Submarine Warfare of To-Day

by Charles William Domville-Fife

  The second attack on the Scandinavian convoy occurred on 12th December. The escort consisted of two destroyers, the Partridge and Pellew, with four armed trawlers. Fortunately the convoy was comparatively a small one, for it was attacked and almost totally destroyed in the North Sea by four of the largest German destroyers. H.M.S. Pellew, although badly damaged, succeeded in returning to England.

  It may be rightly thought that in both these cases the escorting flotilla was not strong enough, but it should be remembered that if heavier ships had been employed they would have been much less able to cope with a submarine attack. The escort in both cases was purely an anti-submarine defence, and only on the Scandinavian and Netherlands routes was a surface attack at all possible, because all exits from the North Sea were securely closed by the strategic positions occupied by the Grand Fleet and the battle cruiser squadrons, in conjunction with subsidiary fleets at Harwich and extensive mine-fields.

  When it became apparent that surface as well as submarine attacks on the North Sea convoys had to be provided against, other means were promptly adopted, and no further disasters occurred.

  The strong escort accompanying the transports bringing to Europe the first American army were attacked at night by a submarine, but succeeded in avoiding the torpedoes fired. This was due to the smartness with which the United States warships were manœuvred. Three subsequent attacks on the same convoy route also failed.

  The Report of the War Cabinet for the year 1917 gives some remarkable figures in support of the convoy system. On the Atlantic routes about 90 per cent. of the ships were formed into fleets and escorted. From the inauguration of this system the loss on these routes from all causes was 0.82 per cent., and if all the trade routes to and from the United Kingdom are included, the loss was only 0.58 per cent. With these figures in mind, who will deny that the navy is the surest form of national as well as Imperial insurance?

  CHAPTER X

  The Mysteries of Submarine Hunting Explained

  When all is said and done, anti-submarine warfare is very like big-game hunting. Success depends entirely on the initiative, skill and resource of the individual hunter. Contrary to general belief, there is, at present, no sovereign remedy for the depredations of under-water craft with their torpedoes and mines. There are, however, several recognised methods of attack and defence employed by surface ships in this newest form of naval warfare.

  When the new navy took the seas in 1914-1915, bases were established not only round the coasts of the British Isles, but also in the more distant seas. The principal danger zones were, however, the North Sea, the English Channel, the Irish Sea, the Mediterranean and the eastern portion of the North Atlantic. It was through these waters that every hostile submarine must pass on its voyage out and home.

  This geographical factor restricted the theatre of major operations to some 180,000 square miles of sea. Minor offensive measures might have to be adopted against individual U-boats cruising at long distances from their bases, as actually occurred off the United States coast, but the fact of Germany possessing large submarine bases only along her own North Sea coast, and temporary ones on the Flanders littoral, enabled a concentration of Allied anti-submarine craft to be made in the narrow seas which afforded the only means of entry and exit to and from those bases.

  The same may be said of Austria in the Adriatic and of Turkey behind the Dardanelles.

  This favourable combination of circumstances would not occur if (however unthinkable) England, France or the United States were ever to wage a rigorous war against shipping. The large number of oversea naval bases possessed by these Powers would cause every sea to become a danger zone within a few hours of the commencement of hostilities. No effective concentration of hostile surface craft would be possible with the zone of operations spread over the water surface of the entire globe, and if the bases themselves were secured by predominant battle fleets, or numbers of heavily armed monitors, the seas would quickly become impossible for purposes of hostile transport.

  This geographical restriction of the German and Austrian danger zones made effective concentration of the Allied anti-submarine fleets and their devices possible. The 180,000 square miles of sea, forming the theatre of major operations, was, on special charts, divided into areas, comprising a few hundred square miles of sea. Each area was given a distinctive number, and a base was established for its own patrol and minesweeping fleet.

  The areas themselves were again subdivided on special charts into squares or sections. Each square covered a few leagues of sea and was known by an alphabetical sign. In this way the waters of the submarine danger zone were divided into areas, with their bases and protective fleets, and squares with their respective squadrons or ships.

  Fig. 20.—Diagram showing division of sea into anti-submarine patrol areas.

  Each square of sea was covered once or twice daily by its own patrol ship or flotilla. Where the danger was less the patrol was not so frequent and the squares were almost indefinite in size, but where the chances of successful operations were exceptional, as in the Straits of Dover, additional offensive measures were employed (see under Mine Barrages).

  This, then, was the chess-board on which the game of submarine warfare was played. To facilitate communication between the different patrols spread over the squares of sea, wireless was fitted in many ships, and war signal stations were erected on prominent points of land. Each base was able to communicate by wireless with any of its ships out on patrol duty, and was also connected by land-line telegraph, telephone and wireless with naval centres.

  These latter were head intelligence offices, usually situated at the great bases of the battle fleets. In this way any concentration of hostile surface warships noticed by the patrols (sometimes submarines were employed, especially in the Heligoland Bight) could be communicated in a few minutes to the admirals commanding the Grand Fleet, the Battle Cruiser Squadron or other large fighting organisations.

  At the naval centres the movements of hostile submarines were recorded on charts. If, for example, it was reported from a patrol boat that the U16 had torpedoed a ship in square “C,” area 41, at 10 a.m. (G.M.T.6) on 4th August, and the patrol had arrived on the scene too late to be of any service, a warning could be wirelessed to hundreds of vessels on the seas surrounding the scene of outrage to keep a careful look-out for the U16.

