Machine guns will never be able to replace artillery at long ranges; on the other hand, they will often find an opportunity to support other arms with their fire at medium and short ranges. It has been asserted that machine guns do not always follow the movements of the firing lines in action, that the commander of a force is not always able to find a good position for them; and the question raised whether the space taken up by the machine guns and their ammunition wagons in a column could not be more profitably filled by companies of infantry or by a portion of an ammunition column of corresponding length. To be sure, machine guns are a special arm; the justification of their existence lies in the combination of constant readiness for firing with highly developed mobility, so that, held back under direct control of the commander of a force, they give him the means wherewith to produce within a short time a sudden effect, in the nature of a surprise. This is the very purpose for which machine guns were created. They are not intended for prolonged fire action, not for accompanying an infantry skirmish line in an advance by rushes, and, least of all, for fighting well covered firing lines. In addition, the fact that machine guns make it possible to concentrate fire quickly on any space, whereby the moral effect is considerably increased, ought not to be underestimated. It would seem to be advisable to employ machine guns in conjunction with infantry when it is impossible to develop a powerful fire on account of the conformation of the ground, but when such fire is desirable for commanding approaches or defiles; further, when fire alone suffices for delaying the enemy (for example, in rear guard actions). In this case the guns may either be pushed far to the front, or may be used in defensive positions, which can then be held by a few men during the pauses in the fight.[297] Although machine gun fire may perhaps be relatively less accurate than that of a body of infantry, the value of pouring a large mass of projectiles on the enemy within a brief space of time should not be underestimated.[298] [297] At the Austrian Musketry School it was found that it was not easy for a body of troops to fire on targets illuminated by the shaft of a search light; few men possessed the requisite eyesight to make this possible. It would no doubt be practicable, however, to attach such men to the machine guns posted in a defensive position. A considerable increase in fire effect could thus be obtained. [298] Platoon volleys, directed for one minute on figures advancing from 1200-1100 paces, resulted in 5, fire at will, in 1¹⁄₂, and machine gun fire, in 3% hits. The three kinds of fire, when directed against 30 prone skirmishers, resulted, in one minute, in 13, 18, and 10% hits, respectively.