CHAPTER III. TACTICAL EVOLUTIONS.
48. Tactical Evolutions and Maneuvers.—Let us consider a compact fleet with the units grouped in the manner deemed to be expedient for tactical action, and at the distance from each other which is established as the normal.
In contact out of range the objective of the movements may be that of delaying offensive contact, or of taking a determined position with respect to the enemy, arriving at offensive contact with an advantageous alignment. In general the tracks must be rectilinear. At intervals of time it may be necessary to execute changes of course or of alignment; that is to say, to perform evolutions; the fleet may then be ordered with the maximum exactness, and the control may be completely exercised by means of signals.
In offensive contact we find ourselves under conditions different from those just indicated; we ought to have at every moment an opportune alignment and a suitable inclination of the ships to it; therefore, in general (as has already been pointed out in section 17),an immediate and continuous adaptation of the proper maneuver to that of the enemy is desirable. Limited confidence can be placed in signals, because, aside from other things, they require for their transmission a time that is not inconsiderable, even when use is made of repeating vessels not stationed in the line. In order not to be surprised and disconcerted, it is then necessary to be prepared to maneuver on the basis of simple directives—each division imitating the movements of the one immediately under the orders of the commander-in-chief; and, analogously, the single ships of each division regulating themselves by the one among them that is charged with the conduct of the maneuver.
We must, then, necessarily admit that the evolutions cannot, in general, satisfy the necessities of offensive contact, reflecting (as already results from section 33) that they ordinarily require two changes of course of considerable amplitude, which disturbs the firing; moreover, when an evolution is ordered, it is necessary to foresee what will be the tactical situation at its end, or, after a time that is not ably long, when the naval force is numerous. Such a length requires the prevision alluded to, and, on the other hand, renders it very difficult—the enemy being free to maneuver according to his desire. It is to be observed that, naturally, this prevision is also necessary when an evolution is ordered in contact out of range; however, if in the course of the evolution we do not arrive at offensive contact, we may, at least in part, nullify the effects of an erroneous prevision, by so regulating ourselves as to delay the approach. Finally for the duration of the evolution, the movements of the single units are restricted; and it is clear that this restriction cannot permit the best employment of the weapons and satisfy the variability of the tactical situation. Let us, then, admit the principle that in contact out of range we perform evolutions, and in offensive contact we maneuver; having, in the latter case, as little recourse to evolutions as possible. Definitions.—We shall call tactical evolutions those proper for the government of a fleet in contact out of range, thus distinguishing them from the multiplex evolutions that can be imagined. Under the name of tactical maneuvers we shall include those maneuvers that are required for the control of a fleet in offensive contact.
In this chapter we shall study tactical evolutions, considering successively the hypotheses that the fleet may have a simple alignment and a double alignment. We shall subsequently refer to the case of separated groups in contact out of range.
49. Evolutionary Speed—Reserve of Speed.—As is well known, to the end that a ship may keep in the formation it is necessary for it to have a reserve of speed; or, the normal speed must be somewhat inferior to the maximum speed of the slowest unit. On the other hand, in order to render the evolution as rapid as possible, it seems to us well to establish that, as a general rule, the evolutionary speed shall always be equal to the said maximum speed of the slowest unit. Consequently, when, for instance, we say that the evolution is performed with the speed ratio of 1/2, it is established that the pivot ship reduces its speed, not to one-half of the normal speed, but to one-half of the evolutionary speed.
The minimum reserve of speed that each ship in the formation should have at its disposition must be a fraction determined by the normal speed; or, it must be of greater value the higher is the normal speed; in fact, a ship that is not exactly on the desired line of bearing, in order to get into position, determines by eye the small change of course necessary; but, as equation (3) of Chapter 1 shows, the amplitude of the change of course—and hence the time required to get into the formation—depends upon the ratio between the normal speed and the evolutionary speed, and not upon their difference. Let us admit that the minimum reserve of speed may be defined by the ratio
normal speed/evolutionary speed = 9/10
50. Evolutions to be Considered for a Simple Alignment.—In relation to what we established in section 18, let us consider a naval force composed of two elementary alignments, each of which does not contain more than six ships. Let the naval force be upon a single line of bearing.
As we said in section 12, the formation has of itself no importance. Having admitted this idea to be fundamental for offensive contact, we ought to take it a fortiori as a guide in the study of contact out of range. In the latter, given the objects that we may decide upon, the first element to be determined in relation to them is the course; when the alignment is adjudged to be satisfactory, or when a change of course is urgent, such change is made simultaneously.
This said, let us suppose that the fleet has the proper course, which we will call the advantageous course, and that it is desired to change the alignment. The evolution to be performed consists in a change of polar bearing, which may be executed by one of the following methods:
1st. By changing course in succession (contromarcia).
2d. By oblique courses.
3d. By methods based upon the wheeling of the single column.
51. Change of Course in Succession.—In order to satisfy tactical necessities, from among the ways in which this method may be applied, we should select the one that permits of losing the least distance in the direction of the advantageous course.
The problem being thus set forth, it results there from that the transitory courses during the evolution should not make with the advantageous course an angle greater than 90°.
LetA1….An (Fig. 26) be a line of polar bearing a. A1Z being the initial course—which we will suppose to be the advantageous course—the transitory course must be included in the semicircle X1ZX2, X1X2, being normal to A1Z. Desiring, then, to assume an alignment Y1Y2, it is to be observed: 1st, that it is not well to execute the evolution in inverse order; that is to say, by changing course simultaneously in the direction A1An, which is without the said semicircle; 2d, that, for the same reason, in the evolution in direct order, that is, changing course simultaneously in the direction AnA1, it is not well, after such change, to execute the change in succession in the direction A1Y1, although the angle TA1Y1 is smaller than TA1Y2.
{figure}
FIG. 26
The rules for the evolution are hence the following:
1st. The ships change course simultaneously through the angle toward the ship farthest advanced in the direction of the advantageous course, resulting thus in a column of vessels.
2d. The leading ship,followed in succession by the other ships, changes course in the direction of the new alignment which makes the minimum angle with the advantageous course.
3d. When the last ship has completed the turn in the wake of the leading ship, the ships change simultaneously to the advantageous course.
It is to be noted that the change of course in succession, which constitutes the second part of the evolution just described, can be executed at evolutionary speed rather than at normal speed, because a ship that may have fallen slightly behind may put itself exactly in position by not following exactly in the wake of the one that precedes it, when it makes the turn.
52. Oblique Courses.—With the method by oblique courses, as has already been said in section 33, the extreme ship toward which the alignment inclines, reduces its speed, and the ships change course through an angle given by an appropriate table. If the angle of the change of course were estimated by each ship, that is to say, if it were not sought to determine it with the aid of a table or an instrument, it could only result in the employment of a longer time for the evolution, without any gain in simplicity. The angle of the change of course could be determined as indicated by Admiral Morin in his profound work entitled Degli ordini e delle evoluzioni di' un' armata (Rivista Marittima, 1873-1874); but even in that case the evolution would not be completed in the minimum time.
It might also be prescribed that the intermediate ships of the formation should regulate their speed so as to arrive simultaneously on the new alignment; but the reasons for so doing are insufficient, while, on the contrary, for the case in which it is necessary to confront an unforeseen situation, it is preferable that each ship should arrive on the new alignment as soon as possible, as was proposed by De Gueydon.
The maximum value of the speed ratio that can be adopted in evolutions must be inferior to the value 9/10. established in section 49; that is to say 8/10. On the other hand, as we have already said in Chapter 1, the minimum value that can be adopted for this ratio is ½.
This being the case, it seems logical to perform evolutions with the ratio ½ when the rapidity of the evolution is principally required, and adopt the ratio 8/10 if rapidity must be sacrificed to the condition of losing the least distance possible in the direction of the advantageous course; it is well, however, to make a few reflections in this connection.
Let us indicate by VB the evolutionary speed, and by VB the speed of the pivot ship. Let t' and t" be respectively the times employed in a change of bearing of an amplitude ? with the values ½ and 8/10 for VB/VA. By formula (6) of Chapter I we have:
t”/t’ = Vr’/Vr” (I)
Vr’ and Vr” being the relative speeds corresponding to t' and t" that are deduced by the formula in section 31, which gives Vr; this formula can be written:
Vr=VA 1+(VB/VA)2 -2 VB/VA cos ?
in which ? is the angle of the change of course given by equation (3) of Chapter I as a function of VB/VA and ?1 – w/2; ?1 being the polar bearing on which the ships are found with respect to the pivot ship at the beginning of the evolution.
In the time t" necessary for the evolution with the ratio 8/10 the space passed over by the pivot ship, which we will indicate by p", is given by
P”=0.8VAt”.
Let us bear in mind that 9/10VA is the normal speed; consequently, if the evolution is performed with the ratio ½, the track p' of the pivot ship in the time t" is evidently
p’=0.5VAt’ +0.9VA(t”-t’);
and hence we have
p”-p’ = (0.4-0.1 t”/t’) VAt’ (2)
Let us indicate the ratio p”-p’/ VAt’ by u; which are obtained by means of (2), are assembled in the following table in which ?1 – w/2 is made to vary from 0° to 90°, bearing in mind that with supplementary values of ?1 – w/2, formula (3) of Chapter I gives values of ? that are equal, but with the contrary sign; and hence Vr the corresponds thereto.
?1 – w/2 t”/t’ u
0° 1.4 0.26
30° 2.0 0.20
60° 2.4 0.16
90° 2.5 0.15
These values show that if ?1 – w/2 is included between 30° and 180° -30° = 150°, and if the evolution is such that it is of long duration when executed with the speed ratio 1/2, the advisability of the evolution with the ratio 8/10 is to be excluded, because the greater distance gained in the direction of the course appears to be a negligible advantage when compared with the increase that is realized in the duration of the evolution; in other words, the time necessary for securing the benefit represented by the difference p"—p' is so long that we cannot rely upon the tactical conditions remaining stationary long enough to permit of completing the evolution.
For example, let us suppose the speed V=18 knots an hour, or 558 meters a minute; let ?1 – w/2 = 75° and t’=10 minutes, as is the case with a fleet of ships in line abreast at intervals of 500 meters, that wishes to change the bearing through 30°; we have, then, t”=24 minutes (about), and p’ – p’ = 0.16 x 558 x 10 = 890 meters.
If ?1 – w/2 is less than 30° or greater than 150°, the angle of change ? is greater than that which would be required, for the same value of w, in the case before considered; that is to say, with respect to that case, and with the same method, the evolution is more rapid; and it is to be noted that t" diminishes more rapidly than t' because, as the table shows, the ratio diminishes while u t' increases; and hence the evolution with the ratio A may really be advantageous. For example, for the fleet of 12 ships before supposed, when ?1 = 40° and w=30°, we have t’=7.5 or t”=12 minutes, and p” – p’=0.22x558x7.5=940 meters.
Now let us note that in order to have ?1 – w/2 <30°, it is necessary for ?1 to be between w/2 and 30° + w/2; but since, as a measure of safety, we cannot allow the course of the pivot ship to be crossed during the evolution ?1 must be included between ? and 30° + w/2; or, it must be greater than 150° + w/2.
