost equally to
machine guns, and should be carefully studied by machine gunners,
particularly those chapters dealing with the employment of fire in
the field.
We have already seen that the range of the machine gun is
practically the same as that of the infantry rifle, but that the
beaten zone is only half the depth and about half the width of the
collective fire of infantry, partly owing to the rigidity of the
mounting, and partly to the fact that the human error is greatly
reduced by being concentrated in the person of a single individual,
instead of being spread over some 50 men of varying temperament,
nerves, and aiming powers.
In addition to these factors, the fire from machine guns is always
“collective” and “concentrated” unless deliberately dispersed
by the firer, while infantry fire is always “individual” and
“dispersed” unless controlled by fire discipline under a leader.
Fire discipline and fire control are in the hands of one man--there
is no need to point out the target to a scattered firing line,
and there is no delay in passing orders down the line, or in the
setting of 50 different sights for the correct elevation. Thus fire
can be opened far more rapidly and accurately than with rifles, and
can be at once directed on a fresh target without ceasing fire,
while the effect can be seen by the firer, who can instantly change
the rate or cease fire altogether.
The beaten zone is perhaps the most important factor in obtaining
effective fire, and the following table, compiled from _Musketry
Regulations_, 1909, gives the zone beaten by 75 per cent. at four
ranges.
RANGES
------------------+--------------------------------------------------
| Zone containing 75 per cent. of shots
| (effective zone).
+-----------+------------+------------+------------
| 500 yards.|1,000 yards.|1,500 yards.|2,000 yards.
------------------+-----------+------------+------------+------------
Depth | 150 yds. | 70 yds. | 60 yds. | 50 yds.
Lateral Dispersion| 4 ft. | 8 ft. | 13 ft. | 19 ft.
------------------+-----------+------------+------------+------------
It will be seen that the 75 per cent., or effective zone, is
deepest at 500 yards, and gradually decreases as the range
increases up to 2,000 yards; beyond this distance it increases
again in about the same ratio up to 3,000 yards.
The following formula will give the effective zone (75 per cent. of
shots) approximately for all ranges up to 1,500 yards inclusive:
50,000/Range + 20. Example for 1,000 yards: 50,000/1,000 + 20 =
70 yards, which is the depth of the area swept by 75 per cent. of
shots, or the “effective” beaten zone. For ranges beyond 1,500
yards this formula is useless, and after 2,000 the beaten zone
increases in depth, while the angle of descent of the bullets
becomes so steep that the “dangerous space” is reduced to a
minimum; and consequently the zone beaten by 75 per cent. of shots
is no longer the “effective zone,” and it will be necessary to
get the target within the zone beaten by the nucleus, or 50 per
cent. of the shots. This zone at 2,500 yards range is about 50
yards in depth, so an error in estimating the range of more than
25 yards over or under the correct distance will render the fire
“ineffective.” Even at 1,500 yards the “effective zone” (75 per
cent.) is but 60 yards deep, which only allows an error of 30 yards
over or under the correct range--a very small margin, even when
using a range-finding instrument, but without an instrument it is
obviously impossible to “estimate” or “judge” the distance with
sufficient accuracy to ensure bringing the “effective zone” on the
target.
For ranges over 500 yards it is absolutely necessary to know the
range accurately or to find some other method of bringing the
“effective zone” on to the target.
The machine gunner may be likened to the fireman with his
hose-pipe, whose object is to bring the base of his jet of water to
play on a certain spot some distance away from the nozzle of his
pipe. He does not trouble about the distance, he does not require
to know the range; but pointing the nozzle in the direction of the
spot he desires to strike, he elevates or depresses it until he
observes the base of the cone of water falling on the right spot,
and then he holds his pipe so that it continues to fall where he
desires; he does not trouble about the smaller streams and drops of
water that fall short or go beyond, but devotes his whole attention
to keeping the nucleus of the stream--the 75 per cent. or 50 per
cent. zone--falling on his “target.” In precisely the same way the
machine gunner must look upon his stream of bullets as a stream of
water from a hose-pipe, and his object must be to cause the centre
of that stream to play on the target, or, in other words, to bring
the effective cone of fire on the target so that it is the centre
of the beaten zone. This can be done by “observing” the strike of
the nucleus of the shots and altering the elevation accordingly.
