Surprise Attack.
In this case invisibility is the element of success. Admiral Sir Cyprian Bridge, G.C.B., in a letter to the Author once said: “When submerged the concealment of the submarine is practically perfect. If she has not been sighted up to the moment of diving, she will almost certainly reach, unobserved, the point at which she can make her attack.” And this opinion—shared for many years by all experts—has been amply proved in the present war.
A submarine must, however, blend with the surrounding sea in its ever-varying colours, lights and shades, in order that she may be as invisible as possible when cruising on the surface. The French Naval Authorities experimented off Toulon with a luminous paint of a sea-green colour; but this, although causing the hull to be almost totally invisible in certain weather, was found to be useless, as, on a bright day with a blue sky, the green showed up clear against the bluish tint of the surrounding sea. After many months of experimenting, a pale, sea-green, non-luminous paint was chosen as the best colour for French submarines. The British Admiralty also carried out a few experiments in this direction, and came to the conclusion that a dull grey was the most invisible shade. The German authorities decided in favour of a grey-brown.
When travelling submerged, with only the thin periscopic tube above the surface, it is almost impossible to detect the approach of a submarine before she gets within torpedo range; and when cruising on the surface she is equally as invisible at a distance of a few miles. These qualities enable the submarine in nearly all cases where her speed permits, to effect a surprise attack on a hostile battleship or cruiser when not closely screened by fast destroyers, whose duty it is to be ever on the watch for submarines.
As to the tactics which would be employed by a submarine (or flotilla) in attacking a hostile warship (or fleet), it is impossible to say, for, like the impromptu attacks of all “mosquito craft,” the exact method, or manœuvre, is arranged to suit the circumstances, and it is very seldom that two such attacks are carried out alike. Generally speaking, however, a hostile warship could be easily sighted, on a fairly clear day, from the flying-bridge of a submarine at a distance of 10 miles; but it would be practically impossible to detect the submarine from the deck of a warship at that distance. On sighting her object of attack the submarine would sink to the “awash” condition, and proceed for from 2 ½ to 5 miles, as might be deemed expedient. She would then submerge and steer by her periscopes, each of which has a field of vision of 60 degrees. He would be a very keen look-out who would be able to detect the few square inches of periscopic tube at a distance of three miles. As this distance lessened, it might be advisable, if the sea was very calm and if the object of attack was stationary, for the submarine to slacken speed, so as to prevent any spray being thrown off by the periscopic tube. Assuming, however, that the optical tube was seen by the enemy, it would be extremely difficult to hit it with gun-fire at a distance of one or two miles, or to damage the boat itself, which would probably be immersed to a depth of 12 or 15 feet. At a distance of about 2,000 yards, or just over one mile, the submarine would discharge her first torpedo, following it up with another at closer range from the second bow tube. A rapid dive would then probably be necessary in order to avoid the hail of shot which would plough up the waters around her. If the first two torpedoes missed their mark the submarine might either dive completely under the object of attack and then fire her stern tubes at close range, or else manœuvre below the surface for an attack from some other point.
One of the effects produced on fleets or individual warships in war time by the ever present possibility of submarine attack is, however, that they never remain at anchor or even stationary in an exposed position, and seldom—if wise—proceed without destroyers as advance and flank guards. These precautions double the difficulties of a successful submarine attack.
CHAPTER IX
ANTI-SUBMARINE TACTICS
In all warfare, new weapons of attack are, sooner or later, met by new methods of defence. The submarine and the aeroplane are at present the only weapons against which there is no true means of defence, and yet one is being used as an antidote for the other without, however, any very striking success so far. The seaplane may be able to distinguish the dark patch in the sea caused by the hull of the submarine in clear water, but she cannot destroy it, neither can she signal the exact locality to an accompanying destroyer flotilla, owing to the speed with which seaplane and submarine pass over and under each other; furthermore, in rough weather or in shallow muddy water no sign of the submarine when submerged is visible from above. The great value of the seaplane as an antidote for submarines lies, however, first in the fact that the water of the open sea is usually clear, and the submarine shadow is visible from above, and, secondly, in the great speed of these aircraft which enables them to quickly cover miles of sea in their search for hostile submarines and to report their presence in a given locality by wireless to all ships operating within range.
