In taking up a subject so fraught with the uncertainty of inexperience, both in peace and war, the natural misgivings of the writer urge him to beg for leniency to the following pages, both as to fact and fancy. The article has but one purpose and that is to create, if possible, discussion on both sides of this question of submarines. By thus bringing out new ideas and new speculations, on this somewhat undiscussed subject, our knowledge of the matter in hand is bound to be increased. In advance of extended experiment or actual warfare, this is the only method at our disposal. By so doing we may work out for ourselves new methods and improved means against this most insidious of all foes.
In its role of harbor-keeping vessel, the submarine has merely increased the impossibility of such a blockade as that of Admiral Sampson's at Santiago. However, now that we have wireless, a picket gives us any information that may be necessary as to an escaping enemy, and dispositions may be made to cut him off— perhaps as well as ever.
It is not the purpose of this article to reiterate that sea-power rests with sea-keeping ships. This truth has remained eternal, from the days of Themistocles to Togo. As long as submarines are harbor-keeping ships, they are auxiliaries.
If they should ever rise to the size of sea-keeping vessels, they must, perforce, lose largely in invisibility, and develop other qualities. Thus we have a new problem which we are yet hardly in a position to speculate upon.
The writer's knowledge of submarines is purely second-hand. Hence, any incorrect statements, regarding either them or their abilities, is made in the honesty of ignorance and the hope of correction. It is his sincere wish that, in the groping for more light, these statements may be torn to pieces by those who know, and that others may come to the rescue on his side, so that in the end, perhaps, there may be evolved a few fairly well indicated conditions, in this mode of warfare, that bring with them a consequent line of action on the part of him who has the submarine as an enemy.
QUALITIES OF SUBMARINES.
At the start it is well to bear in mind the chief qualities and characteristics of the craft in question. That is to say, such as they are, at their best, at the present day. These may be cited as follows:
1. Slow speed.
2. Great weight for internal capacity.
3. Inability to see or judge distances well, except in smooth water.
4. Sluggish in all movements—diving, turning, or answering engines.
5. Inability to allow for current, when running submerged.
6. Visibility of tower or periscope by day.
7. Vulnerability to gun-fire.
The one and only quality it has in its favor is invisibility. Its whole reason for being depends on this alone.
To make plainer the writer's views, let us touch briefly on these "handicaps," in the order named.
Slow Speed.—About 8 knots. This is always bound to be present in vessels of this type.
Great Weight, Etc.—This reduces their radius of action, by reducing their habitability, internal space for fuel and supplies, etc. To operate 50 miles from a base seems to be the present outside limit, especially under war conditions. Twenty-four hours' war habitability is about all these craft are now capable of.
Inability to See Well.—There is a difference of opinion, even among submarine officers themselves, on this point. Some claim to see everything, and others very little. The periscope certainly gets easily befogged, but there are ways of clearing it. With tower up, it is scarcely conceivable that a slow, sluggish sub can see to any successful purpose, in any kind of a chop or swell. Anyone who has looked out of a berth-deck air-port, with water washing across its face, can certainly form some idea of how little can be seen from the water-level, in a submarine's conning- tower. How much more would the difficulty be increased in picking up a darkened ship at night.
Sluggish.—It is obvious what effect this quality would have upon a sub's ability to point her tube quickly at a given target, with the accuracy necessary for a successful shot with torpedoes or air-gun.
Steering Under Water.—By spinning an air-impulse gyroscope in any plane—say north—the submarine becomes independent of the compass. This is, as far as laying a course is concerned. But it does not take into consideration current, in a long run.
Visibility by Day.—A periscope or tower can be seen a fair distance by day. Five thousand yards away it would be plainly seen.
Vulnerability to Fire.—Experiments were, I understand, carried on in Manila Bay with a wooden dummy, which demonstrated this point. This was in a condition just submerged. It may be that high-explosive shell, bursting near a submarine with periscope up, would be sufficient to open her seams. This, however, is in the future.
With all these handicaps, it is seen that, after all, the only weapon of a sub is "invisibility."
How may she use it?
How shall we combat it?
These are the questions we should try to answer.
This essayist is of the opinion that "pickets," "keeping away," and "keeping dark" are among the best methods of overcoming the use of submarines by an enemy. The following is some attempt to show this.