On favourable ground fire can be observed by No. 1 up to 800
yards, but No. 2 with the aid of good glasses can observe fire on
favourable ground up to 1,500. This observation of fire is the best
method of obtaining the correct elevation at “effective” ranges
(_i.e._ 1,400 to 600), if the ground is suitable. The procedure
should be as follows: The range should be “estimated” by No. 1, who
should then adjust his sight for 100 or 200 yards less elevation
than the supposed distance, and fire “groups” of 8 or 10 shots; No.
2 observing the strike of the bullets and saying “short” or “over,”
as the case may be, while No. 1 alters the elevation between each
group until No. 2 says “on,” when fire may be continued, still
observed by No. 2, until the desired effect has been attained. No.
1 must be careful to fire his first group of shots short of the
target, as they are much easier to locate than shots which fall
“over.”
If the target is only visible for a short time, the groups may
be “rapid,” but as a rule “deliberate” fire at the quickest rate
should be used, and “rapid” only used when the range has been
found. If the ground is not favourable for the observation of fire,
or the range is too great, this method cannot be used, and it will
be necessary to obtain the range by instruments; but it will not
always be possible to do so, and it is necessary to find some other
reliable way of ensuring that the target is within the “effective”
zone.
Supposing the range to be estimated at 1,400 yards, the effective
zone is about 60 yards in depth--therefore an error of only 30
yards in estimating the range can be permitted. There is but one
way to overcome the difficulty, and that is by _increasing_ the
effective zone; and this can be done by using “combined sights,”
thus making two or more beaten zones which touch each other and
overlap where the effective 75 per cent. of shots of both ends.
There are two ways of using combined sights:
(_a_) The “single gun” method.
(_b_) The “battery” method.
In (_a_), with an estimated range of 1,400 yards, the sights will
be set for 1,300 and aim taken; then the sights will be again
set for 1,500 yards, but without altering the original aim, and
then “rapid” fire opened and the elevating wheel slowly turned to
elevate the gun until the 1,500 yards sighting is aligned on the
target. The result of this operation is to sweep the whole ground
from 1,270 to 1,530 yards with effective fire; and if an error
of 125 yards over or under the correct range has been made, the
target is nevertheless brought within the effective zone by the
combined elevations used. This is the best method for sections or
single guns, and a section can vary this by one gun using 1,250
yards elevation and working up to 1,400, while the other gun begins
at 1,350 and works up to 1,550. The choice of the amount over and
under the estimated range must depend upon the ability of the
person estimating the range and circumstances of the case, but less
than 100 yards over or under should never be used.
The second method (_b_) is only used where at least four guns are
available, and requires six guns to obtain the best results. The
range is estimated as before, and then each gun uses an elevation
differing by 25 yards from the next: thus, taking 1,400 yards again
as an example of the estimated distance, No. 1 gun will use 1,300;
No. 2, 1,325; No. 3, 1,350, and so on, No. 6 using 1,425 yards.
In this way the effective zone of No. 1 gun, which is 60 yards in
depth, will just overlap the effective zone of No. 2 gun, and so
on right up to No. 6 gun. Thus instead of one small zone of 60
yards of effective fire, we have six guns joining to make one big
effective zone 185 yards deep.
Care must be taken not to use more than 25 yards between sights at
ranges over 1,400 yards, otherwise there will be gaps between each
effective zone, and the fire would be ineffective should the target
happen to be at a spot between any two zones.
The methods of firing the gun are laid down in the official
Handbook, but it may be added that in using “deliberate” fire the
double button should be pressed irregularly so as to imitate rifle
fire, and with a little practice a rate of 120 shots a minute can
easily be attained.
This kind of fire, although it should seldom be used, will
occasionally be serviceable in ranging for observation when it
is desired to do away with the peculiar sound of the machine gun
and thus not disclose its presence prematurely. In covering a
retirement it may also be found useful to deceive the enemy into
believing they are only opposed by riflemen, while reserving its
full fire power until a good target presents itself at close range.
“_Continuous_” fire should be used in “gusts” or bursts of from 15
to 30 shots, a momentary pause being made to observe the effect,
and, if necessary, to correct the aim. The great expenditure
of ammunition caused by “continuous” fire renders its use only
justified when the effect obtained is commensurate, and it should
seldom be adopted until the circumstances justify it. But when a
really good target is found at close range, the ammunition need no
longer be considered until there is nothing left alive to fire at.