Moreover, considering that it is necessary to avoid excessively long evolutions, it is well that the evolutions with the speed ratio 8/10 should be restricted to the case in which is not greater than 30°; so that such evolutions, in view of the limits of ?1 just found, may be deemed advantageous for lines of bearing nearer to the column of vessels than to the line abreast.
When ? does not exceed about 10°, t’ is small whatever may be the value of ?1 – w/2, and hence no importance can be attributed to the difference p” – p’; however, as t” is also sufficiently small, the evolution with the ration 8/10 is justified by the possibility, of obtaining the object with the minimum alteration of course and speed. In other words, we may in general affirm the propriety of adopting the ratio 8/10 when the evolution can almost be considered as a rectification of the formation. It is clear that in such case it is not advisable to apply the rule of De Gueydon for the change of course of the pivot ship; the course of the pivot must remain unchanged.
The evolution with the ratio 1/2 is then advisable when ? is of considerable amplitude, and the formation is nearer to line abreast than to column of vessels.
53. Change of Alignment by Wheeling.—I. Admiral Bouet de Willaumez, in his Projet de tactique navale (1855), in which he laid down the basis for the evolutionary systems for steam vessels, in considering the wheeling of a fleet drawn up in line abreast, alluded to the system of pivoting on the center ship, one-half of the vessels going ahead and the other half backing; naturally, he discarded the method, since evolutions cannot be performed by going astern, and he limited the practical methods to those which pivot on one of the extremities of the formation. Nevertheless, the idea of the illustrious admiral can be applied to the wheeling of a column of vessels without need of backing the engines; in such case, as indicated by the anonymous writer in the United Service Magazine already cited (section 33, III), it is possible to change the alignment by pivoting on an intermediate ship of the formation; or, the line may be considered as composed of two parts, one of which has the pivot ship for a leader, and the other has it for the rear ship; and hence the first performs the evolution by executing the wheel on the leading ship, while the other makes the change of course necessary for wheeling on the rear ship.
On the basis of the idea already advanced that, tactically, it is not important to maintain a fixed formation, we may not, in general, assign importance to wheelings; that is to say, it is not necessary at the end of the evolution to re-establish the polar bearing that the formation had initially; however, if the wheeling of a column of vessels can be executed rapidly by pivoting on an intermediate ship, we are induced to, favor this method for changing an alignment, considering the column of vessels as a transitory formation, as is done in evolutions performed in succession. In other words, being upon any line of polar bearing a, in order to change the alignment we can change the course of the ships simultaneously through the angle a, thus bringing them into column of vessels, then execute the wheel on a conveniently selected pivot ship, and afterwards, with another simultaneous change of course, take the direction that is deemed advantageous.
In such an evolution the pivot ship evidently cannot maneuver according to the rule of De Gueydon, because the two parts of the line execute changes of course in contrary directions; hence, the pivot ship must alter the course through the angle w, through which it is desired to change the alignment, and afterwards reduce speed in the desired ratio with the evolutionary speed.
After what has been said in section 33, it is easy to determine the criterion according to which the pivot ship should be selected. Evidently, in order to wheel a column of vessels A1A2 (Fig. 18), the ship B most convenient as a pivot, is the one to which there corresponds an evolution of the same duration for each of the extreme ships, A1 and A2, that are respectively the rear ship and the leading ship. Having demonstrated that A1B/A2B >1, it quickly follows that the point of rotation is ahead of the center of the line. In particular, from the table of section 33, IV, which, for the speed ratio 1/2, gives the values of the ratio t2/t1 between the duration of a wheel on the rear ship, and that of a wheel on the leading ship (or it gives the value of A1B/A2B), we may deduce the ratio A2B/A1A2; that is, the distance of the pivot from the leading ship as a function of the length A1A2 of the line. In fact, we have
A2B/A1A2 = 1/1+ A1B/A2B = 1 + 1/1+t2/t1
Indicating by t3 the duration of the wheel when pivoting on B, it is clear that A2B/A1A2 is equal to the ration t3/t2, the values of which, multiplied by the corresponding values of t2/t0 given by the table of section 33, IV (t0 being the duration of the evolution performed in succession), give us those of the ration t3/t0.
In the following table are set down the values of the two above mentioned ratios.
w t3/t2 t3/t0
15 0.46 0.15
30 0.42 0.29
45 0.39 0.43
60 0.36 0.55
75 0.33 0.65
90 0.31 0.75
These results show: 1st. That with w, greater than 60° the pivot ship may be held to be the one at about one-third the length of the column from the leading ship; while, if ? is less, the pivot ship is the one at about four-tenths of that distance. 2d. That the method of wheeling just cited is advantageous when compared to that performed in succession, especially for values of ? less than 60°.
From what has been said, the ships astern of the pivot ship should change course as in any ordinary wheel on the leading ship; but, for a certain number z of them, the evolution may be simplified by prescribing that they follow the pivot ship in succession on the basis of the following considerations.
As the pivot ship, after having changed course through the angle to, takes up the speed ½VA, a ship that occupies the position z a stern of the pivot, and which follows it in succession, arrives on the new alignment after a time a d/½VA being the distance between two adjacent ships.
To the end that the said time may not exceed that occupied by the last ship of the line in executing the wheel, it is necessary to realize
z d/½VA = t3
Let n be the total number of ships composing the line. The time that would be occupied in following the leading ship in succession at a speed VA is expressed by
t0 = (n-1)d/VA;
and hence we must have
z =< (n-1)/2 t3/t0,
in which the values of t3/t0 that it is necessary to introduce are those to previously obtained. Under the two hypotheses of a line composed of 12 or of 8 units, the number of ships that can maneuver in succession astern of the pivot ship is given by the following table:
w n=12 n=8
15° .. ..
30° 1 1
45° 2 1
60° 3 1
75° 3 2
90° 4 2
So, as an illustration, with a line of 12 ships, wishing to execute a wheel of about 90°, the first four ships and the last three must perform the evolution at a speed VA, while the five center ships must keep the speed VA.
In general, the difference of speed required for the center ship and for those at the extremities shows, as is noted by the English writer already mentioned, that this method of changing the alignment is particularly advisable when the limited speed of the fleet is due to considerable differences in the maximum speeds of the various ships. In fact, it has already been established that the normal speed must be of the maximum speed of the slowest unit; it has, furthermore, been affirmed that the evolutionary speed may be equal to the said maximum speed. This limit cannot be exceeded in evolutions performed in succession, and in those with oblique courses wherein one of the extremities of the formation is made the pivot, it being necessary that the angle of change of course be the same for all the ships. It is clear, however, that in order to obtain the maximum rapidity in wheeling the column of vessels by the method described, if the divisions composed of the fastest ships are placed at the extremities, such ships can avail themselves, not only of the reserve of speed defined in section 49, but also that which results from the difference between the normal speed of the fleet and the maximum speed of the said divisions.
If the ratio between the maximum speed of the central division and the maximum speed of the extreme divisions does not exceed 8/10 from what proceeds there results, within certain limits, the possibility of wheeling the line without loss of speed to the fleet as a whole, by executing the change of course ? in succession with the central division, and by the ships of the extreme divisions going to their positions with the reserve of speed. With the speed ratio 8/10, this method may be held to be advisable when ? does not exceed 30°.
II. Let us suppose our fleet to be on any line of polar bearing a; let OS (Fig.27) be the alignment, OR the course steered; and it
{figure}
FIG. 27
is desired to pass to the alignment OS', inclined to the present alignment at the angle w, pivoting on one of the extreme ships. Analogously to what has previously been said, we can have recourse to the column of vessels as a transitory formation, by changing course together on the initial alignment, and then wheeling the column on the rear ship or on the leading ship, changing course in the first case through the angle ?c in the direction of the new alignment, and in the second case through the angle (At in the contrary direction; ?c and ?t being the angles given by formula (4) and (5) of Chapter 1. Let us observe, however, that the ships being, by hypothesis, already inclined by the angle a in the direction of the new alignment, the angle of change, instead of ?c, is ?c – a the case of pivoting on the rear, and a+ ?t when pivoting on the head. Taking this into consideration, the evolution may then be executed in the same manner indicated in Chapter 1, for wheeling a column, without any complication whatever; because, according to the case, it suffices to subtract from, or add to, the angle of the change of course taken from the table for wheeling the column, the polar bearing of the formation.
It is obvious that the evolution is executed analogously if the new alignment is inclined the opposite way; thus, in Fig. 27, if the new alignment is OS", the angle of change for wheeling on the rear ship is a- ?c, and for wheeling on the leading ship it is a— ?t.
Having thus generalized on the wheeling of the line, let us look into the importance to be attributed to such an evolution.
The party A (Fig. 28) has an alignment A1A2 in the direction of the course CNCN' of the enemy's center; it makes its alignment rotate through an angle w, pivoting on the extremity A1 farthest from the adversary. Since we leave it undetermined whether, with respect to the course of the fleet, the said extremity is farthest ahead or farthest astern, our reasoning is general and tends to establish the advisability of wheeling either on the head or on the rear.
{figure}
FIG. 28
For simplicity's sake, let us suppose that A1 remains stationary during the wheel; the center CA of A takes the position CA', and the new inclination of the alignment, counting from the line joining the centers, A2’CA'CN', which we will indicate by ?. As is an exterior angle of the triangle CA/CN'A1, we have
?=w+CA’CN'A1; and hence ? > ?.
The advisability of wheeling upon A, would hence seem to result from the fact that, while the alignment rotates through w, it really approaches the fundamental position through an angle greater than w; while if the wheel were made about the extremity A2, the contrary would happen; and, finally, if the rotation were made about CA, a would be equal to w.
In practice, in wheeling the alignment the pivot A1 would not remain stationary, and, by reason of its movement, the angle ? might be increased or diminished according to the circumstances of the case.* So, also, the wheel on the intermediate ship, as has been said in Part I of this section, would not be made exactly about CA; but all this does not weaken the general reasoning which would lead us to believe it advantageous to take as a pivot the extremity of the formation farthest from the enemy.
It is now necessary to determine the value of the difference ?-?; this is clearly at the maximum when ?=90°; and, A1A2” being the position of the alignment of the party A corresponding to such an hypothesis, from the triangle CA"CN'A1 we get
tan ? = t/½S,
S being the length of A's alignment, and r the distance CA" CN', or the distance between the centers after the wheel. Supposing r= 15,000 meters, and S=5000 meters, we have ?=80° (about). Since the maximum value oft he difference ?-? is thus 10°, it appears to be negligible, considering the rapidity with which the alignment may be rotated by pivoting about one-third of the length of the line from its head. Also, under the hypothesis r=10,000 meters, we have ? =75° (about), or ?-?=15°. The importance to be attributed to the wheel when pivoting on one of the extremities is hence restricted to that which results from the study made in Chapter 1, in which it was established that, within certain limits, it may be preferred to the evolution in succession when the line is very long.
As has been said, on account of the rapidity, pivoting on the ship about one-third from the head of the line is preferable to pivoting on one of the extremities. Nevertheless, being on a line of polar bearing, the evolution just mentioned may be advisable, as it avoids the initial passage to the column of vessels. Having regard to the amplitudes of the changes of course that the method requires it is seen that it is best to pivot on the rear ship if the course is inclined in the direction of the new alignment, and on the leading ship if the course is inclined in the opposite direction.
