Translated by LIEUT. (jr. grade) C. C. GILL, U. S. Navy
A. F. WESTCOTT, PH. D., Instructor, U. S. Naval Academy
TRANSLATORS' NOTE.—This analysis, prepared by a well-known Italian naval tactician and appearing in the official organ of the Italian General Staff, may be taken as the product of experience gained in the recent trouble with Turkey, combined with the careful study and original research for which the Italian Navy is distinguished.
Whatever its intrinsic value, it merits the attention of naval officers as an example of the way in which the Italian General Staff indoctrinates its personnel with the underlying reasons for the adoption of a definite plan of fleet organization and training. While it is not a mere mathematical trick demonstration, nor yet a speculation on long accepted general principles, the article is noteworthy for its mathematical precision, logical sequence, and conformity to accepted theories in dealing with a very practical question.
The hypotheses demonstrated are:
1. The most efficient concentrating group is two ships.
2. The division should consist of two concentrating sections, and should ordinarily maintain the conventional column formation.
3. A squadron should consist of two or at most three divisions operating individually but with unity of control and unity of action. (A larger number of ships should form two squadrons maneuvering independently but coordinately.)
The elemental subdivision (reparto elementare) of a naval force may be taken as that number of ships which are primarily designed to fire at the same target. For example, this elemental subdivision, or concentrating group, will consist of one ship if each ship fires at a separate target; or of two, three, or four ships, if groups of such respective numerical values concentrate their fire.
The first question to be considered is: What is the proper numerical strength of this elemental subdivision? Or, in other words, how should a fleet be divided into concentrating groups in order to secure maximum effectiveness of gun-fire?
The motive for concentration is based on the axiomatic principle that gun-fire should be so controlled as to secure a decisive advantage in the minimum time.
At first glance, it might be supposed that the effectiveness of fire would increase in proportion to the size of the concentrating groups; for it seems plausible that the larger the concentrating groups, the more quickly would their attack produce tangible results. One might infer, therefore, that in the case of two opposing forces, consisting of an equal number of ships similar in type and equal in unit offensive power, the one with the larger concentrating groups would the more readily destroy the balance of numerical equality, thus securing both material and moral advantage.
But increasing the number of ships in the concentrating groups necessarily decreases the number of target ships, and thus leaves a larger number of enemy ships free to fire undisturbed by hostile attack. This point is important, for the effectiveness of a ship's attack varies inversely with the effectiveness of the attack to which it is exposed. This compels attention to the fact that if a concentrating group of a given strength is sufficient to get decisive results in a relatively short time, then a larger concentrating group would be a wretched tactical disposition of forces.
Here it may be noted that in past years, when engagements at long range first came into general discussion, it was entirely logical that the concentrating group should be made up of a fairly large number of ships; in fact, since the pre-dreadnoughts carried relatively few heavy guns, it was not reasonable to expect that the initial advantage could be gained at fairly long ranges, unless a considerable number of ships concentrated their fire. The adoption of this practice was thus a tactical necessity, even though the numerical increase of the concentrating group involved a marked decrease in firing efficiency (i. e., in the percentage of hits made by individual ships).
But with the evolution of battleship design, unit offensive power has increased enormously, though without a corresponding increase in ability to withstand attack. In truth, despite increased strength of armor, the battleship remains a colossus with feet of clay, particularly in view of the ease with which its offensive power may be compromised. For example, a ship whose fire-control system suffers a casualty is for the time being powerless, and if the enemy succeeds in maintaining a concentrated fire, the advantage so gained may become quickly decisive. Taking into account, therefore, that the latest type of battleship possesses by its very construction a great concentrating power, we may, on the basis of the points already established, set forth the principle that it is neither necessary nor advisable to increase the numerical size of the concentrating group beyond the point where effectiveness of gun-fire suffers diminution. In other words, the elemental subdivision may consist of three ships if, in concentrating the fire of such a subdivision, all the ships are able to get the same number of hits as, in a given time, they could secure firing independently; otherwise it is advisable to limit the size of this elemental subdivision to two ships.
Stated in these terms, the issue evidently turns on the fire control. In order that all ships when concentrating may get as many hits as when firing independently, there are two essential conditions:
1. Rapidity of fire should not be reduced; i. e., each ship should fire as rapidly when concentrating as when firing independently.
2. Accuracy of fire should not be reduced; i. e., in order that the spotters may identify their respective salvos, the fire of two or more concentrating ships should not be superimposed.