When the enormous superficial area of a zone of war, such as the North Sea and English Channel, is duly considered, however, the difficulty in quickly and reliably locating from the air the few scattered “submarine shadows” will be easily realized. To make this method of locating submarines even fairly reliable an enormous fleet of seaplanes would be required. Again seaplanes do not, in themselves, constitute a means of defence against submarine attack, they merely increase the likelihood of detection, but, in actual warfare, it has now been proved that for every submarine detected by seaplanes two others pass quite unobserved.
Many means of attack on submarines have been proposed; and no doubt some of these, in certain cases, would prove effective; but none can be relied upon. Therefore, one of the points in favour of the submarine still remains without its antidote. This is the moral effect; for if there is no absolutely reliable means of defence, there can be no feeling of security for surface warships or merchant vessels when anywhere within the danger zone of the submarine.
Let us now examine briefly what practical methods of defence a modern warship has against submarine attacks. Great speed is undoubtedly a surface ship’s most reliable defence; and when combined with a frequent change of course, would greatly reduce the chances of a successful under-water attack. Should hostile submarines be on the line of advance they would not know whether to wait and chance the enemy approaching within torpedo range or whether to run to starboard or port. This is, if the surface warship was steaming in an erratic course—not a zigzag course, for then it might be possible to estimate, within torpedo range, the position of the ship at a given point if the “tacks” were regular.
Should submarines be seen approaching, a surface vessel would do well to turn her stern to the attacking flotilla, presenting as small a target as possible, and deflecting the torpedoes by her propeller race.
The escape of the Battle Cruiser Queen Mary and the Light Cruiser Lowestoft, during the action in the Heligoland Bight, as described in the dispatch of Vice-Admiral Sir David Beatty, K.C.B., demonstrates what may be done by the skilful use of the helm on surface warships to frustrate submarine attacks. So interesting, and informative as to the actual fighting between British warships and hostile submarines, in this dispatch that I give it here in full. It should, however, be studied in conjunction with the comprehensive report—the first in the history of Naval warfare detailing submarine attack and reconnaissance—from Commodore Roger J. B. Keyes, C.B., of the British submarines, given on page 28.
“H.M.S. Lion,
1st September, 1914.
“Sir,—I have the honour to report that on Thursday, 27th August, at 5 a.m., I proceeded with the First Battle Cruiser Squadron and First Light Cruiser Squadron in company, to rendezvous with the Rear-Admiral, Invincible.
“At 4 a.m., 28th August, the movements of the Flotillas commenced as previously arranged, the Battle Cruiser Squadron and Light Cruiser Squadron supporting. The Rear-Admiral, Invincible, with New Zealand and four Destroyers having joined my flag, the Squadron passed through the pre-arranged rendezvous.
“At 8.10 a.m. I received a signal from the Commodore (T), informing me that the Flotilla was in action with the enemy. This was presumably in the vicinity of their pre-arranged rendezvous. From this time until 11 a.m. I remained about the vicinity ready to support as necessary, intercepting various signals, which contained no information on which I could act.
“At 11 a.m. the Squadron was attacked by three Submarines. The attack was frustrated by rapid manœuvring and the four Destroyers were ordered to attack them. Shortly after 11 a.m., various signals having been received indicating that the Commodore (T) and Commodore (S) were both in need of assistance, I ordered the Light Cruiser Squadron to support the Torpedo Flotillas.
“Later I received a signal from the Commodore (T), stating that he was being attacked by a large Cruiser, and a further signal informing me that he was being hard pressed and asking for assistance. The Captain (D), First Flotilla, also signalled that he was in need of help.
“From the foregoing the situation appeared to me critical. The Flotillas had advanced only ten miles since 8 a.m., and were only about twenty-five miles from two enemy bases on their flank and rear respectively. Commodore Goodenough had detached two of his Light Cruisers to assist some Destroyers earlier in the day, and these had not yet rejoined. (They rejoined at 2.30 p.m.). As the reports indicated the presence of many enemy ships—one a large Cruiser—I considered that his force might not be strong enough to deal with the situation sufficiently rapidly, so at 11.30 a.m. the Battle Cruisers turned to E.S.E., and worked up to full speed. It was evident that to be of any value the support must be overwhelming and carried out at the highest speed possible.
“I had not lost sight of the risk of Submarines, and possible sortie in force from the enemy’s base, especially in view of the mist to the South-East.
“Our high speed, however, made submarine attack difficult, and the smoothness of the sea made their detection comparatively easy. I considered that we were powerful enough to deal with any sortie except by a Battle Squadron, which was unlikely to come out in time, provided our stroke was sufficiently rapid.
“At 12.15 p.m. Fearless and First Flotilla were sighted retiring West. At the same time the Light Cruiser Squadron was observed to be engaging an enemy ship ahead. They appeared to have her beat.
“I then steered N.E. to sounds of firing ahead, and at 12.30 p.m. sighted Arethusa and Third Flotilla retiring to the Westward engaging a Cruiser of the Kolberg class on our Port Bow. I steered to cut her off from Heligoland, and at 12.37 p.m. opened fire. At 12.42 the enemy turned to N.E., and we chased at 27 knots.
“At 12.56 p.m. sighted and engaged a two-funnelled Cruiser ahead. Lion fired two salvoes at her, which took effect, and she disappeared into the mist, burning furiously and in a sinking condition. In view of the mist and that she was steering at high speed at right angles to Lion, who was herself steaming at 28 knots, the Lion’s firing was very creditable.
“Our Destroyers had reported the presence of floating mines to the Eastward and I considered it inadvisable to pursue her. It was also essential that the Squadrons should remain concentrated, and I accordingly ordered a withdrawal. The Battle Cruisers turned North and circled to port to complete the destruction of the vessel first engaged. She was sighted again at 1.25 p.m. steaming S.E. with colours still flying. Lion opened fire with two turrets, and at 1.35 p.m., after receiving two salvoes, she sank.
“The four attached Destroyers were sent to pick up survivors, but I deeply regret that they subsequently reported that they searched the area but found none.
“At 1.40 p.m. the Battle Cruisers turned to the Northward, and Queen Mary was again attacked by a Submarine. The attack was avoided by the use of the helm. Lowestoft was also unsuccessfully attacked. The Battle Cruisers covered the retirement until nightfall. By 6 p.m., the retirement having been well executed and all Destroyers accounted for, I altered course, spread the Light Cruisers, and swept northwards in accordance with the Commander-in-Chief’s orders. At 7.45 p.m. I detached Liverpool to Rosyth with German prisoners, seven officers and 79 men, survivors from Mainz. No further incident occurred.—I have the honour to be, Sir, your obedient Servant.
“(Signed) DAVID BEATTY,
“Vice-Admiral.
“The Secretary of the Admiralty.”
Quick-firing guns of the 3-inch and 6-inch type are certainly the best weapons for an attack on submarines. In combination with “sharp look-outs,” they could be used with effect from the elevated positions on the fore part of warships. The periscopic-tube of the submarine always proves a target for gun-fire; but a grey steel tube, 3 inches in diameter, at a distance of 1,000 yards requires “excellent” marksmanship to hit. That it can be done is proved by the sinking of the German submarine U.15 by the British Cruiser Birmingham in the North Sea. The effect of a shot carrying away the periscope is to blind the submarine, at least in one eye, she can then be run-down by the surface warship or destroyed by rapid gun-fire at close range.
Of course, if submarines were caught napping on the surface the guns of surface warships could quickly sink them; but another incident, similar to that which opened the naval engagements of the Russo-Japanese War, cannot be looked for in the naval engagements to come.
For a fleet engaged in bombarding or blockading, one of the best methods of defence would be to lower the torpedo nets, not close round each vessel, but suspended from “picket-boats” at a distance from the bombarding or blockading fleet. “Picketing” is also considered a good defence during daylight, but neither of these methods are reliable. A submarine might be able to dive unobserved under, or past, the destroyers acting as pickets, and it is this chance which causes these under-water craft to be a source of constant anxiety.
The torpedo-boat destroyer should prove a nasty enemy to the submarine. In warfare it is the duty of these 30-knot vessels to look after their under-water opponents.
It has been suggested that internal armour could be fitted to warships below the water-line, which would render the hulls able to withstand mine or torpedo explosions. At present this is practically impossible, as the great weight of this additional armour, combined with the ever-increasing size of guns and weight of above-water protection, would necessitate a vessel of such enormous displacement as to be quite impossible, if the important factor—high speed—has also to be maintained.
The defence of harbours against submarines is a problem which does not present nearly so many difficulties as the defence of moving ships. Portsmouth, for example, is closed by means of a submarine boom-defence, which is stretched across the mouth of the harbour. The entrance to the River Elbe (leading to the Kaiser Wilhelm Canal) is effectively closed to British submarines by boom-defences, mines, and submerged wire entanglements. Narrow waterways, such as the Straits of Dover, can be closed by the laying of contact-mines, and even broader seas can be made dangerous to submarines by the same method. An example of this is afforded by the laying of a British mine-field somewhere between the Goodwin Sands and the Dutch Coast, to prevent German submarines from penetrating into the English Channel.
There are so many reliable means of defending harbours and narrow waterways against submarines that it is unnecessary to say anything further here. But to protect moving ships at sea, under all conditions, certainly presents a most profound puzzle.
CHAPTER X
THE SUBMARINE TORPEDO
The submarine torpedo has become one of the principal naval arms. Not only does it supply the chief offensive power of the submarine, the torpedo-boat and the destroyer, but it is also carried as a separate arm, with a special highly-trained crew, by almost every warship afloat. At the beginning of hostilities the Naval Powers engaged owned considerably over 80,000 of these weapons, and one factory in England alone can make them at the rate of two a day. During the first few weeks of the Great War the torpedo was responsible for the sinking of warships to the value of over one million sterling. Had the German Fleet been on the high seas instead of in harbour and protected from torpedo raids by carefully-prepared submarine defences, there is little doubt but what several more of the enemy’s ships would have been sunk by this weapon. The fact that at first the British light cruisers suffered rather heavily—though in total loss of ships and men less than the German Navy—does not point to any advantage derived either from the type of torpedo used or from skill in this mode of warfare possessed by the Germans, but clearly to the timidity of the German main fleet, which was at the very beginning of hostilities withdrawn from the zone of war and placed behind fortifications, where it was safe from torpedo attack. The British Fleet, true to the policy of “attack and not defence,” began operations the moment war was declared, with results so brilliantly successful, and of such far-reaching and world-wide importance, that enumeration is well-nigh impossible. But while all these operations were in progress the British Fleet was more or less exposed to torpedo attack by any hostile submarines or fast surface craft which might succeed in getting past the cordon of protecting destroyers, while the German Fleet was safe, but ignominiously impotent. That the naval losses of Great Britain, with all her fleets at sea, have not been far greater than they have is in itself a victory of the greatest magnitude—a victory due entirely to consummate naval skill.
The modern torpedo varies in length from 14 to 19 feet, and weighs up to half a ton. It has an extreme range of 4,000 yards, or just over 2 ¼ miles. There are three types of torpedoes in use by the fleets at war. The British use the Whitehead Torpedo, the French the Whitehead and the Schneider, the Russians and the Japanese use the Whitehead; the Germans have a type of their own, known as the Schwartzkopf, and the Austrian arm is principally the Whitehead. All these types are alike in their essential features, and therefore need not be described separately.
The latest pattern 18-inch Whitehead torpedo is propelled by compressed air stored in that section of the weapon known as the air-chamber (see diagram). The air on being released is heated and expanded in a tiny three or four-cylinder engine which operates twin screws, moving “clockwise” and “anti-clockwise.” The “war-head” contains about 200 pounds of wet gun-cotton which is exploded on the torpedo striking an object. The essential features of the Whitehead torpedo are shown in the diagram.[[9]]
This torpedo maintains a speed of 42 knots for 1,000 yards, 38 knots for 2,000 yards, 32 knots for 3,000 yards, and 28 knots for 4,000 yards. Thus, if discharged at a distance of half a mile it reaches its object in about 45 seconds.
Sketch showing the essential parts of a Whitehead torpedo. A. Pistol, detonator, primer, which causes the explosion of “B” when the torpedo strikes an object. B. Explosive head, filled with wet gun-cotton. (The “war-head” is substituted by a weighty dummy during practice.) C. Air chamber with compressed air, at a pressure of approximately 1350 lbs. per square inch, for action. The chamber is tested to stand a pressure of 1700 lbs. per square inch. D. Balance chamber, containing mechanism for regulating the depth of submergence at which the torpedo is adjusted to run. E. Engine-room, containing propelling machinery (I.H.P. 60 in latest 18-in. type). F. Buoyancy chamber—a practically empty chamber—to give the necessary buoyancy to the torpedo. G. Gyroscope. An instrument for correcting any deviation of the torpedo from the line of fire. H. Rudders, and mechanism for operating. I. Twin-screws, operating “clockwise” and “anti-clockwise.”