54. Angular Alignments.—The angular orders, so much esteemed when the ram was considered the principal weapon, seem
* If A1 were the rear ship, the angle ? would also be increased, because the displacement of the pivot would be in the direction A1 A2'; while, if A1 were the leading ship, the displacement of the pivot would be in the direction A2' A1; on the other hand, since we know that the evolution on the leader is more rapid than in the other case, we must conclude that we are confronted with contradictory elements. (Author's note.)
today to acquire new importance, but on a different basis, for the reasons adduced in Chapter III of Part I (sections 18 and 20). As we there pointed out, the angular alignments are advisable in offensive contact for the purpose of having each of the elementary portions of a composite alignment in fundamental tactical position.
This advisability commences in contact out of range at the moment when the limit of offensive contact is about to be crossed, with the application of the following rule, the necessity for which seems obvious.
In contact out of range the fleet must be on a single line of polar bearing; if this is such that, when it is about to arrive at firing distance, one of the elementary alignments is in fundamental position, then, with such division taken as a pivot, the other elementary alignment may be changed so as to establish offensive contact in the most advantageous manner.
{figure}
FIG. 29
On the basis of this rule, under the hypothesis that the enemy has his forces compact, the limits within which the inclination i (Fig. 29) of the elementary alignment may vary, can be deter- mined. Let CA be the center of the alignment of the party A, and let CA' and CA" be the centers of the elementary alignments.
Evidently the maximum value of i results under the hypothesis that the alignments must be in fundamental position with respect to one and the same elementary alignment of the enemy's formation which has its center at CN. In such case we have
CA‘CNCA”= i
and hence CA’CNCA”= CACN sin i/2
Indicating by n the number of ships in the A party, by d the distance between adjacent ships, and by r the distance CA CN, we obtain
CA’CA= CACA = (n-1)/4 d;
therefore we have
sin i/2 = n-1/4 d/r.
Making n= 12, d=500 meters, r=10,000 meters, we get i=16° (about). We may then hold i=20° as the maximum value of i; hence the evolution may generally be executed by oblique courses with the speed ratio 8/10. Evidently the pivot, instead of being a single ship, is composed of all the ships of the elementary alignment that it is desired to leave unchanged. The fact that the pivot is an assemblage of ships, renders inadvisable the application of the rule of De Gueydon for the double change of course.
It is easy to understand that, in order to obtain the object of the evolution, it is desirable that the ships forming part of the pivot should keep a course parallel to, and in the same direction with that of the enemy. If he makes a wide change of course, it is best to interrupt the evolution, assume the course that is deemed best, and then make another attempt.
When the angular) alignment is brought about by the necessity of confronting an enemy broken up into independent groups that are not echeloned in distance—as represented in Fig. 11—the angle between the elementary alignments may be greater than that just found; in such case it is generally best to assume the angular alignment by interrupting an evolution in succession.
55. Evolutions with a Double Alignment.—One may be induced to perform evolutions with a double alignment (section 19), in contact out of range, by one of the following considerations:
1st. In contact out of range, as well as in offensive contact, it may be desired to keep the forces massed in that way.
2d. It is evident that one can perform evolutions more easily with a simple than with a double alignment of the same length; but it might be held that, given a certain number of ships, by placing them in double rather than in simple alignment, greater evolutionary facility might be acquired by virtue of the shortening of the line. Whenever evolutionary advantages with the double alignment present themselves, it might be employed in contact out of range, passing at the proper moment to the simple alignment in order to come into offensive contact.
A fleet in double alignment may be considered as formed by groups of four ships each in parallelogram (system of Labres *),
* See the resume of Commandante Bonamico in Rivista Marittima, August-September, 1902.
or of three ships in a triangle (system of Fournier *); finally by groups of two ships, one in each line (twin system).
Let us consider evolutions performed by the ships in succession. The maximum simplicity and evolutionary rapidity would seem to be obtainable by causing each group of four ships to maneuver by simultaneous changes of course; in fact, small changes of the course of the naval force may be obtained by having each group make the change of course when it arrives in the wake of the preceding group. However, it is easy to see what inconveniences are encountered in so doing. Let us suppose a desire to change the alignment when the ships are on two lines of polar bearing and the lines joining the corresponding ships are normal to these lines of bearing, the distance between the lines being equal to the distances between ships, so that each group of four ships forms a square. By making all the ships of the fleet on the actual alignment change course simultaneously, we have the double column. In Fig. 30 there is represented a fleet composed of two groups that are already in that formation, and there is also shown the formation that results from a change of course in succession, following the rule above indicated. As is seen in the figure, the result is that the ships are no longer in two lines, but in four; and it is clear that they still remain in four lines when all the fleet executes the simultaneous change of course in order to return to the original course, or to take up a new course that is deemed advantageous.
{figure}
FIG. 30
This sufficiently indicates that the method is not advisable, for the following reason:
* See Rivista Marittima, Vol. IV of 1907. In Fournier's system, the number of ships in one line of the alignment is half of that in the other line. With this system simultaneous changes of course are abandoned. (Author's note.)
In offensive contact, to the end that all the ships may fire, it is a necessary condition that they be not upon more than two lines. When the fleet is in two lines in contact out of range, on opening fire, it may be easy for the ships in the outer line with respect to the enemy, appropriately to modify their positions with respect to the ships in the inner line, so as to be able to fire through their intervals. This already constitutes a difficulty that, in practice, is not inconsiderable; but plainly we shall expose ourselves to the gravest risks if the matter is still further complicated by the fact that the ships are in more than two lines at such a critical moment.
Analogously, if the groups of three ships each were maneuvered by simultaneous change of course, we should find ourselves forming three lines; which, for the same reasons, we believe are to be avoided. In evolutions performed in succession, the method of simultaneous changes of course may be adopted with the twin system only, for small changes of alignment. Indeed, let a, b, a1, b1, (Fig. 31), be four ships of the double column; when the ship b arrives in the water in which a has executed the change of course, the ship a, is in the position a1’ such that a1a1’=a1a=d. To the end that, in the new alignment, the distance between the ships of the two lines may not fall below d, it is necessary to have aa1’=>d, or w=<30°.
This being said, we deem it indispensable that the evolutions of a double alignment should be executed on the basis of the following fundamental conditions:
1st, that the fleet be always in two lines. 2d, that, in general, the corresponding ships of the two lines should have each other bearing normally to the alignment; in fact, from this position the ships of the outer line with respect to the enemy, can, at the opportune moment and with the least possible difficulty, take the necessary positions for firing; and in this way we shall avoid a long alignment.
Furthermore, we shall hold that, generally, the number of ships composing the two lines should be equal, given the essential object which we have in view which is that of shortening the line.
The fleet may be drawn upon two lines of polar bearing a; a being any angle whatever, but the same for both lines. Let us suppose the simultaneous change of course for passing to the double column to be already executed, as in the first position of Fig. 30, and let us see how, and in what time, the change of direction of the said column can be completed, in order afterwards to take up the advantageous course by a simultaneous change of direction.
From what has been demonstrated in section 41, it results that if two ships A and B, that have respectively the speed VA and VB keep each other constantly bearing abeam, the tracks described by the mare concentric circumferences. Letting ?A and ?B represent the radii of the circumferences AA' and BB' (Fig. 32), described respectively by A and B when VA>VB, and indicating by d the distance between the two ships (which remains constant dur-
{figure}
FIG. 32.
ing the movement), from formula (II) of Chapter I, substituting d for r there in, and making a=?=93°, we have
?B=d/ VA/VB - I
while
?A= ?B +d =VA/VB ?B.
To the end that the condition ?B=d may be realized, it is necessary to have VA=2VB.
Now let it be noted that, between ships in formation, the tactical radius about equal to the distance d is that which is ordinarily employed when d is between 400 and 900 meters. It results, then, that, when in double column, the leading ship B of the inner line, with respect to the change of direction, puts his helm over, he must reduce his speed to one-half that of the outer line, of which the leading ship A, at evolutionary speed, must steer, keeping B, by sight vane, constantly abeam. The ships of the outer line must keep up the speed in order to keep themselves abeam of their corresponding ships.
If n is the total number of ships in the fleet, each line is then composed of n/2 ships; and hence the time t occupied by the evolution is expressed by
t= (n/2 - 1)d/VB = (n-2)d/VA.
If, instead, the fleet were in single line, the time occupied would be (n-1)d/VA; which shows that the above mentioned method requires a time only slightly different from that which would be occupied if all the ships were in a single line, and exactly corresponds to the time occupied by a single line having one ship less.
The method just indicated is general, and it is necessary to have recourse to it when the angle w, through which it is desired to change the alignment, is of considerable amplitude; but, when ? is within certain limits, one can maneuver with greater quickness with the ratio 8/10 between the speeds of the two lines, in the following manner:
{figure}
FIG. 33.
The ship B, leading the inner line (Fig. 33), changes course through the angle ? in the desired direction, and assumes the proper speed for the above-mentioned ratio; the leading ship A of the other line executes, with respect to B taken as a pivot, an evolution by oblique course, in order to bring itself again on the polar bearing 90°; that is to say, it completes—as is said in section 33, III—a wheel in line abreast; when A has made the wheel, that is, when it has arrived at the position A', it steers a course parallel to that of B and assumes the speed of B. The ships of each line follow their respective leaders in succession, and those of the outer line opportunely regulate their speed in order to keep themselves abeam of their corresponding ships. It is clear, as Fig. 33 shows, that the change of direction to the new alignment will be completed when the last ship of the outer line arrives at A'; and, at the same time, the last ship of the inner line will beat B.
The duration of the evolution is hence
t=(n/2 – I)0.8VA + tc =(n-2)d/1.6VA+tc
tc being the time necessary for the wheel of AB.
To the end that the duration of the evolution with the method may be less than that corresponding to the method by concentric circumferences before alluded to, we must have
(n-2)/1.6 d/VA + tc < (n-2)d/VA
Making d/VA = t0, this inequality is transformed into another:
tc/t0 <0.38(n-2).
The formula that gives the duration of the wheel of two ships in line abreast at the distance d, by virtue of what has been demonstrated in Chapter 1, is
tc= 2d sin w/2 / VA 1+(VB/VA)2 VB/VA cos (?-?)
in which ? is the angle of change of direction for said wheel, which angle is equal to ?+?; ? being the angle obtained from formula (3) of Chapter 1, by placing in it ?1=90° + ?; in this way we get
? = /2 + arc sin (VB/VA sin ?/2),
wherein, in the case we are discussing, we must put VB/VA=0.8.
There is thus obtained the values of tc/to which are set down in the following table:
? tc/to n
15° 1.31 6
30° 2.59 10
45° 3.48 12
60° 4.54 14
75° 5.08 16
90° 5.87 18
With the values of tc/to, taking into account the inequality above to deduced, the values of n in the third column are calculated; which values indicate, for each value of w, the minimum number of ships of which the fleet must be composed in order that the evolution performed in succession, following the wheel of the leading ships, may be advantageous with respect to the evolution by concentric circumferences.