Annihilation should always be the final aim of machine-gun fire.
TAKING UP A POSITION
Except under special circumstances, such as for covering fire or
a demonstration, the battery will not move as such into position,
but each section will be given its approximate place and move there
independently, keeping touch, however, by signal or connecting
files with the battery commander and acting in close co-operation
with the other sections.
Positions are of two kinds, viz. (1) positions of observation, (2)
positions of readiness.
The position of observation will usually precede the position of
readiness, and the principal points are the concealment of the guns
and detachments, the facilities for observing the enemy and for
movement in any direction.
The position of readiness will be in the immediate vicinity of the
fire positions, and the guns may be actually in position awaiting
the target.
When moving alone on the march, scouts working in pairs must be
pushed well out ahead and on the exposed flank or flanks, and
they should be trained to use a system of signals to indicate the
following: (1) “All clear”; (2) “Enemy in sight”; (3) “A good
target in sight”; (4) “Cavalry” (prepare for); (5) “Artillery
within range”; (6) “A good gun position.”
Six simple and unmistakable signals can easily be arranged and
learned during peace training, which might prove invaluable in
war, for “opportunity” is everything to the machine gunner, and
is usually so fleeting as to demand instant action in order to
obtain success. On moving to occupy a position as a battery, the
guns will usually be in line at from 10 to 100 yards interval, with
the section commanders leading their sections and the scouts well
ahead; the flank guns must arrange for the protection of the flanks
by scouts in the same manner.
[Illustration: DIAGRAM III
TO SHOW FORMATION WHEN COMING INTO POSITION
aaa. The Position. B. Ground Scouts. C. Battery Commander.
D. Connecting files. E. Section Commanders. ee. Flankers.
F. Guns & Detachments.]
The Germans consider that ground scouts should never go into the
proposed position, as they are likely to expose themselves to
the enemy, and thus “give the position away,” and, as already
pointed out, “surprise” is the essence of success. They say that
the commander of the battery or section, whichever the unit may
be, should alone examine the position and select the place for
his battery or section to come into action--and this is the right
method as a general principle; but in broken or hilly country,
where cover is abundant, and where the position is extensive, a
battery commander can do no more than indicate generally the
positions to be occupied by the sections, and it will then be
advisable for the section commanders to personally select the
positions for their guns. If the cover is good, the range-finders
may next occupy the gun positions and proceed to take ranges. They
must be most careful not to show themselves in the least and should
work from cover to cover, some distance from the gun positions
and not on the same alignment. The ranges must be noted on proper
range cards, and when complete sent to the section commanders.
In open country, where there is no good cover in the position,
the scouts will only approach it sufficiently to ensure that it
is not occupied by the enemy, and will then halt and find a good
position for the guns to be dismounted; the commander, passing
through the scouts, will then reconnoitre the position himself,
and select the place for coming into action. There are two methods
of taking up a position, which depend for their choice upon the
proximity of the enemy and the time at which fire is to be opened.
The first is the “deliberate” method, when the guns are brought
up and the range taken before the target appears. In this case
cover is essential to success, and the guns must be most carefully
concealed, the whole object being to surprise the enemy when the
moment arrives, and thus concealment is of the first importance.
The second method is used when the enemy is in the immediate
vicinity, when the country is open and the position without cover,
or when the position is within artillery range of the enemy. The
guns unlimber and prepare for action immediately in rear of the
gun positions, and as close to them as possible and completely out
of sight of the enemy. The commander alone goes into the position,
and having selected approximately where each gun is to go, he
stations them immediately in rear of their intended places out of
sight and then creeps into the position himself and watches for
the opportune moment; when this arrives, a blast on his whistle
brings the guns up with a rush, no concealment is attempted, but,
fully exposed, each gun opens fire on the nearest target. If the
moment has been rightly judged and the range properly estimated,
60 to 90 seconds is sufficient time to obtain the desired effect,
and before the enemy’s artillery can get the range a second signal
from the commander sends the guns out of action again as rapidly
as they appeared. This is one of the most successful methods of
employing machine guns: there is no risk of being seen before the
target appears, there is no “giving away the position” by careless
scouts, and there is no chance that a powerful pair of glasses will
discover the guns in position before they open fire and turn the
tables by surprising them instead. On the other hand, it requires
very highly trained detachments and a vast amount of peace practice
to ensure its success in war.