Torpedoes are fired—or ejected—into the sea from surface or submerged tubes, and on striking the water are propelled by their own engines in an absolutely straight course towards the target. The exact mechanism of the submerged tube—which is used in surface warships as well as in submarines—is a naval secret. When fired from a surface tube the torpedo sinks immediately to a depth of about 10 to 14 feet, and maintains this depth until it strikes its object. When fired from a submerged tube it rises—if necessary—to the same level. A torpedo always proceeds towards its object of attack at a depth of a few feet below the surface. This, combined with speed, renders it almost impossible to destroy an approaching torpedo by gun-fire. So marvellous is the mechanism of these little weapons that in anything like favourable circumstances they may be depended upon, if well aimed, to strike within a yard or two of the spot aimed at. This accuracy is due almost entirely to the gyroscope, which, briefly described, is a rotating wheel automatically controlling the torpedo’s course.
Although for many years torpedoes have been carried by nearly all types of service warships, none of them were really ideal for this kind of warfare. A new field for the torpedo was, however, opened out by the introduction of the submarine boat. In order to be effective the torpedo must be discharged from a distance under 4,000 yards—preferably from a point less than half this distance from the object of attack. This means that the vessel carrying the torpedo would have to get within a mile, or at least a mile and a-half, of her object of attack before discharging a torpedo. For a surface vessel to accomplish this in the face of a heavy cannonade from quick-firing guns would be extremely risky. To make a quick rush to close quarters, if possible, by several vessels from different points, was the only chance of delivering a successful torpedo attack on a hostile warship; unless, of course, she was favoured by fog or darkness at the right moment—favourable conditions which would seldom obtain in actual warfare. Again, every increase in the speed of the big surface warship rendered the task of the ordinary torpedo-boat and destroyer more difficult because in the event of a threatened attack the larger vessel would make use of her speed to keep out of torpedo range while her powerful guns were repelling the attacking torpedo-boat.
The hour of the torpedo came with the perfection of the submarine. All the conditions of an ideal torpedo-boat were fulfilled—invisibility rendering daylight attacks possible; almost perfect immunity from gun-fire enabling the torpedo to be discharged at closer range; submerged discharge removing the likelihood of the weapon being exploded by accurate gun-fire before being discharged; speed on the surface enabling the “carrying” vessel to manœuvre for position; moderate speed when submerged enabling an attack under all reasonably tactical conditions; and comparatively large displacement giving good cruising qualities, wide range of action, and enabling a large number of torpedoes and tubes being carried.
CHAPTER XI
SUBMARINE MINES
If the Russo-Japanese war was the first to fully demonstrate the value of the explosive mine, the Great European Conflict has certainly brought this weapon to the forefront in the rapidly growing science of submarine warfare. During the first few weeks of the naval fighting several warships, beginning with H.M.S. Amphion, and many merchant vessels representing millions of pounds sterling, were destroyed by these weapons. Had it not been for the foresight of the British Admiralty in providing a very large fleet of mine-sweepers, aided by seaplanes, there can be no doubt but what the shipping of all countries—neutrals and belligerents alike—would have suffered far greater losses.
LAUNCHING A GERMAN TROTYL MINE.
A GERMAN SUBMARINE TROTYL MINE ON THE DECK OF A MINE-LAYER.
These mines contain the famous T.N.T., or Trotyl explosive.
The indiscriminate scattering of mines across the trade routes, as carried on by Germany immediately on the outbreak of war, and before hardly any of the ships at sea belonging to neutral countries could be warned to avoid the zone of operations, has never before been so ruthlessly resorted to by a big civilised power.
The system of defence consists of the mooring of these mines in such positions as to make it almost impossible for hostile ships to pass without either striking or coming within the destructive zone of one or more of them. What are known as floating mines are those set adrift to be washed about by the tide. They explode immediately on being struck by a passing vessel, and, of course, do not discriminate between friend and foe. The systems of destroying hostile mine-fields consist of counter-mining, or placing other mines in the enemy’s field and destroying it by their explosion, and by sweeping. The latter method is the one mostly employed in modern warfare. The boats taking part in the sweep place themselves one on each side of the mine-field, and between them hangs a long wire rope, weighted in the centre to keep it well submerged. They then move forward, sweeping the mines to the surface or exploding them harmlessly. It is, however, very dangerous but highly necessary work.