It results from the preceding that, in evolutions performed in succession, a fleet must be very numerous in order that it may be maneuvered on a double alignment with greater rapidity than on a single alignment. Indeed, if the number of units is not very considerable, the angle w must likewise be limited in order that the method by wheeling the leaders may be sensibly advantageous over that by concentric circumferences; which, in its turn, occupies a length of time not sensibly different from that required by a simple alignment. So, in order to fix the ideas, let us note that with twelve ships on a simple alignment, the evolution would require a time II d/VA; while with the method of concentric circumferences the time would be 10 d/VA, and, with the wheel, for ? = 45°, there would be a duration of 9.7 d/VA. However, the advantage of this last method is rendered sensible with smaller values of ?. The evolution by oblique courses, in order to satisfy exactly the two conditions established as fundamental, must evidently be executed according to the following rules:
1st. Simultaneous change of course in the direction perpendicular to the alignment. The fleet is thus arranged in two lines abreast, and the corresponding ships of the two lines are in column of vessels.
2d. The ships of the first line make a wheel in line abreast of the amplitude through which it is desired to change the alignment; the ships of the second line follow in succession, opportunely regulating the speed in order to maintain the distance from the corresponding ships of the first line.
3d. The advantageous change of course is assumed with a simultaneous change of direction.
It is needless to demonstrate that this evolution is little adapted to tactical necessities.
In double column the alignment might also be changed by wheeling each of the two columns so formed; but it is to be noted that there is applicable to such a case the observation already made in this section in connection with evolutions performed in succession by means of simultaneous changes of course of the successive couples of ships; that is to say, the said wheel must be less than 300 in order that the distance between the ships of the two lines at the end of the evolution may not fall below the normal distance.
We are now able to formulate the following conclusions concerning the tactical management of a double alignment.
Having a number of ships greater than twelve, the double alignment is convenient; evolutions with it must generally be performed in succession. Evolutions by oblique courses are long and complicated; hence it is difficult to take up in that way an angular alignment, and when the latter is deemed necessary, it must be assumed by interrupting an evolution performed in succession.
With about twelve ships or less, the double alignment would allow some advantage over the simple alignment in the case of evolutions performed in succession; but it must be borne in mind: 1st,that this advantage is sensible only within very narrow limits; 2d, that with the fleet on a double alignment, evolutions by oblique courses are performed with great difficulty; 3d, that, desiring to pass to a simple alignment at the moment of coming into offensive contact, an evolution would be necessary, which, on the other hand, would not be necessary if the forces were kept on the simple alignment from the start. In short, with a not very numerous force, keeping it, in contact out of range, on a double, instead of on a simple alignment, there would be a diminution rather than an increase of the maneuvering qualities of the fleet.
Finally, as pointed out in section 19, the double alignment may be advisable for the purpose of using antiquated ships in the second line; it is clear, however, that the number of such ships must be limited, so as not in the least to encumber the maneuvering of the line composed of modern ships. The double alignment formed in this way, can be maneuvered-as a simple alignment when the antiquated ships are not deficient in speed, and when there is only one of them for every three or four ships of the real line of battle. The said ships of the second line, without any suggestion of exactly determined positions, will regulate themselves in the most opportune manner in order not to embarrass the maneuvering of the principal line.
56. General Considerations Concerning the Evolutions of Compact Forces.—Admiral Makaroff notes how it may be well to interrupt an evolution that is in progress. "While the fleet is changing its formation," he writes, "it remains in a transitory state of maneuvering, and the admiral can undertake nothing during that time without risk of causing confusion. A case, however, may arise wherein a change of formation ought to be arrested in order that all the ships may execute a simultaneous change of course. Short signals should be employed, and we proposed that the signal 'Come along!' (Via!) be hoisted. All the ships must then, as quickly as possible, assume a course parallel to that of the admiral and thus afford him the possibility of maneuvering."
These considerations are to be borne in mind. It may be important to interrupt an evolution when a change of course is urgent, or because the new alignment signalled is no longer deemed opportune. As the ship of the commander-in-chief may not be at an extremity of the line, let us establish that, in interrupting an evolution, the ships must assume a course parallel to that of the guide ship (regolatrice).
The possibility that an evolution by oblique courses may have to be interrupted, and that for this reason a disorderly formation may result, shows us the special importance that must be attached to evolutions performed in succession; indeed, with this method, after having changed course on the initial alignment and while the ships are changing direction successively in order to arrange themselves on the new alignment, if it is discovered that the said new alignment is not satisfactory, the leading ship can change course, causing itself to be followed in succession in order to form another alignment. Hence, evolutions performed in succession do not require prevision of the tactical situation at the end of the evolution in the same degree in which such prevision is required by the method of oblique courses.
Between two fleets opposing each other which at any given instant may have alignments equally inclined to the line joining their centers, differences may be created by the following causes:
1st. Difference of speed; in fact, with equality and simultaneity of maneuvering, the swifter party can deploy a greater number of ships.
2d. Difference in the length of the alignments; when they are of the same kind (simple or double).
3d. Delay in the execution of the counter movement.
This being the case, of the two adversaries, we will say that the better maneuverer is the one that has the greater speed when the two alignments have equal lengths, or that has the shorter alignment when the speeds are equal.
It is easy to admit that, for the party that is the worse maneuverer—which we will indicate by N—it is well, on sighting the enemy, to assume an alignment normal to the line joining the centers (the fundamental position), while for the party A, the better maneuverer, it may be well to assume a different alignment.
In short, let us suppose that, in this last case, the worse maneuverer does not assume an alignment in the fundamental position, but contents himself with keeping an alignment equivalent, to that of the enemy. By virtue of his better maneuvering qualities, the party A, on coming into offensive contact, can assume an alignment in the fundamental position with greater celerity than the enemy, or can acquire an advantageous initial position.
The interest that the better maneuvering party may have in assuming an alignment different from the normal to the line joining the centers, lies in the probability of leading the enemy into error.
Two cases, then, may present themselves to the better maneuvering party A: 1st, the enemy's alignment is not in the fundamental position; 2d, the enemy's alignment is in said position.
In the first case, it is well for the party A to assume, on sighting, an alignment equivalent to that of the enemy, changing it at an opportune moment in order to be in an advantageous position on coming into offensive contact.
In the second case, it is clear that the greater the amount of maneuvering, the more A can draw advantage therefrom. In other words, it is well for A to move toward one of the extremities of the enemy's line, obliging him to maneuver in his turn in order to keep himself in the fundamental position; in this way A can make an advantageous entry into the zone of fire. The counter movements of N will naturally be inspired by the idea of not allowing the enemy to arrive at firing distance in a superior position; and for this purpose he must have recourse to changes of bearing, keeping the enemy abaft the beam. Under such conditions each of the adversaries will seek, in maneuvering, to lose the least ground possible in the direction of the advantageous course, unless they are so near to the distance for opening fire that they must seek rapidity of evolution above everything else.
On the basis of what has been said, we must hold that unless one of the parties is, to a certain extent, passive, the phase of contact out of range will be a phase of active maneuvering, and will produce differences in the initial conditions of position on the establishment of offensive contact. In the following chapter we shall see how this initial situation may affect the tactical maneuvering.
{figure}
FIG. 34
57. Independent Groups in Contact out of Range.—The breaking up into groups, already alluded to in section 20, appears to be opportune as regards maneuvering, for the following reasons:
1st. The duration of an evolution of a compact fleet is proportional to the length of the alignment, with equality of form of the latter.
2d. By placing the swiftest divisions at the extremities of a line, as has been said in this chapter, the utilization of their speed may be obtained, but only in some special case. In maneuvering by independent groups we may, on the other hand, tend to draw the maximum return from the maneuvering qualities of each group, in a continuous manner, when each of them is sufficiently homogeneous as regards speed.
Let us now consider the maneuvering of a fleet formed by two independent groups, opposed to a compact fleet, in contact out of range; bearing in mind that we have already recognized the necessity, in offensive contact, of avoiding the echeloning of groups in distance.
The speed of a fleet being determined by that of its slowest unit, it is necessary to distinguish two cases:
I. Each of the independent groups has a speed superior, or at least equal, to that of the party that remains compact.
II. One of the independent groups has a speed inferior to that of the enemy's fleet.
Under the first hypothesis, if the forces that maneuver by groups sufficiently understand each other, so that, although independent, they may rely upon maneuvering in a co-ordinate way, from the maneuvering by groups the above mentioned advantages may really be hoped for, although the enemy maneuvers well. A group will maneuver so as to be at the same distance from the enemy's center as the regulating group, keeping the most opportune alignment according to the rules already established. Although, with regard to the momentary positions, an inferiority of conditions for the compact fleet does not exist—as we have pointed out already— still we must hold that it may result in practice, because the compact fleet is the poorer maneuverer.
In the second case, in order to discover the dangers of breaking up into groups, it is necessary to suppose that the enemy maneuvers in the way that is best for him. Let CN, CA’ and CA" be respectively the positions of the centers of the party N that remains compact, and of the groups A' and A" in to which the party A is divided: The speed VN of the party N is greater than the speed VA' of the group A'. From what was demonstrated in Chapter I, it readily results that if N follows a course CNX, such that the polar bearing XCNCA' is equal to or greater than 90°+ arc sin VA’/VA the distance CNCA' continually increases, what ever may be the course of A', because this is the case in which for the slower party, the problem of approach admits of no solution.
This said, it is clear that the course of N may be such as to avoid the approach of A',* producing at the same time the removal of N toward A".
Under such conditions, if offensive contact is brought about, it will be between the compact party and one of the groups of the other combatant; and in order properly to understand why, in such case, A has not the advantage in maneuvering power alluded to in the hypothesis previously discussed, it is well to reflect that, if the course of A" is favorable to the approach, the party N, given its presumable superiority with respect to such group, has to trouble itself about the alignment in a much smaller degree than would be required against an adversary of superior or equal strength.
These considerations suffice for concluding:
1st. The necessary condition for breaking into independent groups is that each group shall have a speed not inferior to that of the enemy's fleet.
2d. When the enemy is broken up into independent groups, and one of his groups has a speed inferior to that of our total force, the conduct of our force must be conformed to the rule of moving in the direction of the swifter group, thus avoiding the nearer approach of the slower group.
* The course of N must naturally be established, taking in to account the length of the formation; that is to say, it must be the most opportune for the ship that could most easily be approached by A'. (Author's note.)
CHAPTER IV.
TACTICAL MANEUVERS.
58. Maneuvers in Column of Vessels.—As has been pointed out in section 48, the fundamental conditions which the tactical maneuver sought to satisfy are the following: 1st, not to disturb the firing; 2d, allow the immediate and continuous adaptation of the proper maneuver to that of the enemy, each ship imitating the movements of the guide ship as a directive.
It is clear that the simplest tactical maneuver that has the requisites enumerated, and which permits of keeping the fleet perfectly ordered, is the one performed in succession in column of vessels.
For these reasons the importance that is generally attributed to the column of vessels is justified. It is well to note, however, that, conformably to the idea several times repeated, a line of conduct contrary to the spirit of modern tactics and binding one to a fixed formation could be followed; and so, when there is a question of the column of vessels, it is generally to be understood that we do not refer to the ships in that formation keeping the course constant for long intervals, but it is implicitly the idea that the course of the leading ship is generally changeable in a slow but continuous manner, conformably to the standards established for an isolated ship; hence we refer to maneuvering in column of vessels rather than to the formation of that name.