SUBMARINES IN THE OFFENSE.
In common with other harbor-keeping ships, the natural role of submarines is the defense. There are, however, some—both lay and professional—who claim for the sub a position in the sea-fleet: their methods of operation seem to be the following:
1. When action is imminent, the subs are floated out of specially constructed vessels, or floated overboard from specially fitted transports, and take part in the action.
2. A fleet investing another fleet, and having a secondary base at hand, transports its subs thither, and operates from there.
One idea of those favoring this second method is, that the submarines will enter the harbor and destroy the shipping inside.
These two cases seem to comprise the whole of the offensive roles of the submarine. Let us glance at them consecutively.
In the first case, supposing that all mechanical features were overcome and that such launching, or hoisting out, were feasible, I think that we have but to go over the whole history of the rise and fall of portable torpedo boats, to class this phase of their use as impracticable. The submarines are slower and heavier than their predecessors. They must be hoisted out sealed up, and remain so, with their crews inside, etc., until they are hoisted in again—that is if they are ever found.
Supposing the approach of the enemy to be known by wireless, they must go overboard at least ten miles away in order to be ready in time. Their slow speed, however, prevents them from following the fight. They would be quite as likely to destroy friend as foe, if the fight came their way, owing to their poor seeing qualities. They could not fight in this fashion at night, and in daytime, even supposing they did get somewhere near the fight, they would have to expose themselves so much to see, that they would be a remarkably good target for gunfire. As Admiral Sir Cyprian Bridge says: "Submarines are nothing but handicapped torpedo boats."
The second method of using submarines in the offense is entirely feasible, if the base is near enough. That is, it is practicable as far as being able to operate the boats successfully is concerned.
However, attainment of the object sought is not so well indicated. It is scarcely conceivable that any enemy could not and would not secure its harbor mouth against the entrance of submarine boats. Even with a deep-water entrance, such as Newport possesses, if the submarine should elude scouts and work its way up the harbor unseen, lines of small electro-contact mines, and nets, strung across the mouth, and the entrance blocked up with cribs of stone to 40 feet ought to keep out any submarine. They could not see to lay countermines at night, totally submerged, and if they rose to place a countermine accurately, they would be undoubtedly seen and entangled or sunk by the pickets guarding the mine fields. Moreover, a mine exploded near them would probably start them leaking and sinking.
Another imaginable role for a submarine in the offense, is that of a picket, at night, for an investing fleet. They might get one of an escaping fleet, if they came their way, but their slow speed would allow the enemy to quickly get out of their range and radius of action. This is supposing that there was some way of their signaling to the main fleet.
We have here then the role of a submarine in the offense.
Is it worth anything?
SUBMARINES IN THE DEFENSE.
In their natural role they are a powerful menace, especially if they are in large numbers. In any naval investment they must be reckoned with, and reckoned with safely. No chances should be taken, especially with the battleships, in the vicinity of submarines, for the command of the sea must not be risked for the sake of remaining near a harbor entrance.
It is an interesting speculation this,—of what tactics a fleet or units of a fleet, would employ against the attack of submarines. Let us imagine a concrete case (Fig. 1). We have a harbor well defended by guns, etc. The coast line is at about 120°. The enemy's fleet is in port, having been driven off the seas. The harbor is well supplied with subs. Let us suppose the disposition of the investing fleet is as shown. There are pickets inshore with supporting cruisers (against destroyer attack). The battle-fleet with auxiliaries is well out to sea, say 25 miles.
In this case of our investing fleet opposed by a large number of subs, let us note the points we would wish to take up in order, perhaps, to arrive at some conclusions, in the subject under discussion.
1. Disposition of the fleet.
2. Pickets, and counter attacks by them upon subs.
3. Handling the fleet on being attacked.
4. Attack of submarines, singly and in numbers, by night and day.
5. Proposed maneuvers.
I. DISPOSITION OF THE FLEET.
Let us assume that the fleet is composed of eight battleships and the numbers and types corresponding to a main body of this size. Their disposition is shown in Fig. 1.
At twenty-five miles the fleet is in a position to handle any escaping vessels. The auxiliaries are placed as convenience and safety dictate. This last, of course, supposes there is no secondary base at hand. In this unlikely event, it would be well nigh impossible to keep up a continuous investment. However, that is not the subject under discussion.
The battle-fleet is picketed by the destroyers in reserve for the day. The destroyers off duty are with the auxiliaries.
The destroyers on duty are patrolling near the entrance, between the fleet and shore for any visible signs of submarines.
The supporting cruisers patrol a beat, changing their position frequently so that no under-water run can locate them sufficiently well for a successful shot. If submarines should make an attack upon them under the disconcerting circumstances of a coincident destroyer attack, the cruisers make off at an i8-knot gait, get well clear of the subs, and dispose of the destroyers that have followed them, at leisure. This is just one example of the speed-handicap of a submarine.
During daylight the pickets can see any subs awash or their periscopes. If, however, they eluded the pickets and patrols by deep under-water runs of 25 miles (3 hours), they would have to rise to get some sort of bearings of the battle-fleet, moving in a direction unknown to them, and would then be seen by the pickets. The mere fact of being seen would then spoil their attack. All the large ships would at once make off, leaving the subs, that had already made a long run, to the nets and gunfire of the destroyers. They would have a fair chance of bagging some of them, surely. Especially before they got back to harbor.
Thus, then, it may be said that a submarine attack upon a well-picketed fleet, lying at a distance from their base, has practically no chance by day.
At night, however, it is a different story. A night attack has great chances of success, if the submarines can only get near their target. To do this they must have speed and seeing power.
Then, under the most favorable circumstances, they may probably get in as many hits as a destroyer would, similarly placed.
To combat this likelihood of night attack, the fleet moves to a safe distance—say fifty miles. This is two and a half hours at ten knots from their day position (Fig. 2). The fleet cruises outside this radius all night. This is on the understanding that there is no secondary base. If there is such a base the fleet simply secures itself there from submarine attack.
This radius of fifty miles is taken on the assumption of the present best conditions of the submarine, i. e., speed eight knots, and forty miles submerged run.
A submarine might reach this radius in one of two ways; She may run out five hours submerged in daylight, wait for dark, and do the rest of her running awash (in which case her tower-wave is very visible); or, she can wait for dark, run submerged past the pickets, then awash until near the fifty-mile radius, when she can submerge with periscope only showing, and then be ready for business. Observe that it is said "reach the fifty-mile radius." This does not mean picking up the fleet. That is a more difficult job. In fact, as will be shown later, the chances are much against her picking up the fleet, even if one of a large fleet of submarines. Attacking, at night, on this radius, will always mean returning awash, with liability to capture by patrols and pickets, with no means of offense.
Operating at this distance is, at best, a precarious thing for subs, with their helplessness in cases of accident, and their other handicaps. But there is no reason the distance cannot be increased to seventy miles. At this distance there appears to be greater safety from submarines than from ordinary accidents.
The action of pickets, during darkness, would seem to be to move up nearer the entrance, out of search-light range, ready to fire upon or entangle any submarine they might chance upon. This is not altogether so improbable, if we remember that subs moving with tower or periscope up make a visible wave, if going at any speed.
Moreover, one good shot is more than likely to sink them. Unless the water allows them to run deep, it is well within the law of chances that one or more may blunder into the nets of a pair of pickets. However, at night the indications are that they are not very liable to capture. We will proceed on this assumption.
If the battle-fleet pickets are sent in just before daylight to patrol the sea between the harbor and the fleet, it is quite possible that they may pick up some subs, that, having failed to pick up the fleet during the night, are returning, perforce, on the surface or awash.
The sum and substance, then, of the presented scheme for immunity from submarine attack, is to keep well picketed and outside their radius of action.
2. PICKETS.
Pickets are the eyes and tentacles of the fleet. Nowhere are they of greater value than in the presence of submarines.
The mere knowledge that submarines are in the immediate vicinity is almost safety in itself.
That there must be enough of these pickets, and that they must be of a proper type, is self-evident. As far as type goes, the destroyer seems to fulfill the necessary conditions (as far as we know at present). They are fast and draw somewhat less than ten feet. Hence they are safe for the usual set depth of torpedoes and mines. It is scarcely probable that a discovered (and hence disarmed) submarine would waste a shot on a picket. Destroyers are quick and hard to hit. A smaller type would not be sea-keeping.
