The infantry carriages are heavy, clumsy, and conspicuous, and are the least mobile of all; they can hardly be moved out of a walk without risk, and Marks III. and IV. cannot come into action without first unharnessing the mule or horse, and they then have to be dragged into position by the whole detachment—thus presenting a most conspicuous and vulnerable target at the moment when least desired and when concealment and invisibility are essential to tactical success.[4] In the German Official Account of the late Boer War, issued by the General Staff, is the following criticism of this carriage:
“Both sides have machine guns, but the rather clumsy mountings of those used by the British offered too high a target, and so prevented their being advanced from position to position during the attack.”
The tripod mounting, which is light and inconspicuous, is carried with the gun on a limbered wagon; but the advantages of its lightness and portability are almost neutralised by being carried on a wagon, thus reducing its mobility by confining it to ground suitable for wheeled vehicles.
If used on a pack-saddle the difficulty of managing a led animal on foot in the stress of battle may become insuperable, and moving the gun in and out of action is entirely dependent on the docility of the pack-animal. The gun weighs anything from 40 to 60 lb., while the mountings need not weigh more than 34 lb. The combined weight of a gun and mounting should never exceed 120 lb. and can be as little as 74 lb.
In whatever way it is decided to carry the gun, it is a sine quâ non that it must be at least as mobile as horse artillery. There is no reason why it should not be as mobile as cavalry, and the choice remains between a pack-horse with a mounted detachment or a galloping carriage; and the former is in every way preferable, principally because it can carry the gun and ammunition across any country, and can come into action in less than 30 seconds on an adjustable tripod, which can be carried by hand into any position and presents a very small, inconspicuous target.
The majority of foreign countries have adopted pack transport for their machine guns. It is desirable with infantry and absolutely essential with cavalry. A suitable saddle is, of course, indispensable, and strong spiral springs to the hooks which hold the gun and tripod on either side will entirely prevent horses from straining their backs when galloping across country or jumping obstacles with the guns. These hooks must be leather-covered and made to fit the gun exactly, and, in order to do away with the present cumbersome straps and buckles, they should have a hinged attachment to close over the gun and lock automatically in such a way as to admit of its being opened by a single movement when it is required to dismount the gun. The Swiss and the Americans have permanently adopted pack transport for the machine guns with their cavalry, which are able to accompany them over any country without detriment to either horses or guns; and in the American army the average time for a well-trained cavalry machine-gun detachment to go into action front, from mounted formation, unpack, and set up the guns, load, aim, and open fire, is 25 seconds; while at the departmental meeting for 1908 the machine guns of the 10th Cavalry, from the halt in line, moved forward in section column at a gallop for 200 yards and went into action and fired a blank shot in 31 seconds.[5]
This brings us to the second factor—Visibility. It is absolutely necessary for the successful tactical employment of machine guns that they should be as inconspicuous as possible when in action; the gun itself is a very small object when close to the ground, and its visibility will depend almost entirely on the nature of mounting and its adaptability for use behind cover of varying heights. All our infantry carriages are so conspicuous as to be quite unconcealable except in defence, the wheels being 4 ft. 8 in. in diameter and the gun axis 3 ft. 6 in. above the ground. The Mark IV. tripod is the handiest and least conspicuous of the mountings at present in use in our service, and although it weighs 48 lb. it can be carried into almost any position and easily concealed. It can be adjusted to fire at any desired height between 14½ and 30 in. above the ground level, and consequently can be used from behind any suitable cover.
Vulnerability.—The question of vulnerability would appear at first to depend entirely on visibility; or, in other words, on the target presented to the enemy’s fire, but this is only true to a certain extent. To obtain the minimum vulnerability it is of course necessary to have the gun as low and inconspicuous as possible, because the less it can be seen and the better cover it can obtain, the more difficult it will be to locate and hit. But the true vulnerability of the gun in comparison with infantry lies in the amount of front they occupy respectively; or in other words, the breadth of the target exposed to the enemy and the percentage of loss they can each sustain without their fire effect being reduced. Infantry will never again fight in two ranks in civilised warfare, and the closest formation possible for a firing line is one pace per man; 50 men will therefore occupy a front of, roughly, 50 yards; in other words, the target presented to the enemy is 50 yards in breadth, and, provided the elevation is correct, shots striking anywhere within this 50 yards will be effective. The machine gun, however, only occupies a front of from 4 ft. to 5 ft. 2 in., or 1/25th the front offered by infantry having equal fire effect. It is on this point that the wonderful tactical possibilities of the machine gun rests: the maximum of rifle fire from the minimum of front. It is obvious that 10 per cent. of casualties in the infantry firing line reduce the fire effect by just that amount, while from 30 to 40 per cent. will probably silence its fire altogether or render it ineffective. The machine gun, on the other hand, is unaffected by even 50 per cent. of loss, while it can suffer 80 per cent. of loss without diminishing its fire effect, though such a loss would of course cause it to lose its mobility and seriously affect the morale of the gunners. A machine-gun detachment consists of from 16 to 24 men, but only two of them actually work the gun, and one man alone can fire the gun once it is in action, the second man merely assisting him with the ammunition, etc., but he is not absolutely necessary to the firing of the gun. Thus we see that the killing of the gunner only causes a momentary cessation of fire until another man takes his place, when the fire is resumed without loss of intensity, accuracy, or concentration.
We are now in a position to form an accurate estimate of the potentialities of the machine gun and its true tactical value as compared with infantry, and we find: