26. General Characteristics of Field Artillery Action.—The duty of field artillery in action is to fire with the greatest effect on the target which is for the moment of the greatest tactical importance. This definition of field artillery tactics brings the student at once to questions of combined tactics, for which consult the article [Tactics]. The purpose of the present article is to indicate the methods employed by the gunners to give effect to their fire at the targets mentioned. For this purpose the artillery has at its disposal two types of projectile, common (or rather, high explosive) shell and shrapnel, and two fuzes, “time” and “percussion” (see [Ammunition]). The actual process of coming into action may be described in a few words. The gun is, at or near its position in action, “unlimbered” and the gun limber and team sent back under cover. Ammunition for the gun is first taken from the wagon that accompanies it, as it is very desirable to keep the limbers full as long as possible, in case of emergencies such as that of a temporary separation from the wagon. Limber supply is, however, allowed in certain circumstances. The wagon is now placed as a rule by the side of the gun, an arrangement which immensely simplifies the supply of ammunition, this being done under cover of the armour on the wagon and of the gun-shield and also without fatigue to the men. The older method of placing the wagon at some distance behind the gun is still occasionally used, especially in the case of unshielded equipments. No horses are allowed, in any case, to be actually with the line of guns. According to the British Field Artillery Training of 1906, a battery in action would be thus distributed: first, the “fighting battery” consisting of the six guns, each with its wagon alongside, and the limbers of the two flank guns; then, under cover in rear, the “first line of wagons” comprising the teams of the fighting battery, the four remaining gun limbers, and six more wagons. The non-combatant vehicles form the “second line of wagons.”
27. Occupation of a Position.—This depends primarily upon considerations of tactics, for the accurate co-operation of the guns is the first essential to success in the general task. In details, however, the choice of position varies to some extent with the nature of the equipment: for instance, an elevated position is better adapted than a low one for high velocity guns firing over the heads of their own infantry, and again, the “spade” with which nearly all equipments are furnished (see [Ordnance]) should have soil in which it can find a hold. Cover for the gun and its detachment cannot well be obtained from the configuration of the ground, because, if the gun can shoot over the covering mass of earth, the hostile shells can of course do likewise. Sufficient protection is given by the shield, and thus “cover” for field-guns simply means concealment. Cover for the “first line of wagons” is, however, a very serious consideration. As to concealment, it is stated that “the broad white flash from a gun firing smokeless powder is visible” to an enemy “unless the muzzle is at least 10 ft. below the covering crest” (Bethell, Modern Guns and Gunnery, 1907, p. 147). Concealment therefore, means only the skilful use of ground in such a way as to make the enemy’s ranging difficult. This frequently involves the use of retired positions, on reverse slopes, in low ground, &c., and in all modern artillery the greatest stress is laid on practice in firing by indirect means. Controversy has, however, arisen as to whether inability to see the foreground is not a drawback so serious that direct fire from a crest position, in spite of its exposure, must be taken as the normal method. The latter is of course immensely facilitated by the introduction of the shield. A great advantage of retired positions is that, provided unity of direction is kept, an overwhelming artillery surprise (see F. A. Training, 1906, p. 225) is carried out more easily than from a visible position. The extent of front of a battery in action is governed by the rule that no two gun detachments should be exposed to being hit by the bullets of one shell, and also by the necessity of having as many guns as possible at work. These two conditions are met by the adoption of a 20-yards interval between the muzzles of the guns. At the present time the gun and its wagon are placed as close together as possible, to obtain the full advantage of the armoured equipment. The shield, behind which the detachments remain at all times covered from rifle (except at very short range) and shrapnel bullets,[3] enables the artillery commander to handle his batteries far more boldly than formerly was the case. General Langlois says “the shield-protected carriage is the corollary to the quick-firing gun.” Armour on the wagon, enabling ammunition supply as well as the service of the gun, to be carried on under cover, soon followed the introduction of the shield. The disadvantage of extra weight and consequently increased difficulty of “man-handling” the equipment is held to be of far less importance than the advantages obtained by the use of armour.