However, thought, experience, and maneuvers, should determine the type, and also the number.
In determining the number, in any building scheme, of the pickets per battleship, it should only be done with a large factor of safety for breakdowns, strain on personnel, losses, etc. No more than one day's duty on the inner line every third day ought to be required, with the next day at the depot ship, for sleep, stores, and tinkering machinery. For every fleet of eight battleships, then, three flotillas, of ten each, seem none too few.
Not only for this work of pickets are they good, but they have their own role. Also, at sea they are excellent scouts.
Of course they should be fitted with wireless.
The total "sea-army" of an eight-battleship fleet is a considerable number of ships, and as "sea-pickets" (not scouts) they are no more than sufficient for such a large number of vessels.
Pickets are as necessary for a sea-army as a "land-army." Posted 4000 yards outside the main body, they could see, in daylight, everything at least two miles outside of them. Two miles is fifteen minutes for a sub. Between them and the main body the eye could pick up easily any suspicious swash, tower or periscope.
At night, in the hope of perhaps seeing the "bone" of a sub moving quickly, they could be better stationed at i000 yards.
This then is their role simply as lookouts.
Now then, in discovering the proximity of subs, what offensive action would the pickets take, both by night and by day. Their action by day would undoubtedly be to move closer and shoot. The English have attacked successfully by pairs of subs dragging a net between them, and entangling them, or pulling their periscope over. Gunfire ought to be effective, however, if any part of them is exposed for as much as a minute. And this is probable, for the subs must get some kind of bearings of their target, if they wish to hit.
As regards the ability of pickets to keep submarines from coming out of a harbor, one method of speculation is as follows: The pickets run strings of small electro-contact mines across the channel mouth. These are picked up in the morning if they have not been countermined during the night. Or, as this would be difficult under the guns of the forts, they might be simply left there. They could be small, cheap, and light. Just sufficient to stave in a submarine.
3. HANDLING OF THE FLEET IN A SUBMARINE ATTACK.
On the pickets discovering the submarines, what would be the handling of the fleet?
The direction of the danger being immediately known, one method of action is to turn the vessel's stern towards the subs, and steam rapidly away. The stern presents a small (although vital) target, and this method has the advantage of quickly getting out of range, and of giving the screw race for the torpedo to run through.
If the fleet went off only at the modest speed of ten knots, a thirty-knot torpedo (extreme range 3000 yards) discharged at 2000 yards would be at the end of its run when it reached the fleeing target. This assumes that the time to turn to run, and the time to take bearings for the shot are about equal. More than this, the screw race probably would throw it off its course.
In addition to the tactics of the fleet, firing would be going on from the secondary batteries of the fleet and pickets. For the subs to get in a shot they would have to get a bearing. To get a bearing, something must show above water, and this something would be a target for the gunfire of everything at hand.
This is by day. We may then formulate a rule that, on discovering a submarine, a large vessel should turn tail and open fire.
For night, too, this holds good. In this case, however, it might be wise to keep one course for only fifteen minutes. A thousand yards will then have been gained on the subs (speeds eight and ten knots) and the fleet will have moved 2.5 miles away. This change of course might clear a line of submarines lying in wait, expecting the fleet to be driven towards it.
In any event it is essential to avoid panic, and move together on prearranged, and well-understood signals, leaving active measures against the subs to the pickets.
In addition to the above there is nothing so essential as to keep dark. This will be dilated upon later. There is nothing so valuable to a sub as a guiding light of any description.
4. ATTACKS OF SUBMARINES—SINGLY AND IN NUMBERS—BY DAY AND NIGHT.
It is now time to speculate on the other side of the question, trying to imagine how we may be attacked and then how we may prevent it. Let us see how a submarine may be handled for the attack.
First, let us remember her infirmities—slow speed, sluggish, poor seeing qualities, etc. Rough weather increases the difficulty of seeing. Judging distances by periscope is difficult. As before stated, at any good speed the periscope or tower makes a big white "bone" easily seen, even at night, for some distance. All these must be allowed for or overcome in any mode of attack. It must be remembered that invisibility by day can only be obtained by complete submersion, and with this, in long runs, current cannot be allowed for. The sub must rise, under these circumstances, before delivering a blow.