There are two kinds of submarine mines, one is designed to explode on being struck by a passing vessel, and is called a contact mine, and the other is fired from the shore by an electric current, and is known as an observation mine. The explosive principally used is wet gun-cotton or Trotyl, owing not only to the safety with which they can be stored and manipulated, but also to the fact that they seldom explode in sympathy with neighbouring mines, requiring to be actually fired. The importance of this will be more fully realised when it is remembered that in warfare it is often necessary to explode certain mines over which hostile ships are endeavouring to pass, while leaving others in fairly close proximity intact, ready to repel a second invasion or to destroy ships nearer to them. The actual explosion is caused by an electric current, either from the shore or from a battery in the mine itself, causing the detonation of fulminate of mercury in conjunction with a small priming charge of dry gun-cotton. Mines are often laid in a series, connected to a battery on the sea-bed in the centre of the line of defence.
The observation mine is mostly used for defending the approaches to harbours, as an observer on shore can watch the movements of hostile warships and explode each mine when the vessel passes over it. Contact mines, on the other hand, are used wherever an enemy’s fleet is likely to pass. They are anchored to the sea-bed by means of a cable and heavy weight, and are allowed to float a few feet below the surface. They explode immediately on contact. At times an unscrupulous or demoralised enemy will simply throw a number of these mines overboard and allow them to float at the mercy of wind and tide. They then become a terrible danger to the shipping of all nations, as once they are left unwatched it is extremely difficult to tell with any degree of certainty where they will eventually proclaim their presence by devastating explosions. Happily for the whole seafaring world, this method is seldom resorted to, as mines set adrift in this way become a danger to both friend and foe. In the Russo-Japanese war several ships were destroyed by their own mines.
There are many different kinds of submarine mines, both of the observation and the contact type. Some are spherical in shape and others cylindrical. Some are moored close down to the sea-bed with a very heavy explosive charge (200–500 lbs. of gun-cotton), and have a small buoyant globe floating above them, which, when struck, fires the mine below. Others, known as secret-mines, are kept continually moored in the waterways leading to important naval harbours, and are only allowed to rise sufficiently high from the sea-bed to be struck by passing vessels in times of emergency. The type most generally used is, however, the ordinary offensive contact mine, which contains a powerful explosive charge and is anchored in the path of hostile warships. These mines are usually automatically sown in large numbers over a wide area of sea by the mine-laying fleets.
CHAPTER XII
MINE-LAYING FLEETS
The regular mine-laying fleets of the powers at war are composed of the following vessels, all of which are fitted with special apparatus for the work. Submarine mines can, however, be laid by any vessel, and it is therefore almost impossible to say exactly what ships are engaged in this work. Both Germany and Austria have converted a large number of their merchantmen into mine-layers. England, in reply, has converted a large number of small steamers into mine-sweepers. Russia is a strong believer in explosive mines, and has strewn the gulfs of Finland and Riga with them. Japan, being on the offensive, is employing more mine-sweepers than layers. France has an elaborate system of submarine mine defence for all her important harbours, and maintains a small fleet at each base, known as the “defence mobile.” These vessels are all capable of both mine-laying and sweeping.
The submarine mine is primarily the defence of the weaker naval power, and therefore a fleet acting on the defensive, either temporarily or permanently, requires more mine-layers than mine-sweepers, but the reverse is naturally the case with a fleet acting on the offensive. Although this may be taken as a general rule, it does not imply that a strong naval power like Great Britain, whose policy is attack and not defence, needs no mines or mine-layers. On the contrary, the laying of counter mines is one of the ways of destroying an enemy’s mine-field; and even the strongest fleet cannot guard every portion of a long coast line with many harbours exposed to attack. The judicious laying of mine-fields will often prevent raids by hostile submarines and torpedo-boats; and will limit the theatre of operations, as was done by the British Navy in the southern portion of the North Sea in October, 1914. The axiom that a really strong navy needs to be strong in every branch, therefore holds good in this, as in all other respects.