Alternative positions are always necessary when the deliberate
method is used, and must be carefully practised in peace--the
principal points to be observed being: (1) That the second
position is suitable for bringing effective fire to bear on the
enemy, and (2) that the gun is able to gain the position without
exposure.
Scouts so often forget that they can work with ease where it is
impossible to carry a gun; and unless the above conditions are
fulfilled, the alternative position will be useless.
The place for dismounting the guns must always be as close to the
fire position as possible without exposing the teams to fire or
view; the reserve ammunition must be brought up to this spot, and
precautions must be taken to prevent the teams being surprised
from the flanks or rear if exposed. Machine guns should never be
advanced for a short distance. If it is desired to obtain a closer
range, nothing is gained by moving two or three hundred yards,
while the guns are exposed to considerable risk. The guns are just
as effective at 1,000 yards as at 800, and when a closer range is
necessary they must await the opportunity for moving up to close
range, _i.e._, 300 or 400 yards, where their fire may be decisive.
COVER
Cover may be of two kinds:
(1) _Cover from fire._
(2) _Cover from view._
Cover from fire must be proof against the projectiles likely to be
used against it--that is, against rifle fire and shrapnel. “Cover
from fire” should also be “cover from view” if possible; it must
be inconspicuous, and should be of the same colour and material as
the background and locality. It must be as low as is compatible
with command, and must never be on the skyline. The following
points in the order given constitute good “cover from fire”:
(1) Bullet proof.
(2) Good field of fire.
(3) Invisibility.
(4) Protection from enfilade fire.
(5) Good line of retreat (under cover).
“Cover from view” is often not cover from fire, and must be used
with great caution; it is the principal means by which guns are
brought up to the fire position without the enemy’s knowledge,
thus effecting a surprise. Cover may be either (1) natural, (2)
artificial, (3) a combination of both.
“Cover from fire” will generally be artificial or a combination of
natural and artificial cover, because natural cover will seldom be
found that is suitable for machine guns, although _partial_ cover
from fire may often be found behind a bank, a rock, or in a ditch.
“_Cover from view_” will generally be natural cover, and will be
used to conceal the guns while approaching a position to occupy
it and, when in position, to effect a surprise. When used in
position to effect a surprise, it must be remembered that the
moment the guns open “rapid” fire the cover is no longer any
protection--indeed, it may be a source of great danger should it
be isolated or conspicuous, such as a patch of scrub in a plain,
or a clump of bushes on a hillside, as it will form a mark to aim
at for every gun and rifle within range. “Cover from view” may be
also “cover from fire,” as when folds in the ground or a ravine
are used to conceal the guns. It may also be artificial cover,
such as screens of boughs and brushwood as used by the Japanese
at Liao-yang to conceal their march, or to hide guns in position.
Hurdles covered with grass, reeds, bush, or branches of trees to
closely imitate the surrounding growth, and placed as screens to
hide the guns until the moment arrives for opening fire, will often
prove a most valuable method of concealing guns in position, and
under favourable circumstances the guns may even open fire from
behind the screens without being discovered. This method requires
constant practice in peace to attain success on service--indeed,
the necessity for the most thorough peace training and constant
practice in all the details of bringing guns into action, making
cover, taking up alternative positions, retiring under mutual
support, etc., cannot be too strongly urged on section commanders.
Little ammunition is available for practice in our own service,
it is true, but there is nothing to prevent constant practice in
this vital duty of the machine gunner; and by getting a few men to
represent the enemy, with an intelligent officer and a pair of good
glasses, most valuable help can be given by criticising the manner
the guns are handled, and the amount of exposure or concealment of
the gun and detachment in taking up a position or making cover.
Artificial cover may be either excavated or built up, or a
combination of both. Excavated cover will usually take the form
of a pit of sufficient size to hold the tripod, ammunition, and
three men, and deep enough to conceal the gun and men not only
from view, but from fire at “effective” range. This form of cover
is particularly good on a level plain, the muzzle of the gun being
just above the surface of the ground. The rear side of the pit may
require to be enlarged to take the long leg of the tripod where
time is limited and the pit has not been made large enough to take
the tripod in any position, but it is advisable to make the pit of
sufficient area to allow the gun to be worked in any direction.