Take the concrete case of a single sub attacking a single ship. She sees smoke on the horizon, or the faint outlines of a ship. Laying a course she dives and approaches for a distance which she calculates will bring her near her mark (Fig. 3).
To do this she must calculate the speed of the vessel and her course. At such a distance, and so close to the water, this calculation is more in the nature of a wild guess than anything else. Say the first distance is 5000 yards. She never could get this near in reality without being seen, but this makes the following calculation all in the sub's favor.
The speed of E (enemy) is twelve knots. Speed of S (sub) is eight knots. S must lay a course so as to get within torpedo range (2000 yards). Owing to S's slow speed the case is impossible unless E is steering a course somewhere in the angle AEB.
Suppose, however, she is steering inside this angle—say EO. This is a mean course. The sub dives (not having been seen) and calculates to rise near her and hit her unawares. Suppose S makes a miscalculatin of one knot in E's speed and of one point in her course. What error would this make on the position of S on rising?
An accurate calculation by S would put them both at 0 at the same time. Fig. 4 shows this error graphically. E is here going eleven instead twelve knots. She will arrive then at Q. The sub will at this moment rise at 0, distant about 760 yards from Q, and in plain sight. This error will more likely be moo yards, as a sub could not approach as close as 5000 yards by day.
The sub now having risen, E can turn tail (as per rule), or she can go off at right angles, where more of her guns will bear, and where it will be more difficult for S to hit. This last does not seem to possess so many advantages as the former.
So much for a single attack on a vessel or group of vessels. It emphasizes the fact that, once seen outside 2000 yards (and mostly inside, too) a slow sluggish submarine has no chance of success against any other class of vessel possessing a faster speed—say one-half more.
This is a day attack on a moving enemy. At night the attack is with conning-tower out. The attack is slow, to avoid the "bone." Supposing the subs, or fleet of subs, has blundered into the picketed battle fleet. They dive to get inside the i000-yard picket line, and then, if they can see their target, and if their target is not moving too fast, the chances are a successful torpedo shot.
But there are so many "if's." In the first place how far can a sub see a darkened ship at night? If she blundered into a fleet's picket line at night, the chances are by the time she dived to get inside, and got any where near, the fleet would have gone past. To show how little chance there is for a sub to pick up a fleet, at night, that is steaming outside of the fifty-mile radius, let us suppose that there are twenty submarines in the harbor our fleet is investing. The fleet at night is somewhere outside the fiftymile radius. The subs spread out fan-shape. At a radius of fifty miles they are five miles apart. If they travel in pairs, they are ten miles apart. They will pass a single ship a mean distance of a mile and a quarter, and a mile-long fleet (eight ships, double column, with allowances) at a mean distance of a mile. (Fig. 5). Ouery: Can a sub see a darkened vessel at a mile distant on an ordinary night?
Suppose she does. Can an eight-knot submarine catch anything? To blunder into a fleet at night unobserved, the sub must travel at some speed. To do that is apt to betray her presence to the pickets, and away go the fleet out of range, knowing that they are cruising in the dangerous zone, and, avoiding it thereafter, unless urgently needed there.
Of course if a sub did get in the middle of a fleet at night, it would be a nasty situation for the fleet, but not absolutely fatal to any ship. Luckily this unpleasant situation is a remote contingency with a fleet cruising outside the danger zone, and alert pickets ready to spot at once the white bone of a sub's conning-tower.
Let us imagine a general attack by the flotilla of submarines upon the investing fleet. They make a perfectly successful sortie (mechanically considered) from the harbor shown in Fig. 1. To avoid observation, they go out by day, traveling deep, and come to the surface at dark, waiting for the fleet to cross their track. This is at their maximum of thirty miles. (Assuming that forty miles is their total submerged run, and that they must have ten miles reserve.) At thirty miles the fleet, in double column, would pass at a mean distance of one-half to three-quarters of a mile.
This is on the assumption that the fleet does not start until dark, whereas it should be outside the danger zone at dark.