28. Laying.—“Elevation” may be defined as the vertical inclination of the gun, “direction” as the horizontal inclination to the right or left, necessary to direct the path of the projectile to the object aimed at. “Laying” the gun, in the case of most modern equipments, is divided, by means of the device called the independent line of sight (see [Ordnance]), into two processes, performed simultaneously by different men, the adjustment of the sights and that of the gun. The first is the act of finding the “line of sight,” or line joining the sights and the point aimed at; for this the equipment has to be “traversed” right or left so as to point in the proper direction, and also adjusted in the vertical plane. The simplest form of laying for direction, or “line,” is called the “direct” method. If the point aimed at is the target, and it can be seen by the layer, he has merely to look over the “open” sights. But the point aimed at is rarely the target itself. In war, the target, even if visible, is often indistinct, and in this case, as also when the guns are under cover or engaging a target under cover, an “aiming point” or “auxiliary mark,” a conspicuous point quite apart and distinct from the target, has to be employed (“indirect” method). In the Russo-Japanese War the sun was sometimes used as an aiming point. When the guns are behind cover and the foreground cannot be seen, an artificial aiming point is often made by placing a line of “aiming posts” in the ground. If an aiming point can be found which is in line with the target, as would be the case when aiming posts are laid out, the laying is simple, but it is as often as not out of the line. Finding the “line” in this case involves the calculation, from a distant observing point, of the angle at which the guns must be laid in order that, when the sights are directed upon the aiming point, the shell will strike the target. It is further necessary to find the “angle of sight” or inclination of the line of sight to the horizontal plane. If aim be taken over the open sights at the target, the line of sight naturally passes through the target, but in any other case it may be above or below it. Then the point where the projectile will meet the line of sight, which should coincide with the target, is beyond it if the line of sight is below or angle of sight is too small, and short of it if the line of sight is too high—that is, range and fuze will be wrong. The process of indirect laying for elevation therefore is, first, the measurement of the angle of sight, and secondly, the setting of the sights to that angle by means of a clinometer; this is called clinometer laying. In all cases the actual elevation of the gun to enable the shell to strike the target is a purely mechanical adjustment, performed independently; the gun is moved relatively to the sights, which have been previously set as described. Frequently the battery commander directs the guns from a point at some distance, communication being maintained by signallers or by field telephone. This is the normal procedure when the guns are firing from cover. Instruments of precision and careful calculations are, of course, required to fight a battery in this manner, many allowances having to be made for the differences in height, distance and angle between the position of the battery commander and that of the guns.
29. Ranging[4] (except on the French system alluded to below) is, first, finding the range (i.e. elevation required), and secondly, correcting the standard length of fuze for that range in accordance with the circumstances of each case. To find the elevation required, it is necessary to observe the bursts of shells “on graze” with reference to the target. The battery commander orders two elevations differing by 300 yds., e.g. “2500, 2800,” and tells off a “ranging section” of two guns. These proceed to fire percussion shrapnel at the two different elevations, in order to obtain bursts “over” (+) and “short” (−). When it is certain that this “long bracket” is obtained, the “100 yds. bracket” is found, the elevations in the given case being, perhaps, 2600 and 2700 yds. “Verifying” rounds are then fired, to make certain of the 100 yds. bracket. The old “short bracket” (50 yds.) is not now required except at standing targets. Circumstances may, of course, shorten the process; for instance, a hit upon the target itself could be “verified” at once. The determination of the fuze (by time shrapnel) follows. The fuze has a standard length for the ascertained range, but the proper correction of this standard length to suit the atmospheric conditions has to be made. The commander has therefore already given out a series of corrector[5] lengths, his object being to secure bursts both in air and on graze. When he is finally satisfied he opens fire “for effect.”
30. An example of the ordinary method of ranging, adapted from Field Artillery Training, 1906, is given below.
Battery commander gives target, &c., and orders: “Right section ranging section; remainder corrector 150 increase 10, 4400-4700,” for the long bracket.
No. 1 gun fires, elevation 4400 yds., P.S., round observed −
No. 2 gun fires, elevation 4700 yds., P.S., round observed +
B.C. orders “4500-4600.”
No. 1 gun fires, elevation 4500 yds., P.S., round observed −
No. 2 gun fires, elevation 4600 yds., P.S., round observed +
The 100 yds. bracket appears to be 4500-4600. B.C. orders: “Remainder 4500 time shrapnel,” and gives the ranging section 4500-4600 to “verify.” Guns 3, 4, 5, 6 set fuzes for 4500 with correctors 150, 160, 170, 180.