CHAPTER IIGENERAL 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 fromField 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 descriptionsurpriseis 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—suitabletargetat closerangefrom a concealedposition.
Napoleon’s maxim, that “fire is everything—the rest is of small account,” is only applicable to the machine gun when the fire iseffective. 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 tothe 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 fromMusketry Regulations, 1909, gives the zone beaten by 75 per cent. at four ranges.
RANGES
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:50,000Range+ 20.Example for 1,000 yards:50,0001,000+ 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 withsufficient 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 theaid 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 inestimating the range can be permitted. There is but one way to overcome the difficulty, and that is byincreasingthe 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 of125yards 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 atleast 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 founduseful 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.
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 anddetachments, 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.
Diagram IIITO SHOW FORMATION WHEN COMING INTO POSITIONaaa. The Position. B. Ground Scouts. C. Battery Commander. D. Connecting files.E. Section Commanders. ee. Flankers. F. Guns & Detachments.
Diagram IIITO 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.
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 commanderof 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 thepositions 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 iswithin 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 principalpoints 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 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 fromfire” 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, althoughpartialcover 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 dangershould 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 amountof 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.
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 toManual of Military Trainingwill 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.
The best method of using covering fire in the early stages of the attack is byindirect firefrom 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.
The following is an extract from an article by First Lieutenant A. E. Phillips of the 10th Cavalry, from theJournalof 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
Second Experiment
Range 1,000 yards
Third Experiment
Range 1,200 yards
“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 sightingat 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.
Diagram IVTO SHOW METHOD OF LAYING BY AIMING POSTSaa. Aiming Posts (about 15xapart and some distance in front of gun.)ttt. Targets.
Diagram IVTO SHOW METHOD OF LAYING BY AIMING POSTS
aa. Aiming Posts (about 15xapart and some distance in front of gun.)ttt. Targets.
aa. Aiming Posts (about 15xapart and some distance in front of gun.)
ttt. Targets.
TABLE OF ELEVATION FOR MAXIM ·303 USING AMMUNITION GIVING 2,000 F.S.
What is required is the angle ofquadrant elevationto be put on the gun in order that the shots may strike the target at a known range. From range table obtainangle of tangent elevation; now if the target isbelowthe guns we mustsubtractthe angle of sight (m), if the target isabovethe guns we mustaddthe 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 bypocket clinometer or other mechanical means; or, if heights can be obtained from a contoured map, from the formula:
m=h× 1146R
whereh= difference infeetof height between guns and target; R = range in yards.
(2) When target is not visible from immediate vicinity of guns,mmay be found from the following formula:
Diagram Va1× OG + a2× OTGTWhere a1is the angle of sight fromO to G; a2is the angle of sight from O to T.
Diagram V
Where a1is the angle of sight fromO to G; a2is 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 estimateof 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.
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 thedark 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.”