Darkness having come on, the sub moves out awash and slowly, so as not to betray her presence, and would take four hours to reach the fifty-mile radius. The sub has no guiding light, as, at the speed the fleet is moving, there is no flaming at the stacks or bow wave. Therefore, to fall in with the fleet, she must blunder into it, under the long chances already stated. Also she must catch them inside her danger angle (Fig. 3), if she is to get near enough to risk a shot. Now, if all these things happen just so (and, of course, they might, once in a great while), she has still to make a lucky shot at her target. For it must be noticed, that a mechanically perfect shot with a thirty-knot torpedo, fired at a target moving at right angles, at a distance of woo yards, has an error of 100 feet for every knot of error made in calculating the speed of the target. (Thirty-knot torpedo goes 1000 yards in a minute; ship moving one knot goes 100 feet in a minute.)
Now, in the danger angle the strongest part, structurally, of a vessel is presented, and the target is only from 8o to 125 feet wide.
It is a rare chance that will take in all these elements of uncertainty, and a submarine has to have all of them to bring her mission to a successful issue.
5. MANEUVERS.
The actual test of war is needed to thoroughly prove the truth or falsity of the foregoing statements. There are some of them, however, that we can very nearly get at by a systematic set of maneuvers. Up to the present time about all that has been shown with these boats is that a submarine is a submarine, i. e., can travel under water and reach a known fixed mark. The following set of maneuvers is suggested as a starter to attempt to try and establish what a sub can and cannot do, under conditions approximating as closely as possible to war.
1. A convoyed sub goes to sea in all sorts of weather. How far can she go totally submerged? What could she really do en route? What can she see?
2. Make a submarine dummy for a target. Anchor it so as to be detached at will, to simulate a sub rising to the surface for bearings. Have it fired at by a destroyer that does not know just where it is going to rise, for one minute. Note effect. Ranges 1000 to 2000 yards.
3. Attack of Sub by Day on an Unpicketed Vessel.—A twelve-knot vessel goes to sea and steams in a five-mile square (Fig. 6). A submarine endeavors to go to sea and torpedo her, using collapsible head torpedo. This ought to be carried on a great number of times.
4. Same Maneuver at Night.—Use three-mile square.
5. Effect of Wake on Torpedo Accuracy.—Vessel going ten to twelve knots. Fire a torpedo at her stern at different ranges to determine effect of screw wake on accuracy.
6. Visual Experiments.—In different weathers—by night and day, submarine goes to sea and endeavors to pick up vessel, all her lights being screened. Results tabulated. Experiments at same time from vessel as to how far, if at all, sub can be seen. As to what extent bow wave shows on sub at night and day.
7. Signal Drill by Fleet and Pickets.—Pickets signal "sub discovered" and direction. Vessels follow out plan in such an event.
8. Squadron Passes a Given Point at a Given Time at Night.—Speed is unknown to subs. Two subs take station to intercept the fleet and fire collapsible head torpedoes at vessels passing. This is to simulate the case of two subs blundering into a fleet cruising at the fifty-mile radius at night. The fleet is, of course, on the lookout for them, but does not know where they may meet them.
9. Same as the above except Position is only Approximately Known.—This simulates submarines having picked up a fleet, increasing their speed and trying to get within range. Problem is to see whether they can get past the pickets unseen and hit a vessel.
10. Day Attack of two Subs on a Fleet.—Speed of fleet five to six knots. Position not known within ten miles. Two or more subs attempt day attack. Note results as to sighting subs, and entangling of subs in nets by pickets, or opportunities pickets have for sinking subs by gunfire. Fleet maneuvers out of range, at once, on discovery of subs, and pickets engage in fight with subs.
These then are some maneuvers suggested, and it is hoped that something of the sort may soon be tried, so that our knowledge of the subject may be increased.
In concluding this speculative essay the writer begs to repeat what was said at the beginning in regard to its purpose.
A recapitulation of this subject of the submarine as an enemy, brings out strongly, according to the writer's views, the fact that the great handicaps of a submarine have not altogether been considered, in the more or less fanciful roles popularly assigned to it.
It is hoped that something in this direction has been proved. The sub is a slow, clumsy animal, but its bite is deadly. Keep out of its way, and at night don't betray your presence if you think any are about. In any event, they are not as apt to get you, as one is led to believe.