Such maneuvering appears the more worthy of consideration inasmuch as the adversaries in the recent Russo-Japanese War confined themselves to it; its importance is incontrovertible, owing to the fact that it requires the minimum amount of preparation on the part of the commander; so that it is indispensable to adopt it when one has at his disposal forces that have had but little drill; but outside of this case, it is well to put the prejudicial question, asking ourselves if the said form of maneuvering is always advisable, so that, admitting its simplicity, we may excuse ourselves from studying other forms.
Against an enemy in column of vessels, the criteria established in section 15 for the selection of ships upon which to concentrate the fire, must be supplemented by taking also into account, besides the firing distance, the disorder that is produced in the enemy's formation by obliging one ship to fall out of the line rather than another. The advisability of each elementary alignment concentrating its offense on the leading ship of the corresponding division of the enemy rather than on the rear ship is evident, unless, in firing on the rear ship, it is possible to carry on the firing at shorter distances. It is apparent, then, that, as between two adversaries in column of vessels with courses parallel and in the same direction, the advantageous position must be held to be the one farther advanced in the direction of the course.
{figure}
FIG. 35
Let us consider the hypothesis that the fleets opposing each other, both in column of vessels, have, in offensive contact, alignments in the fundamental tactical position. From what has just been said in regard to concentration, if neither of the adversaries desires to change the distance, they will maneuver in such fashion that their respective center ships may have courses perpendicular to the line joining the centers, and that each may steer in the direction toward which the enemy is moving. Having alignments of the same length, in order to apply this criterion the two adversaries move initially with courses parallel and in the same direction, and the corresponding ships of the two lines will have each other mutually bearing abeam.
If a difference of speed exists between the two adversaries, the swifter party will gain in the direction of the course, thus tending to acquire an advantageous position.
It is evident that each of the two adversaries will seek to maneuver in order to keep itself in the fundamental position. Fig. 35 shows such an object attained; the centers of the alignments have each other constantly bearing abeam. The alignments are, as we already know, concentric circumferences; the ratio of their radii is equal to the ratio of their speed, and the radius of the inner circumference is expressed by r/VA/VB-1, r being the distance between the centers, VA and VB the respective speeds (VA > VB).
{figure}
FIG. 36
The figure corresponds to the hypothesis r=6000 meters, VA/VB=1.5 for the usual interval of 500 meters between ships. As shown by this, the situations of the two adversaries may be considered as equivalent; so much the more so if the speed ratio is inferior to the one supposed.
A situation nearly like the one indicated, and which is often discussed by the students of tactics, is realized when the two leading vessels, steering by sight vane, mutually keep each other bearing abeam; the radii of the circumferences are still those above mentioned, with the difference, however, that in this case r is the distance between the leading ships.
There is thus produced the tactical situation of Fig. 36, which must be held to be advantageous for the swifter fleet for the following reasons: 1st, the center of such fleet is removed forward of the beam of the enemy's center; 2d, the alignment of the said fleet is concave, while that of the other is convex, which causes it to be fall that some ship does not present a sector of maximum offense. Such advantages increase with the diminution of the distance and with the increase of the ratio VA/VB.
With the supposed data, as the firing distances marked in the figure show, the swifter fleet has a sensible advantage; but the value VA/VB=1.5 is certainly greater than those that are realized in practice; we may, therefore, affirm that, in general, by making the above mentioned maneuver, the two adversaries are in equivalent tactical situations which will remain stationary. Since the situation of the fleets is comparable to that of two single ships opposing each other and which constantly present the beam to each other, by analogy with what we said in Chapter II, we cannot hold it to be rational.
We are thus in condition to affirm that, against an enemy maneuvering in column of vessels, we may not presume, by imitating him, to acquire an advantageous tactical position, even if we possess a notable advantage in speed, unless we have also a notably shorter line. Indeed, Figs. 35 and 36 show how two adversaries that present to fire sides of opposite names may be in equivalent positions; it happens analogously between two adversaries who are in fundamental position in column of vessels, with courses parallel but in opposite directions, each of whom changes direction in succession with intent to assume an advantageous position. In this case the alignment of the slower party also turns its concave side to the enemy.
It is readily seen that, for changing the distance, maneuvering in column of vessels is hardly advisable. For such purpose, let us consider the ships of an elementary alignment that concentrate their fire on one of the enemy's ships. In order that the concentration may be possible, it is necessary for the ship nearest the said enemy's ship to have it bearing in a direction near the beam; sufficiently near, at least, to allow the most distant ship to fire in a limit direction of a sector of maximum offense.
Let us refer to what we noted in section 37 concerning the radii of curvature.
If the two adversaries expose to fire sides of opposite names, the radius of curvature of the track described by the party that maneuvers in column of vessels is necessarily very great, and hence the track may practically be considered rectilinear for a segment of a length equal to that of an elementary alignment.
This being the case, solving the triangle formed by the alignment and the two lines joining its extremities with the said enemy's ship, it is perceived that if, for example, the sectors of maximum offense extend to 45° from the beam, the nearest ship must hold the said enemy's ship by sight vane in a direction at least 60° from the longitudinal axis. In such case, the ships maneuvering in succession in column of vessels are in the condition of a single ship whose sectors of maximum offense do not extend farther than 30° from the beam; or, maneuvering in succession, one may not generally rely upon controlling the development of the action.
When the two adversaries present to fire sides of the same name, the radii of curvature are greatly reduced; but, even if the concavity of the alignment toward the enemy is sufficient to annul the above mentioned inconvenience, it does not do away with the fact that the alignment of the party that maneuvers in succession is inclined to the line joining the centers; while, if the enemy's alignment is in fundamental position, it is obvious that he can oppose changing the distance by opportunely inclining his ships on the alignment.*
* Whoever wishes to study the question in a theoretically more exact way may profit by the knowledge of the following theorem: If two ships steer keeping themselves on constant polar bearings, not only is the indicator of relative movement an equiangular spiral, as we have already had occasion to mention (see note to section 36), but the tracks actually followed by the two ships are also equiangular spirals which are inclined at the same angle with the radius vectors leading from the pole which is common to both. The Angle of inclination of the spirals, adopting the usual symbols, is given by the formula
tan i = VB sin ? – VA sin a / VB cos ? – VA cos a
It results from this that, if one of the two ships is followed by others in succession, the alignment is on art arc of an equiangular spiral.
Lieutenant L. Tonta has occupied himself with this theorem in a valuable article in the Rivista Marittima of March, 1901. The question has been discussed in France in divers articles published in the years 1875, 1876 and 188o in the Revue Maritime; the results of these studies are set forth in Chapter II of Manuel pratique de Cinematique navale by Comdr. L. Vidal (19o5). In practice, however, for the length of the alignment, the equiangular spiral may be considered as an arc of a circle the radius of which is given by formula (ix) of Chapter I. (Author's note.)
Hence, maneuvering in succession may lead to a disadvantageous situation; it lessens the capacity for tactical initiative, because in adopting it we are obliged to change the alignment, when all that is necessary is a change of course.
Evidently, the inconveniences of the column of vessels are increased with a composite alignment; that is to say, the greater the number of ships that follow the leading ship.
The advisability of having the ships inclined to the alignment has been alluded to. In general, the idea of keeping the alignment constant for considerably long intervals of time, changing the inclination of the ships to it according to need by means of simultaneous changes of course, does not seem acceptable, because this may permit an adversary who maneuvers in column of vessels to take advantageous positions; this means, opposing a rigid alignment to another eminently flexible; and, for simultaneous changes of course, signals are rendered necessary.
It would, therefore, seem advisable to establish maneuvering in column of vessels as normal, yet not excluding fighting on lines of bearing because of the simultaneous changes of course that may eventually be required; but the defects which we have recognized as attributable to maneuvering in column of vessels lead us to seek a better system.
Maneuvering by simultaneous changes of course presents the aforesaid inconveniences when the changes are intermittent; but we have already alluded (section 17) to a form of alignment (at equidistant positions) which appears susceptible of being maintained in fundamental position; let us seek to develop this idea by procuring the elimination of the inconveniences of maneuvering in column of vessels without falling into that of rigidity of alignment.
We propose to see whether it is allowable to hold as normal the maneuver known as keeping the alignment at equidistant positions, having recourse to the column of vessels as a transitory formation for the evolutions.
Such importance as a transitory formation may be admitted without further argument, observing that, if it is necessary notably to change the alignment, the evolution must be such as not to render perilous the effects of an erroneous prevision of the tactical situation at its end; or, at such a moment, it is best to be in column of vessels. The evolutions that we must examine for the change of alignment in offensive contact are thus reduced to that performed in succession and those based upon wheeling the column of vessels (section 53).
59. Maneuvering at Equidistant Position.—By virtue of what we said in section 17, an elementary alignment opposed to another may practically be considered an arc of a circle having its center at the center of the enemy's alignment, when, an extreme ship
{figure}
FIG. 37
being taken as the regulator, every ship is in a position such that the angle between the line joining it with the adjacent ship in the direction of the regulator and the line joining it with the afore-said enemy's center, is 90°.
Supposing the ships to be on such an alignment, we propose to study the maneuvering that permits of maintaining it.
Let us consider two adjacent ships A and A' (Fig. 37) of an alignment at positions equidistant from NO, having as a radius the distance r; the angle AA'NO being 90°. Let us indicate by d the distance AA' and by the angle ANOA'; we then have
sin a = d/r
Let a and a' be the polar bearings on which, at the instant under consideration, the respective ships A and A' hold NO; these bearings being counted from the bow. If ? is the polar bearing on which A is held by N (counted from the stern), the analogous bearing for A' could be ? +E or ? —c. We will indicate by V,V' and VN the respective speeds of A, A' and NO.
Let us note first of all that if there exists the relations
V sin a= VN sin ?,
the indicator of movement of A with respect to NO is given by the joining line ANO; and hence, in order to preserve the alignment in the fundamental position, the ship A' (and, more in general, the ships of the alignment opposed to NO) must keep the course and speed of A.
While not excluding the possibility that the conditions just mentioned may be realized in practice, it is readily seen that this method with uniform speed and course cannot be held to be general, because it is not logical to establish the aforesaid relation as a necessary condition; let us, however, seek to determine the criteria for maneuvering at equidistant positions in a way that may permit the maximum freedom of execution. Let us see if it is acceptable to carry out the maneuvering by the two following methods:
1st. At uniform speed; that is to say, with the ships A and A' maneuvering at the same speed V which, in general, naturally requires different sight-vane angles a and a'.
2d. With a uniform sight-vane angle, which ordinarily requires that the ships A and A' have different speeds V and V'.
In both cases the ships of the A party must move in such a way that, in the time dt, they may have the same change dr in the distance from NO. If we wished to calculate the unknown values a' and V' it would then suffice to apply the fundamental tactical relation. Thus, for the method at a uniform speed, we have
VN cos ? —V cos a=VN cos (? ±a)—V cos a'. (1)
Naturally, when the value of cos a' supplied by this formula is not, in absolute value, less than unity, it means that the method is not applicable.
For the other method, in the foregoing relation it would be necessary to put V' cos a in place of V cos a'; in other words, we may say that the value of V' must satisfy the condition
V' cos a= V cos a', (2)
where in it is necessary to introduce the value of cos a' obtained from (1).