With an adjustable tripod, the pit should be so deep that the gun
is completely concealed below the surface of the ground, and it is
only raised when it is intended to open fire.
Other forms of cover consist of epaulements, trenches, sangars,
etc., which will not differ essentially from those given in the
manual of Military Engineering. In all types of “cover from fire”
care must be taken that the cover is high enough to protect No.
1 from bullets fired at ranges up to 1,400 yards, taking into
consideration the angle of descent of the bullets at that range and
the distance of No. 1 from the cover.
Cover can seldom, if ever, combine all the points enumerated here,
and it will lie with the section commander to discriminate between
them and decide what points he will sacrifice in favour of others
more important: thus it may be necessary, where concealment is the
chief object, to forgo “cover from fire” at the longer ranges in
favour of a low parapet or even none at all. It is only possible
to indicate in outline the principles that should be followed;
practice in training and the experience thus gained alone will make
the reader an expert.
Shields will be found of great value in the final stages of the
battle, when machine guns are pushed up to close range to assist
in the final assault. They are too heavy to carry on the guns, and
should be with the ammunition in the first-line transport, where
they are easily obtained if required.
COVERING FIRE
Machine guns will often be used to cover the advance of infantry
from “long” to “effective” range when the artillery is still
occupied in the artillery duel and the infantry first come under
effective rifle fire from the enemy. The ease with which they can
instantly open and cease fire, concentrate on a particular spot, or
sweep a line of trenches, renders them particularly suited for this
purpose, and the Japanese constantly used them to keep down the
enemy’s rifle fire in this manner during the late war.
The narrow beaten zone enables them to fire safely over the heads
of advancing infantry from all ranges beyond 800 yards, provided
the infantry are at least 200 yards from the enemy fired at. A
study of the table of trajectory in the Appendix to _Manual of
Military Training_ will enable the machine gunner to decide the
circumstances under which the fire is safe in each case.
Positions on the flanks and if possible to the front of the
advancing infantry will render covering fire most effective, but
these positions will rarely be possible. The first consideration
is the concealment of the gun from the enemy’s artillery, which
can easily silence them if exposed. It is also necessary that the
positions selected should be sufficiently commanding to enable the
battery commander to see the attacking infantry during the whole
advance, so as to fire only when they are moving, while at the same
time he must be able to see the position of the enemy’s trenches
and thus direct the fire on any part desired.
INDIRECT FIRE
The best method of using covering fire in the early stages of the
attack is by _indirect fire_ from the reverse slopes of a hill
or from behind a ridge or other feature. This is not difficult
to carry out and in no way lessens the accuracy of the fire or
endangers the troops in front, as the following experiment will
prove.
EXPERIMENT IN INDIRECT FIRE
The following is an extract from an article by First Lieutenant A.
E. Phillips of the 10th Cavalry, from the _Journal_ of the United
States Cavalry Association for July 1909:
“To determine how many, if any, of the bullets from the machine gun
would strike troops in front of an assumed ‘hill’ over which the
gun was to fire, canvas frames were used to represent such objects,
the targets being concealed from view.
“The target consisted of a strip of target cloth 6 ft. high and
15 yards wide, along the bottom edge of which is pasted a row of
kneeling figures with an interval of a yard from centre to centre.
Across the target and parallel to its top edge was drawn a narrow
black line tangent to the tops of the heads of the figures. Value
of hits on any figure = 5; value of hits on the cloth below the
line = 3; value of hits on the cloth above the line = 1. Canvas
frame, 8 ft. high, placed 200 yards in front of the gun. Rapid fire:
_First Experiment_
Range 800 yards
-------+-------------------------------+-----------------------------
| No. of Hits. |
No. of +------+-------+-------+--------+ Remarks.
shots. | Figs.| 5’s. | 3’s. | Total. |
-------+------+-------+-------+--------+-----------------------------
| | | | |
30 | 5 | 10 | 12 | 22 | Line of sight was 5 ft.
30 | 8 | 10 | 9 | 19 | below top of obstruction.
| | | | | All shots over.