The first condition is evident; the second may be made clear by the following explanation:
Let us first consider the method by which the ships of the group concentrate while firing simultaneously. In order to apply this method under the most favorable conditions, it is necessary for each ship to spot the ranging shots independently—either by letting the ships fire one after another at the same target, or by firing simultaneously at contiguous targets and getting thereby the necessary data for calculating the sight-bar ranges to the concentration target. For the concentration, when the various ships open fire simultaneously on the same target, then the hits of each ship will be bunched. Now, from the observation of these results, it is necessary for the spotters to control the combined salvos as if they were all fired from one ship. But in doing so, no matter how well the ranges have been corrected, and no matter how well the initial salvos have been bunched, there will inevitably follow an increasing dispersion in the fall of shells. To verify this, it will be sufficient to consider the following instance. The hits of one ship may be short, while those of another are over. It will be necessary for the spotter of each ship to shift the center of impact of his own salvo; but if the combined salvos appear centered on the target, how is the fire susceptible of improvement? Generally speaking, indeed, this method can give only a small percentage of hits; for example, in recent French target practice, it was shown that when two ships concentrated firing simultaneously (i. e., at the same interval), the number of hits was scarcely greater than when one ship fired alone.
It might be supposed that when two ships fire at the same target, each could distinguish the points of fall of her projectiles by the different locations in the plane of fire. But this is not true; it is impossible to avoid confusion, especially in the case of two adjoining ships. Thus, in Fig. 1, we have two ships A1 and A2, which are separated from each other by a distance d and which are concentrating on the target B, range x; let us assume, for a definite case, that P1 and P2 are projectiles falling over by a distance s=BP1=BP2. The distance P1P2 between the splashes is determined by the formula
Let d=500 m.; x=8000 m.; S=300 m.; the value of P1P2 is less than 20 meters. This distance is so small that it would be impossible to tell whether the shell P1 came from the ship A, or whether it was fired from A2, somewhat wild laterally.
It is necessary therefore to recognize that, in order to maintain accuracy, the concentration ships should fire not simultaneously but successively; each ship should be autonomous, except that all should observe the prescribed interval between successive salvos to avoid confusion in their identification.
From this it follows that the maximum number of ships that may take part in concentration is given by the formula T/t, T being the interval between successive salvos from the same ship, and t the interval between the successive salvos from the concentrating group (fired of course by different ships).
At first glance, it might appear that the value of t could be reduced to a very few seconds; but as a matter of fact, if t is not given a fairly large value, the method will not accomplish its purpose, i. e., the effectiveness of the fire will be diminished. The proof of this may be derived in the following way.
As has been said, it is neither possible nor desirable for each ship to maintain a firing interval with absolute exactness. After a salvo is fired, data are obtained and a sight-bar range is predicted for firing the next salvo. Upon the assumption that the change in range during the prescribed salvo interval remains constant, the necessary range correction is of course combined with the spotter's corrections if the salvo is not apparently centered. Now if the latest range-finder reading indicates that the range predicted for the next salvo will be reached a little before the expiration of the regular interval T, the salvo, if it is ready, will be fired a little ahead of time. Analogously, it will be fired a little after the regular interval, if the range predicted is reached after the interval T.
It will now be conceded that, while the first salvo will be fired at exactly the interval t after the ship preceding, the later salvos will not be fired at precisely this interval, or at least damaging complications are sure to result if the interval is strictly maintained. However, as has been pointed out, the interval is prescribed merely as a guide and not as an ironclad restriction. And aside from all this, the shots of a salvo are not in any case all fired at the same instant, but within a leeway of a few seconds, so that the interval inevitably suffers some variation.
It is evident from these considerations that if the interval t between the salvos of two ships firing successively, is made too short, then by the little that one lags and the other advances, the shots after a few salvos will be confused, and thus the effectiveness of the fire diminished.
The firing, therefore, should be begun with a sufficient interval between the salvos of successive ships to allow for the abovementioned variation. If this is done, the fire can be controlled with the greatest freedom; each ship has only itself to think of—that is to say, may conduct its fire as if it were alone; and the shots will never be confused.
We are forced then to conclude that in order to avoid the disadvantage of having the percentage of hits greatly reduced, the interval t must be assigned a value of from 15 to 20 seconds. Now, taking into consideration the value that must be given to T, the number of ships that may properly take part in concentration, that is T/t , is equal to two. If we wish to concentrate the fire of a larger number of ships, giving the initial interval t the value indicated, each ship cannot develop the maximum rapidity of fire. It may be repeated, then, that the most suitable numerical strength for the elemental subdivision or concentrating group consists of a section of two ships.
It may of course be granted that under favorable conditions the principle of assigning a distinct target to each section may not be applicable. In other words, the number of target ships may be less than half the number of firing ships, either because the enemy is inferior in strength or placed in a very disadvantageous tactical position. The fire of two sections may then be concentrated on the same target, reducing by half the interval t between the salvos of ships firing successively. A certain amount of confusion will be inevitable; but under such circumstances it would not be advisable to do otherwise, since the maximum offensive power of each ship should be utilized.