Applying these methods, evidently the distance AA' does not remain invariable.
In order to fix these ideas, let us consider the simplest hypothesis, which is that of a stationary enemy. Putting, in formula (I), VN=o, we have a'=a; which, introduced into formula (2), gives V'=V; hence, in the particular case to which we now refer, the two methods just mentioned are combined, the ships being able to maneuver with uniform speed and sight-vane angle. Against a low fort, or a ship at anchor, such maneuvering may be opportune, because it permits the ships of a homogeneous division to keep the enemy bearing in a direction of maximum utilization.
We may, then, in a very simple way, extend the rules established for maneuvering an isolated ship to the maneuvering of a division; because such rules, in the case of a stationary enemy, evidently lead to maneuvering at a limited distance, keeping the enemy bearing in directions of maximum utilization alternately forward of and abaft the beam.
In such case the joining lines ANO and A'NO both revolve through the same angle, because formula (10) of Chapter I (section 37), becomes
d?/dt = V sin a/r.
The angle ? under which the ships A and A' are seen from NO thus remains invariable; therefore, when the radius of the equidistant alignment passes from a value r1 to a value r2, the distance AA' changes from a valued d1 to d2; and there is realized
d1/r1 = d2/r2 ;
both the members of the equation being equal to sin ?. Consequently, if r1 and r2 are respectively the superior and inferior limits between which it is predetermined to maintain the distance from the enemy NO, when the maneuvering is begun at the superior limit of the fighting distance it is necessary that the distance d1 between ships be established as somewhat greater than the allowable minimum, remembering that during the maneuvering it will be reduced to d2. When, as generally happens, the ratio r2/r1 is not inferior to 7/10, it might seem opportune to establish for d1 the value that is ordinarily assumed as the normal; and this in conformity with what is said in the preceding chapter concerning the diminution of the distance allowable during the evolutions. It is clear, however, that in every tactical maneuver this tolerance may obtain within narrower limits; thus, in the special case that we are considering, it is necessary to remember that, at the instant at which the ships find themselves at the minimum distance, they must execute a simultaneous change of course in order to bring the enemy to bear abaft the beam; it is, therefore, well to establish that the normal distance between ships shall be realized for the mean distance r1 + r2/2 from the enemy, rather than for the maximum distance r1.
For example, supposing the limits between which it is desired to keep the firing distance to be 10,000 meters and 7000 meters, and the normal distance between ships to be 500 meters; to the end that the latter may correspond to the mean distance (8500 meters) from the enemy, it is necessary for the ships, when they begin the action at the distance of 10,000 meters, to have an interval between them of 600 meters; and, by reason of the maneuvering, at the limit of the approach it will be 400 meters; which will always be sufficient.
Such an amount of oscillation (100 meters more or less than the normal distance) is allowable even against an enemy's fleet in motion; and in fact it is well to observe: 1st. That, theoretically, every increase in length of the alignment constitutes a disadvantage of position; however, as we have already observed in Chapter III of Part I, if the difference in length between two opposing alignments is 500 or 1000 meters, it may be held to be negligible in practice, because only a small part of it affects the conditions of position. 2d. The normal distance between ships must of necessity be established as somewhat greater than the minimum which confers safety of maneuvering.
Without doubt, then, we may affirm that, having regard to maneuvering at equidistant positions in the general case of an adversary in motion, it is well to be governed by the following rules: 1st, watch the variations of the distance between ships, with the understanding that these variations are to be kept within sufficiently narrow limits; 2d, it is well that the distance between ships at the limit of offensive contact should be somewhat greater than the normal.
This being established, we make the following reflections:
The method at uniform speed is naturally that which at first sight appears to be preferable; but it may possibly lead to varying the distance between ships beyond the desired limits. On the other hand, the method with a uniform sight-vane angle might require a ratio V’/V differing too much from unity.
Let us note that, for the maneuver in question, the ship A', in order to keep the speed V, should keep NO bearing at an angle a’ while the polar bearing a would correspond to the speed V'; hence, to a bearing a1 intermediate between a and a', there will correspond a speed V1, intermediate between V and V'; or, the ration V1/V will be nearer to unity than V’/V.
We recall further that, while the ship NO – from which it is desired to keep the ships of the alignment at equidistant positions —is the one that occupies a central position in the enemy's alignment, the ship upon which ordinarily it is best to concentrate the offense, is an extreme ship of the said alignment. It results from this that the extreme ship of our own alignment, which serves as a regulator, must keep the enemy's ship for the concentration of fire at an opportune sight-vane angle which will be established according to criteria of which we will shortly speak; the polar bearing of NO will be the one which will derive as a consequence of this. If, thus far, we have referred to the polar bearing of NO it has only been for the sake of simplicity of reasoning.
The criteria sought for the execution if the maneuvering at equidistant positions may be established in the following manner. Let us suppose our alignment to be in the fundamental position, and that the ships have all the same course, so that they are on a line of polar bearing. An extreme ship, taken as a regulator, keeps the enemy's ship for the concentration of fire on an opportune bearing, and, more in general, maneuvers, with respect to ale said enemy's ship, in a way conformable to the criteria determined upon in the study of the naval duel; thus describing, generally, a curvilinear track with a great radius of curvature.
Each ship continually imitates the movements of the adjacent ship in the direction of the regulator in such fashion as to keep itself in the position from which may result the angle of 900 between the line joining it with the said adjacent ship and the one joining it with the center of the enemy's alignment. With such object it may slightly modify its course with respect to the adjacent ship, but within a limit that does not produce too notable variations of distance. Such limit being reached, it is best for the said ship to vary the speed in order to preserve the desired position.
Briefly, it may be said that a ship must imitate the movements of the adjacent ship; that is, keep on a course about parallel to it, slightly modifying its course and speed in order to satisfy the 90° rule.
Thus the way to carry out the maneuvering at equidistant positions is by the fusion of the methods before alluded to. It is evidently well to ordain that the regulating ship be the inner one on the side of the changes of course necessary for steering by sight vane, and it is generally advisable for the said ship to maintain a speed slightly inferior to the normal speed,* to the end that the maneuvering may be facilitated for the other ships; or, in order to increase their reserve of speed. It is possible that the reserve of speed of the other ships may not be sufficient for maintaining the alignment in fundamental position; nevertheless, it is easy to see that the most rational criterion for maneuvering remains as above mentioned; indeed, in such case, although not fully attaining the object of keeping the alignment in fundamental position, we approximate to it as nearly as possible.
If the regulator ship develops the maximum speed, the application of the prescribed rule causes the ships to change course in a continuous way parallel to it; and the formation becomes a line of polar bearing, in which, however, the bearing may be slowly variable, the ships executing continuous but very slow changes of course with a great radius.
* As has been said in the preceding chapter (section 49), the normal speed is inferior to the evolutionary speed which is generally the maximum speed of the slowest unit. When the alignment is changed by wheeling the column of vessels, it is necessary for the pivot ship to reduce its speed to one-half of the evolutionary speed; but, in the case of maneuvering at equidistant positions, the reduction of the speed of the regulator ship must be kept within restricted limits, enabling the speed to be maintained. In like manner to that of limiting the reductions from the maximum to a speed inferior by four or five knots—established for the naval duel— it is well to ordain that the speed of the regulator ship in the maneuvering under consideration shall not fall more than three knots below the normal speed. (Author's note.)
Let us now consider a composite rectilinear alignment; that is to say, two contiguous elementary alignments placed one on the prolongation of the other, or an angular alignment. It is clear that,in each elementary alignment, it must be sought to maneuver at positions equidistant from the enemy's corresponding alignment. One of the elementary alignments acts as a regulator; and the extreme ship of the other alignment, adjacent to the outer ship—with respect to the change of course—of the regulator alignment, imitates the movements of the latter, modifying its speed in the manner most opportune for the object that it is desired to secure.
From the foregoing we may conclude:
1st. The tactical maneuvering to be held as normal is that at equidistant positions; there results from it a flexible alignment, capable of being adapted in a continuous manner to the changeableness of the tactical situation, without disturbance to the firing.
2d. The said maneuvering admits, as a particular case, having a constant alignment, in which an extreme ship steers with the sight vane on an enemy's ship, and the others imitate its movements, tending to keep the courses parallel.
3d. The type of maneuvering just indicated presents no dangers, the inner ship on the side of the changes of course being chosen as the regulator, and the said changes being with a great radius resulting from steering by sight vane.
60. Inclination of the Ships to the Alignment.—Let us now see what conditions must be satisfied by the inclination of the ships to the alignment, to the end that it may be possible to concentrate the fire, while presenting the ships in the most opportune manner as regards offensive as well as defensive conditions.
Let N1 (Fig. 38) be the enemy's ship on which it is desired to concentrate the fire, and A1A2 an elementary alignment at positions equidistant from the center N0 of the enemy's alignment which, in the figure, is supposed to be in the fundamental position; but which, naturally, could also be inclined with respect to the line joining the centers.
For the determination with which we are now occupying ourselves we may hold that the various ships of A1A2 have about the same course. The ship. 41, which is at the extremity of the alignment nearest to N1, desires to bring that ship to bear in a limit direction of a sector of maximum offense; it might do this by haying its longitudinal axis* in the direction XX' or in the direction YY'; XX' and YY' being symmetrical with respect to N1A1.
It is clear, however, that, in the case of YY', the other ships of the alignment would have N1 bearing in a sector of minimum offense; while if the longitudinal axis of A, is in the direction XX', the other ships can have N, bearing in a direction inside of a sector of maximum offense. Naturally the bows of the party A must be in the direction A1X1 or in the direction A1X', according as A desires to bring the enemy to bear abaft or forward of the beam; hence it is well to reflect that, considering the sea plane to be divided into two parts by the alignment, the bow must be toward the side away from the enemy when he is to be brought to bear abaft the beam, and toward the side next to the enemy if he is to be brought to bear forward of the beam.
{figure}
FIG. 38
Let us now consider what may be the situation of the party A from a defensive point of view. In order to fix the idea, let us suppose that the party N is also in the fundamental position, but in column of vessels; and that the distance is 6000 meters.
The A party will possibly concentrate the fire on N1 or on N2; and if, as is customary, we refer to an alignment of six ships at intervals of 500 meters, the ship for concentration will receive the offense in a sector of about 25° couting from the beam.
This being the case, let us suppose that the ships of the A party have sectors of maximum offense with amplitudes of 45° forward of and abaft the beam; if N concentrates his fire upon A1, that ship will receive the offense in a sector included between directions
*In referring to the longitudinal axis we consider indifferently the hypothesis that N1 is kept forward of the beam, or that it is kept bearing abaft the beam. (Author's note.)
that form angles of from 20° to 45° with the longitudinal axis; if, however, the fire is concentrated upon A2, that ship receives the offense between directions that form angles of from 20° to 45° with the beam. This example suffices to show that it may be advantageous to present the ships inclined to the alignment; the more so as, within the limits of distance at which it is specially advisable to concentrate the fire (section 14), the angle A1N1A2 will have a value smaller than the one under consideration.
In case of the distribution of the fire it is seen a fortiori that it may be advantageous to present the ships inclined so that each ship may have its corresponding adversary bearing in a direction of maximum utilization.