-------+------+-------+-------+--------+-----------------------------
_Second Experiment_
Range 1,000 yards
-------+----------------------------------+---------------------------
| No. of Hits. |
No. of +------+-----+-----+---------------+
shots. | Figs.| 5’s.| 3’s.|Total per cent.| Remarks.
| | | | of figs. hit. |
-------+------|-----|-----|---------------+---------------------------
| | | | |
30 | 9 | 11 | 4 | 60 | Line of sight was 3 ft.
30 | 12 | 17 | 7 | 80 | below top of obstruction.
| | | | | All shots over.
-------+------+-----+-----+---------------+---------------------------
_Third Experiment_
Range 1,200 yards
-------+----------------------------------+---------------------------
| No. of Hits. |
No. of +------+-----+-----+---------------+
shots. | Figs.| 5’s.| 3’s.|Total per cent.| Remarks.
| | | | of figs. hit. |
-------+------|-----|-----|---------------+---------------------------
30 | 2 | 2 | 5 | 13 | Line of sight was 3 ft.
30 | 4 | 5 | 13 | 27 | below top of obstruction.
0 | 8 | 11 | 9 | 53 | All shots over.
-------+------+-----+-----+---------------+---------------------------
“It will be noticed no 1’s were made. Assuming the height above
the ground of the average mounted soldier as 8 ft., had a troop
of cavalry mounted been 200 yards in front of the machine guns
in the third experiment, the line of sight would have struck
about the backs of their horses, and all bullets would have gone
over the riders with at least 4 feet to spare, as proved by the
experiment.... The troop mounted could have moved forward to within
100 yards of the target and would not have been struck by the
bullets.”
The methods of carrying out indirect covering fire will vary
according to the nature of the position selected and the way the
guns are to be laid. This is one of the few occasions when a
battery or two may have all their guns in line close together. If
the slope is a steep one, they may be pushed up close to the crest,
but on a gentle slope they must be placed sufficiently far back to
avoid the forward effect of shrapnel bursting on the crest line.
The battery commander will select the position for the guns and
will then give each gun or section a section of front to fire on.
The method of marking off this section is as follows: two iron rods
about 3 ft. long for each gun are painted white, and are then “laid
off” from the gun to the target, in an exact line, the first being
on the reverse slope a few yards short of the crest; the next on or
just behind the crest line. By aligning the gun on the rods, fire
is brought on the centre of the target; should traversing fire be
required, the limits may be marked by similar sticks on either side.
There are two methods of laying the gun. (1) By observation of
fire. (2) By quadrant elevation. The first method has been already
described, and the second must be done by using the following
table in conjunction with an instrument for elevating the gun at
the required angle; but it must be remembered that each gun will
require adjusting to its own angle of elevation to suit its known
error at each range. Thus a gun which is known to require sighting
at 900 yards when firing at 1,000 should receive 1° 10½ and not 1°
25½. When proper instruments are not obtainable, very fair results
may be obtained by using an ordinary clinometer. The necessary
allowance for the height the gun is above the target must be made,
or, in other words, the angle of sight as shown by the clinometer
must be deducted from the quadrant elevation given on the gun.
[Illustration: DIAGRAM IV
TO SHOW METHOD OF LAYING BY AIMING POSTS
aa. Aiming Posts (about 15^x apart and some distance in front
of gun.)
ttt. Targets.]
TABLE OF ELEVATION FOR MAXIM ·303 USING AMMUNITION GIVING 2,000 F.S.
------------+---------------------------
Range. | Angles of elevation on the
| Maxim gun.