THE NUMERICAL STRENGTH OF A DIVISION
With the elemental subdivision thus reduced to a section, the extent of the line occupied by it is reduced to 400 or 500 meters; and consequently the subdivision may be considered well placed for developing the maximum intensity of fire of both ships. This holds even if their column is not quite perpendicular to the line joining their center to that of the enemy. It is true that if the column is not perpendicular to the line joining the two centers (i. e., not in the conventional battle formation), there may be a theoretical disadvantage. In practice, however, this disadvantage is negligible, especially in view of the fact that only a part of the distance between the ships operates to create a difference in the range.
Therefore there is no necessity that the ships of a section should maneuver to maintain the conventional battle formation, that is, to keep in equidistant position.1 It may be established that in general the ships of a section should maneuver in line ahead. The leader should keep the enemy concentration ship on such a bearing as will permit both ships of the section to develop their maximum power of attack. This results in a noteworthy simplification and relief from distractions, and permits the reduction of the distance between the ships of each section to 400 meters.
1Commander Bernotti was a staunch partisan of the formation posizioni equidistant, and was the first in the Italian Navy to discuss it (Rivisti Marittima, March, 1900; March, 1901). The formation grew out of the idea of concentrating the fire of several ships on one of the enemy.
He shows now that in concentrating by sections, the object for which this formation was intended may better be accomplished by line ahead.
We are now able to take a step further in this direction, and show that without serious drawbacks the ships of two sections may be kept in column formation.
Fig. 2 reproduces the situation of two divisions of opposing ships, A and N, each composed of four ships. The ships of N are formed line ahead, and the angle XN1A1is approximately 50°. The ships A are steaming on a line of bearing on a course not indicated in the figure, but such as to keep the line joining the centers of the opposing forces perpendicular to their line. The distance between ships is 400 meters for N and 500 meters for A.
In this situation, the concentration ship for the section A1A2 is N1, while for the section A3A4, the most convenient target is N2; in fact for this latter section there is an advantage in firing on N2 instead of N3, N2, being nearer than N3 (that is, nearer to the middle point of the projection of the line A3A4 on N).
For the sections N1N2, and N3N4, under the conditions of the figure, the target ships are respectively A1and A3.
Now, let us suppose A1N1=8000 meters; then the ranges will be as follows:
Section A1A2 8000 m.
Section N1N2 8000 m. to 8250 m.
Section A3A4 8300 m.
Section N3N4 8500 m. to 8750 m.
If, again, the column A should be in the position A', so that A1N1=4000 meters, we should have the following ranges:
Section A1A2 4000 m.
Section N1N2 4000 m. to 4250 m.
Section A3A4 4300 m.
Section N3N4 4500 m. to 4750 m.
This is enough to show that the theoretical disadvantage for N reduces itself in practice to a comparatively insignificant difference in range.
It follows, therefore, that the line ahead may well be prescribed for the tactical handling of four ships, although it is admitted that for a larger number of ships the difficulties which the line ahead formation involves are no longer negligible.
The force constituted by combining two sections is therefore the greatest that in general may maneuver by the simple method of "follow the leader." Hence it is proper to consider the group of four ships as the tactical unit of a fleet.
The conclusion from what has been said is that the group formed of two sections (four ships) constitutes the proper strength for a division.
What influence will the preceding deduction have on the maneuvering tactics of a fleet?
As has been said, the ships of each division should be in line ahead, and the division leaders should maneuver so as to maintain a favorable bearing both for offence and defence.
The guiding principles for the division leaders to follow, in order to secure unity of control and unity of action, may be defined as follows:
1. The interval between division leaders should be the least that will permit forming the fleet in exact column; if 400 meters is the distance between ships, then the division interval should be 1600 meters.
2. The leaders of adjoining divisions should maneuver so as to keep the division line of bearing approximately perpendicular to the line joining their center to that of the enemy. (For example, in Fig. 3, the division leaders in squadron A will maneuver so as to keep the center-joining line an perpendicular to the line HK.) This is an application of the general principle of the conventional battle formation. In this way, the squadron will attain an advantageous position or one at least equal to that of the enemy, and the ships will not mask each other's fire.
In respect to the leader of the guide division, the leaders of the other divisions should gradually change course and speed so as to keep the angle Hon as nearly 90° as possible.
It would appear easy to do this when there are only two or three divisions. A larger number of divisions might require too great a difference of speed.
A squadron should therefore consist of eight ships or at most of twelve. Beyond that number of ships it would not seem possible to prescribe rules for attaining unity of control and unity of action, at least not without involving the difficulties of a double column. Hence in such cases it would be advisable to form two squadrons which should maneuver separately but coordinately.
TRANSLATORS' NOTE.—In the January Rivista Marittima Lieut. Comdr. De Luigi, of the Italian Navy, defends at length the three-ship division. Commander Bernotti briefly summarizes this defence and answers it. This discussion, though interesting, is chiefly local in its bearing and is therefore not included here.