It is to be noted that, when the A ships have sectors of maximum offense that extend 60° forward of and abaft the beam, if the regulator ship has N1 bearing in a limit direction of a sector of maximum offense—that is to say, only 30° from the longitudinal axis—it is possible that some ships will be exposed to enfilading fire; which presents no disadvantages at the maximum firing distances (as is said in Chapter I, Part I), but is ordinarily to be avoided. Hence it may generally be established that the polar bearing on which the regulator ship keeps the nearest enemy's ship by sight vane, must bear some relation to the way in which the enemy's alignment is inclined to the line joining the centers, as well as some relation to the criteria concerning the direction of maximum utilization.
61. Evolutions in Simple Alignment.—For offensive contact we have established the necessity of having as little recourse as possible to evolutions; without, however, excluding the possibility of being obliged to do so in case one cannot succeed in keeping the alignment in a position sufficiently near the fundamental position.
As has already been noted (section 58), the proper methods for changing the alignment are limited to that performed in succession and those based upon wheeling the column of vessels. In general, it is well to give the preference to the first method on account of its greater simplicity, and, owing to the possibility of changing an evolution in progress, adapting it to the counter movement of the enemy. It results from this that the other methods above mentioned can usefully be employed in particular cases, when it may be expected to secure with them the desired objects in a considerably shorter time than would be required by the evolution performed in succession; and this without too greatly disturbing the firing.
In executing the wheel with the speed ratio ½ conformably to the conclusions of section 33, IV, in order to have an advantage in rapidity over the evolution performed in succession, the angle to, through which it is desired to change the alignment, must be less than 30°, or than 60° according as the pivot is the rear ship or the leading ship. When pivoting on the ship about one-third from the head of the column—as results from the table in section 53—there is also an advantage in rapidity when WW reaches 90°.
From what has been said in this chapter, the ships will generally be inclined to the alignment. The evolution of section 53, II (which can be executed by pivoting on the rear ship or on the leading ship) permits of forming a column of vessels inclined at the angle ? to the actual alignment, without need of changing course together on the said actual alignment in order afterward to execute the wheel.
If the angle ? is within the limits above recorded, and if the course is sufficiently near the one required for the evolution, within a limit such as to permit one to expect but little disturbance to the firing, the evolution, pivoting-on the rear ship, is advisable if the course inclines toward the new alignment, or on the leading ship if the course inclines in the opposite direction. In other words, if a is the polar bearing of the formation, it is necessary that the difference ?c—a, or the other difference a-?t, be sufficiently small; ?c, and ?t indicating, as usual, the angles corresponding to ? given in the table for wheeling the column.
When the circumstances just mentioned are not realized, the course may be changed on the alignment, thus resulting in a column of vessels, and the wheel executed afterwards, pivoting at about one-third from the head of the column; in this way a gain in rapidity may be had, but the situation will often counsel its abandonment because the said advantage will be negligible when compared to the inconvenience resulting therefrom. The English writer several times cited expresses himself in this connection in the following manner: "Wheeling a column of vessels is undoubtedly an efficacious method of changing the direction of a long line in the quickest way possible; but reflecting upon the disorganization that such a change brings upon the firing of a squadron, it must be used with extreme caution."
Moreover, in prescribing the angle through which the alignment is to be changed by wheeling, it is necessary to keep in mind the probable counter-movement of the enemy; not taking this into account, there might be attributed to the methods by wheeling a greater importance than they really have; while, in practice, such importance is very limited.
We propose to fix these ideas by considering how such illusions may arise.
{figure}
FIG. 39
Let us suppose that the fleet A (Fig. 39) finds itself in the worst possible position; that is, the enemy N has succeeded in crossing the T, and that he has taken a course parallel and opposite to that of A with the object of maintaining his advantage of position and drawing the maximum profit there from by diminishing the distance. Let us indicate the speed of the A party by VA. If this party wheels his alignment through ?, pivoting on the rear vessel, the new inclination ? of A's alignment to the line joining the centers is greater than ?. We have already called attention to this in section 53 and observed that in contact out of range the difference ? – ? is of small importance; but it is understood that if the distance diminishes beyond a certain limit, the angle ? may become about 90°, ? still being within the limits before mentioned. Let us seek the conditions of distance necessary in order that we may have ?=90°.
Let S be the length of A's alignment, and let us, as usual, indicate by t, the duration of the wheel on the rear ship, and by t0 the length of time that would be required by an evolution in succession; that is to say, let
t0=S/VA.
If CA’ is the new position of A's center, and H is the initial position of the rear ship, since, during the evolution, the track of the pivot ship is ½VAt2, we obtain
HCA’=½VAt2+ ½S.
When there is realized the condition t2≤t0 (which by the table in section 33 corresponds to ?≤45°), we then have
HCA’≤S.
When ?≤45°, in the triangle HCA’ CN’ (in which CN’ indicates the position of N’s center simultaneous with the position CA’), we have
CA’ CN’≤HCA’,
or
CA’ CN’≤S.
In order that A may secure an advantage of position with in the limits established for WW for a wheel on the rear ship, it is necessary that the distance between the centers at the end of the evolution be less than the length of the alignment; and that the course of the party N be kept unchanged.
Given that the distance is within such limits as not to exclude the possibility that A may attain his object, if the party N answers by making a simultaneous change of course so as to move in the same direction in which A executes the wheel, thus bringing itself into column of vessels, the party A, at the end of the evolution, will find itself in a situation very different from the one imagined. In fact, setting aside for both the adversaries the time required for the changes of direction, let us suppose that N's change of direction is made at the same instant at which A begins the wheel; the party N, at the end of the time t2, would again be in fundamental position when its center should arrive at a point M, such that CNMCA’=90°. Now, drawing CA’R parallel to CN’M, from the right-angled triangle CA’RH, which is right angled at R, we have
RCA’= CNM = HCA’ sin ?
As has already been noted, to ?=45°, there would correspond t2=t0 and HCA’=S; in such case we should have
CNM=S sin 45° =0.7S,
and hence the speed VN necessary to allow CN to arrive at M when the center A reaches CA’ would be given by
VNt0=0.7S
or
VN=0.7VA
When ?<45° a smaller value of VN than this would be sufficient; this shows that, although the counter-move of N may not be immediate, if the party N possesses a speed about equal to that of the enemy, this speed will be sufficient to permit CN to arrive on the line CA’M and even to pass beyond it. So, then, at the end of the above mentioned wheel the party A might be in a relative position so different from the one prognosticated as to render another evolution necessary. In order not to run such risk the amplitude ? of the wheel should evidently be 900, and the pivot should be on the ship at one-third from the head of the column. But it is also well to reflect that, besides the evolutionary rapidity, it is important, as regards the advantages of position, not to change the alignment any more than is necessary; for this reason, everything considered, it seems that in the case in question the evolution performed in succession would be preferable for A, unless the extreme ships are very swift.
As is well known, in simultaneous changes of direction, every ship must wait for the movement to be begun by the adjacent inner ship on the side toward which the change is made; for this reason the changes of direction that are called simultaneous are practically successive changes at very short intervals of time. Conformably to this, in order to execute such changes with the maximum promptness, it is to be borne in mind that the inner ship on the side toward which the change is made can haul down the signal and begin the movement as soon as the signal is repeated by the adjacent ship.
A particular case worthy of consideration is that of a fleet in column of vessels that desires rapidly to invert the course. It is not impossible that this may be required in order to stop an abrupt movement of the enemy, as happened to the Japanese at the battle of Tsushima. In such case the simultaneous change of direction would contemporaneously disorganize the firing of the whole fleet; therefore, the example of Togo is to be imitated by making the ships of each division change together, and the divisions change in succession so that, during the movement, one division remains protecting the other with its fire.
62. T Positions.—To the criteria established for the conduct of a fleet in a simple alignment in offensive contact it is well to add a few observations directly regarding the object that the maneuver must have in view.
I. It is incontrovertible that the ideal object would be that of crossing the T; but with two compact fleets it is obvious that this cannot be accomplished, no matter how small the maneuvering qualities of the enemy may be. Therefore, it is not necessary to sacrifice the maneuvering in the least in order to tend toward this ideal. The immediate tactical situation must be kept in view, seeking above everything else to maintain oneself in fundamental position while still tending toward crossing the T. Very small importance should then be attributed to the study of maneuvers based upon a preconception of passive conduct on the part of the enemy. Let us give an example of this.
Supposing two adversaries in column of vessels, if one of them keeps the course unchanged, then the other, possessing greater speed and his column leader steering with a certain sight-vane angle, can reach a sector of minimum offense of the enemy's fleet. Given the speed ratio and the limits within which it is desired to keep the variation of the distance, the opportune sight-vane angle might be graphically deduced and the various angles afterwards registered in a table, the practical importance of which we may value with the following consideration.
It is not impossible that, by concentrating the fire on the leading ship of the enemy's line, we may deprive the said line of its chief; for this it would be necessary that the flagship initially lead the line; that, the commander-in-chief being dead, the signal transferring the command be not seen; and that the commander of the leading ship, being without orders, should keep the course unchanged, as happened at the battle of August 10, 1904. But this is a very particular case, and it is logical to believe that the enemy will so act as to avoid it, considering this hypothesis to be among those generally prescribed for tactical contact. Then, the maneuvering commenced with the sight-vane angle supplied by the table would not answer to any rational conception; rather, it is easy to believe that the table would be a useless shackle, even in case the enemy should behave in the aforesaid passive manner, because, the maneuvers inspired by the criteria generally admitted in the preceding sections would answer better.
II. From what has been said in the preceding chapter (section 56), it is to be predicted that, at the beginning of offensive contact, the positions of the two adversaries will not be tactically equivalent; it is even not illogical to affirm that, while generally excluding the probability—as has just been observed—that the ideal crossing of the T may be completely secured, it will beat the initial moment that it will be possible to approach that ideal.
In order to fix the idea, let us note that, at Tsushima, the fleet of Togo, finding itself forward of the enemy's beam at the moment of sighting him, if it had steered on a line of bearing directly on the course of the latter, it would presumably have been able to establish offensive contact in a more predominant position than the one obtained with the inclined course and with the formation in column of vessels.
So, then, the example of the preceding section shows that if one of the adversaries is in an advantageous position, the evolution of the enemy intended to establish superiority or at least tactical equivalence, will hardly completely attain its object, it being very easy to execute the counter-movement to such an evolution; on the contrary, if instead of supposing—as in the said example— that the party N, after having crossed the T, has taken a course parallel to that of A, we imagine that it maneuvers according to the criteria deduced in section 59, the counter-movement to A's evolution might not always be necessary. In such case it is true that A might succeed in assuming an equivalent alignment; nevertheless, even when this is reached, the ships of A, being in column of vessels, will not find themselves in the best defensive conditions, and it will still remain to them to execute a simultaneous change of direction, with disturbance to the firing, in order effectively to establish conditions of equivalence; while the ships of N will have been all the time in the best possible conditions from the offensive and defensive points of view. For this reason, and on account of the difficulty of properly estimating the variability of the tactical situation during the evolution, it is to be presumed that some portion of an advantage of position will always remain; and if we bear in mind, as already noted in section 25, that the advantages obtained produce a compound effect, that victory is the integration of small advantages, each one of which, separately considered, might seem negligible, we must recognize the great importance to be attributed to the initial tactical situation.