------------+---------------------------
200 yards | 0 4·0 0 1
300 ” | 0 9·5 ”
400 ” | 0 17·0 ”
500 ” | 0 25·5 ”
600 ” | 0 35·5 ”
700 ” | 0 45·5 ”
800 ” | 0 57·5 ”
900 ” | 1 10·5 ”
1,000 ” | 1 25·5 ”
1,100 ” | 1 41·5 ”
1,200 ” | 1 57·5 ”
1,300 ” | 2 16·5 ”
1,400 ” | 2 37·5 ”
1,500 ” | 2 59·5 ”
1,600 ” | 3 22·5 ”
1,700 ” | 3 47·5 ”
1,800 ” | 4 14·5 ”
1,900 ” | 4 43·5 ”
2,000 ” | 5 14·5 ”
2,100 ” | 5 42·0 ”
2,200 ” | 6 22·0 ”
2,300 ” | 6 59·0 ”
2,400 ” | 7 40·0 ”
2,500 ” | 8 25·0 ”
2,600 ” | 9 16·0 ”
2,700 ” | 10 18·0 ”
2,800 ” | 11 18·0 ”
------------+---------------------------
What is required is the angle of _quadrant elevation_ to be put on
the gun in order that the shots may strike the target at a known
range. From range table obtain _angle of tangent elevation_; now
if the target is _below_ the guns we must _subtract_ the angle of
sight (_m_), if the target is _above_ the guns we must _add_ the
angle of sight (_m_) to obtain correct angle of quadrant elevation.
_To obtain angle of sight m_
(1) When target is visible from the immediate vicinity of guns the
angle may be measured by pocket clinometer or other mechanical
means; or, if heights can be obtained from a contoured map, from
the formula:
_m_ = (_h_ × 1146)/R
where _h_ = difference in _feet_ of height between guns and target;
R = range in yards.
(2) When target is not visible from immediate vicinity of guns, _m_
may be found from the following formula:
[Illustration: DIAGRAM V
(a_{1} × OG + a_{2} × OT)/GT
Where a_{1} is the angle of sight from O to G; a_{2} is the angle
of sight from O to T.]
Angles of elevation are read plus, angles of depression minus; T
being the target, G the gun, and O the observer.
Before firing it is necessary to ascertain that the trajectory will
clear the intervening crest--_i.e._ see that the angle of slope to
the top of crest is less than the angle of Q.E. at which the gun is
likely to be fired. If there is an obstacle some distance in front
of the guns, to ascertain if the trajectory will clear it make a
liberal estimate of the range to the obstacle and ascertain if the
quadrant elevation to be fired at is greater than that which would
be required to hit the obstacle.
If it is possible to place a mark to aim at near the crest with a
given elevation which will ensure the fire striking the target,
this will much simplify indirect fire, but the combination of
circumstances required to enable this to be done will not often be
found.
When all is ready to open fire the battery commander will take up a
position from which to direct it, and will give the orders to open
and cease fire and name the guns or sections to fire. The section
commanders will watch the fire effect of their guns and give the
orders necessary for correcting elevation or direction. The battery
captain will assist the commanding officer by noting the fire
effect.
It will be seen from the foregoing that considerable practice is
required to enable indirect fire to be efficiently carried out; but
the results obtained in covering the advance of infantry and thus
enabling them to push up quickly to close range, without the delay
and exhaustion caused by a prolonged fire fight, will more than
repay the time spent in perfecting machine-gun detachments in this
duty.
SUMMARY OF GENERAL PRINCIPLES
_With Cavalry._--To enable it to retain its mobility and do away
with the necessity of dismounting whole squadrons for fire action.
To give it greater power both in attack and defence, and enable
small detachments to hold important strategical or tactical points.
To act as escort to artillery and to assist in the pursuit.
_With Infantry._--To cover the first advance with fire. In attack
they should be held back until the last reserve has been thrown in,
when they must be used to bring an overwhelming fire to bear on
the point selected for assault. Owing to their narrow beaten zone
and great accuracy, they can safely fire over the heads of prone
infantry within 100 yards of the position. A Japanese officer who
commanded a machine-gun battery at the battle of Mukden said on one
occasion he “continued this fire until their attacking infantry
were within 30 metres of the enemy’s position.”[6]
They may also be used to reinforce threatened points, when their
mobility will enable them to arrive at a distant part of the
battlefield with the rapidity of cavalry. They should rarely be
used in the firing line, where their fire, being dispersed, is less
effective than an equal volume of rifle fire, and where they are
at once the target for every rifle. Machine guns can never engage
artillery, and should avoid engaging other machine guns or firing
on a line of skirmishers.
They are particularly useful at night with the outposts, and can be
trained by day on roads, defiles, or bridges, and thus can be used
in the dark to sweep the approaches with accurate fire.
The Golden Rule for Machine Gun Tactics may be thus expressed:
“Conceal your guns, utilise cover, and operate by surprise--for
surprise is the essence of tactical success.”