III. Having had the good fortune to cross the T, in order to maintain the relative position with respect to the enemy, it is necessary to change to a parallel course; but it seems logical to limit this rule to cases in which its application does not imply a sacrifice of offensive power. In fact it is not presumable that the enemy will not maneuver to extricate himself from his critical position, and hence, proposing to one self the object of maintaining the position with a sacrifice of offensive power, although the latter may prove to be all sufficient, would seem to be aiming at an illusory object, to obtain which one will find himself obliged to execute two changes of course at very short intervals of time. Thus, having crossed the T with respect to a fleet in column of vessels, if one were to change his course, one-half of his principal armament would quickly go out of action. Let us suppose further that in this way one might remain in the advantageous position for a time double that which would remain to him when developing the maximum offensive power; the minor duration of the advantage would be compensated in the second case by the greater total result. For the rest, under the wild hypothesis that the enemy does not maneuver, one might keep himself in the sector of minimum offense of the enemy's alignment, still developing the maximum intensity of fire; indeed, it would suffice to execute an opportune change of course on arriving in proximity to the limit of the aforesaid sector.
63. Maneuvering on a Double Alignment.—It is well known that the experiments carried out in France with the already mentioned Fournier system of tactics, have brought to light the inconveniences of the double alignment in offensive contact.
The illustrious admiral proposed to himself, by dividing the fleet into tactical units each formed by three ships, to obtain great manageability by virtue of the shortening of the line. For this purpose, the group-leading ships, as well as the units composing such groups, must not be held rigidly bound to the formation, but must move opportunely on their own initiative in order to secure the best utilization of the guns. Nevertheless, in practice, the ships of the outer line, obliged to fire at targets that present themselves between friendly ships, cannot always be in the desired position; frequent changes of the target constitute the inevitable inconvenience of the double alignment.
On the other hand, in the preceding chapter (section 55),it has been made evident that such a form of alignment has scant evolutionary capacity; or, the manageability deriving from the shortening of the line is only apparent. In order to tend toward this object it might be prescribed that the distance between ships could be shorter than that held to be necessary for the simple alignment; but there would then result a limitation of the movements, it being necessary to abandon simultaneous changes of course; and the anxieties of maneuvering would be increased.
Finally, as we have already noted in Chapter II of Part I (section 11), the launching of torpedoes for the maximum run against a fleet, while it is not rational if the enemy's alignment is a simple one, may have a probability of success against a fleet in two lines.
For these reasons we hold that, unless we have a very numerous fleet, the adoption of the double alignment is to be restricted to cases in which we ought to utilize in the second line any antiquated ships, limiting their number, however, as is set down in section 56.
64. Maneuvering by Independent Groups.—Let us suppose a fleet broken up into groups each one of which has a speed not inferior to that of the enemy's fleet; that is to say, the condition recognized in section 57 as necessary for obtaining a good initial situation is satisfied.
It is true, as we noted in section 20, that the compact fleet, by assuming an opportune angular alignment, may bring itself into conditions of equivalence with respect to the enemy that is divided into groups; it is obvious, however, that, in practice, it will not succeed in obtaining these conditions continuously, because the divisions of the compact fleet cannot always satisfy the double condition of keeping together, and having, each one of them, an alignment in fundamental position with respect to the corresponding group of the enemy, besides having the ships in dined to the alignment in a way suitable for the development of the maximum offensive power. The tactical government of the compact fleet will have to satisfy too many conditions, owing to which the said compact fleet will be notably a poorer maneuverer than the enemy.
The advantage of maneuvering by groups being derived from this idea, it is clear that such advantage will be maximum when one of the groups is composed of a few ships(not more than six) endowed with very high speed. The maneuvering of this division, called the flying squadron, must be developed in a way such as to produce the maximum rapidity of rotation of the line joining it with the adversary; then it is to be presumed that it can enter a sector of maximum offense.
The number of ships of the flying squadron having to be limited, as has just been said, it appears to be clear that it is important that each of these ships should have a powerful armament. The type adapted to such a purpose is then that of a very swift armored ship, with a speed of at least four or five knots greater than the types that are constructed for composing the principal squadrons, with a powerful armament, and with the best protection possible subordinately to the development of the offensive capacity and the mobility.
From what has already been established, the flying squadron must generally be kept at the same distance from the enemy as the principal squadron; but when the distance falls near to the lower limit of the mean distance (3500 meters) a closing in maneuver by the flying squadron is not to be deemed rash, trusting that if the enemy commits the error of maneuvering to engage with the said group, he will place himself in conditions of inferiority with the opposing principal squadron. If, on the other hand, this were attempted at a greater distance, given the time that would be required for a considerable approach, the flying squadron would risk being overpowered.
Conformably to what we have set forth in section 62, III, the flying squadron must not sacrifice the development of the maximum offensive power to the maintenance of a T position.
65. Maneuvering at Close Quarters.—We now propose to see how the criteria established in section 46 for the maneuvering of a single ship within the limits of a fight at close quarters may be extended to a fleet of ships. Even if, as is to be presumed, the two adversaries do not maneuver with the principal object of ramming, they must run to meet each other.
For convenience of reasoning, let us begin by considering the hypothesis that a group composed of several ships is fighting an isolated ship; and let us ask ourselves the following question: Given that the ships of the group desire to ram the enemy's ship, what could be the formation and the most opportune maneuver?
Let us observe that it would be exceedingly dangerous for the ships of the group to execute a maneuver which might have for its object the concentration of the rams; we mean by this that if, for example, the ships of the group are two, A and B, disposed in line abreast, and if the enemy's ship C steers for the center of their formation, the two ships A and B cannot attempt simultaneously to ram C without risking ramming each other. In other words, A, for example, can head for C, and B must change course parallel to A; while C, insofar as the ram is concerned, will in this way have to do with but one ship.
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FIG. 40
This simple fact must be kept in mind because it shows that any maneuver based upon the concentration of the rams must be abandoned; and that, instead, for the employment of these weapons, it is necessary to base it on successive action. In order that the action may assume this second form, the formation of the group must needs be a deep one; consequently the column of vessels may be considered as the fundamental position.
The column leader of the group steers for the enemy's ship; the two ships pass close to each other; the second ship in the line maneuvers with respect to the enemy without troubling itself to fallow the column leader in succession, and so on.
It is here necessary to observe that the conditions of the ship that fights with the group grow worse the greater is the depth of the latter's formation, up to a certain limit. With this we desire to refer, not only to the greater number of ships that successively attempt to ram, but also to the offensive returns of the same. Since, indeed, within the limit of their close approach, each ship has the maximum interest in keeping the bow on the enemy, the ship A (Fig. 40), after passing C, turns with the helm hard over so as to come again to a meeting with C; and, analogously, C would wish to turn also, but cannot do soon account of B, who imitates the maneuver performed by A. The ship C is hence prevented from inverting the course, and consequently finds itself in a condition of grave inferiority with respect to A, unless it has more speed or possesses better evolutionary qualities. The group is so much the better disposed for this purpose the more the depth of its formation approaches that necessary forgiving A a notable advantage with respect to C in the inversion of the course. It is understood that in increasing the depth of formation beyond a certain limit, the advantage ceases to exist.
Passing from the particular case considered to the more general one of two groups on the basis of the ram only, it results from this that a group that moves in line abreast against another in a formation nearly approaching that of a column of vessels, is in an inferior position; it suffices that the ships of the latter group be not bound to maintain the formation, but may consider it only as a basis for the maneuvering.
Let us now see what conclusions may be reached in relation to the employment of the torpedo. We begin as usual with considering the hypothesis of a group of ships that attack a single enemy's ship; both the adversaries are supposed to be armed with lateral launching tubes.
It is easily seen that the group must do its best to have its own ships pass successively on the same side of the enemy. As a matter of fact, if the group is composed of two ships, it will be able to use its torpedoes as well if the enemy's ship passes between the ships of the group, as if it leaves them both on the same hand; but in the first case (which is that in which the ships of the group are not in Column of vessels) the group permits the enemy to put forth his maximum offense by launching torpedoes from both sides. For this reason it is obvious that the first method of action is preferable, even when the ships of the group are more than two.
At this point the object of the maneuvering of the group appears to be thus determined: To pass by on the same side of the enemy's ship. The maneuvers should then be about that in column of vessels and in succession. Inversely, the ship that fights the aforesaid group should maneuver so as to pass between the ships of that, group.
Let us now suppose the two groups to be equally armed with torpedoes, and let us imagine that the first has a front formation, and the other a, deep formation. For example, let four be the number of ships composing each group, and let us indicate by A, B, C, D (Fig. 41) the ships of the first group, and by A1, B1, C1, D1, those of the second.
If, in order to consider a special hypothesis, we imagine the first group to be formed in a square and the second in column of vessels, as shown in the figure, it is evident that, as regards the torpedo, the group A1, B1, C1, D1, during the passage by, will be in better conditions' than the other, because it can fire twice the number of torpedoes.
As the same reasoning might be repeated for formations analogous to those considered, we may affirm that the object of the maneuver in battle at close quarters, must, with regard to the use of the torpedo, be that of obliging the enemy's ships always to present the same side in passing by; and inversely, each ship, bearing in mind the object just mentioned, must seek to pass between the enemy’s ships so as to launch the greater number of torpedoes.
It results from the foregoing that the maneuver for the employment of the torpedo in battle at close quarters harmonizes with what is necessary for the possibility of ramming.
Let us now place what we have set forth in its relation to the employment of the guns.
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FIG. 41
It being admitted that, within a certain limit of distance, the adversaries must steer for each other, it is well to consider this necessity in connection with the other necessity of firing with the maximum number of guns permitted by the development of the action; consequently, while in long-range battle, a ship has to keep the enemy bearing in a sector of maximum offense, inside of the aforesaid limit it would be in a position which permits of firing in the direction of the bow. Not only does the line abreast satisfy this condition, but also any other formation in a straight or curved line which permits the ships to fire ahead.
Summing up, we may note that, considering the three weapons together, the best arrangement for the ships in battle at close quarters is that which permits the simultaneous employment of the forward guns, and differs as little as possible from the column of vessels; in other words, it is a question of a line of bearing that makes a small angle with the direction of the course.
In steering for battle at close quarters the ships of each group must hence take, by prompt formation (any other method is evidently impossible), the aforesaid position with respect to the most advanced ship in the direction of the course; doubtless the distance between ships will not be the same, and, in fact, the formation will differ in practice from a line of bearing; but there is no need to trouble about that. In effect, it is sufficient for the ships to be echeloned on the side that possibly will be indicated by the admiral, or that the situation with respect to the enemy shows to be opportune.
Each ship of the group, after passing by the enemy, must naturally invert the course in order to run again upon him, unless it is prevented from making such a movement by the quick arrival at short distance of the enemy's ships. This inversion of the course presents no dangers of collision with friendly forces if the ships are sufficiently echeloned in depth and the opportune side is perfectly indicated, it being naturally the same toward which the leading ship has turned.
If the battle at close quarters, instead of taking place between two single groups, is general, according to the foregoing a party moves toward it with the single groups following each other, possibly toward the same part of the enemy, so as to obtain the concentration of forces.