  Fig. 21.—Diagram showing how an area is covered by patrols. A. Unit or flotilla of ships may proceed out from the base on course indicated by arrows B, which would be called the “Northern Inner Beat,” and return to harbour on course A, “Northern Outer Beat.” Other units of ships would simultaneously follow the course E. These and adjacent squares of sea would be covered daily by one or more ships of each unit. The southern half of the area would be patrolled in the same way. The “Outer Beat” is shown by the arrows C, and the “Inner Beat” by the arrows D. The points +F show the possible positions of armed patrols acting independently of any unit or flotilla.

  Subsequently a further message might come to the naval centre that the same submarine had been chasing a merchantman in square “D,” “E” or “F” in the adjoining area. A concentration of fast ships, such as destroyers, M.L.’s or coastal motor boats, could then be made so as to intercept the raider or enclose her in a circle while other vessels hunted her down.

  In a like manner important convoys coming down the coast, or entering a danger zone from the open sea, could be met by a local flotilla and escorted to a rendezvous with a flotilla from the adjoining area. In this way they were passed through the submarine and mine infested seas to and from their harbour terminus.

  Almost the same methods were employed in dealing with the thousands of German mines. But to describe that part of anti-submarine warfare here would be to encroach on the subject of a succeeding chapter.

  Patrols

  The method of patrolling the areas and squares of sea was comparatively simple, though the same cannot be said of the actual work. The line
s of patrol were called “beats,” and there was usually an “inner” and an “outer” beat for each unit or flotilla of ships. If when a ship (or a unit) reached her allotted square, from which the line of patrol extended, she elected to proceed on the inner beat, she would generally accomplish the return journey to the point of departure on the outer beat, thus covering her respective zone of patrol, but leaving the exact route to the discretion of the commanding officer. In this way no hostile submarine with a knowledge of the system could be sure of when or where a patrol ship would be met. In the same way it was left to the commander of a flotilla to either divide his ships into pairs, single units, or to maintain them as a homogeneous fleet, so that any combination of hostile submarines could not be made which would be sure of being able to attack a single patrol. Such an enemy combination might encounter a single ship, but it might also walk into the arms of a whole flotilla; or it might attack a single ship only to find itself surrounded by a following fleet.

  Fig. 22.—Diagram illustrating the operations of a hydrophone flotilla composed of armed motor launches. Each vessel is given a number, and the flotilla proceeds in line-abreast along the course shown by the dotted lines. Each vessel is one mile from the other, and the whole line stops by signal at the point marked with a cross. Hydrophones are put in operation, and after a period of listening the flotilla continues on its course, as no submarine sounds are heard. The flotilla turns to head south, and a stop is again made to listen on the hydrophones. This time the sound of a hostile submarine is heard by vessel No. 1, bearing S.W. This report is confirmed by vessel No. 2 hearing the same sound, bearing a few degrees farther W. The two bearings A and B are then drawn on a chart, and the point where the two lines cross is the approximate position of the invisible submarine. The attack with depth charges is then ordered.

  The beats which were most distant from the base were given to the largest ships. This was done because it was often impossible for the more distant patrols to reach a place of shelter before one of the fierce gales which swept the northern seas was upon them. Trawlers, large steam yachts and converted merchantmen were usually employed on squares more than one hundred miles distant from a harbour of refuge, while motor launches kept watch and ward on the seas closer inshore.

  The duration of patrols varied according to their position. Some lasted three weeks and others only a few days or hours. When the ships returned to their base after a spell at sea they were given a corresponding “rest” in harbour. A three weeks’ patrol meant several days’ “stand-off,” while a two or three days’ patrol entitled the ship to twenty-four hours in the comparative comfort of a harbour.

  It must not be imagined, however, that a stand-off meant entire idleness or thorough rest. There were duties to perform which robbed it of much that it was intended to give. Ships had to be coaled, provisioned, painted or repaired. Engines had to be overhauled, sentries posted ashore, a guard to be furnished, and every day one ship in each unit that was in harbour had to be manned and in readiness for emergencies.

  Hydrophone Flotillas

  We now come to the actual methods employed by surface craft when attacking submarines. Although, as previously stated, much was left to individual initiative, there were, nevertheless, certain recognised methods.

  Taking as an example the operations of a hydrophone flotilla of armed motor launches, the number of vessels forming the unit was usually five. When out scouting for the enemy they proceeded in line-abreast for about one sea mile, then stopped their engines and listened on their hydrophones for the noise of a submarine cruising in the vicinity. If nothing was heard the mile-long line of miniature warships advanced another mile and again stopped to listen. This manœuvre was repeated until one or other of the ships heard the familiar sound of a U-boat. Nothing might be visible on the surface of the sea, but if this was the case and the noise came up from the ocean depths over the electrified wires of the detector, it was conclusive proof that a submarine was in the near vicinity.

  The M.L. first detecting the noise hoisted a signal (flag by day and coloured electric light by night), giving the direction from which the sound came (see Fig. 22). The next ship in the line to receive the sound on its instruments then hoisted a signal, also giving the bearing—i.e. N.N.W., E.S.E., etc. If the two coincided in regard to direction, the attack commenced. If, however, they did not agree in this important respect, the line of patrol ships advanced another mile and listened again.

  The flag-ship of the unit on receiving the direction from one or more ships marked the lines of sound on a chart (as in Fig. 22), and when this was substantiated by another ship the point where the two lines crossed was known to be the position of the hostile submarine, and the attack was ordered.

  As to the exact method of an anti-submarine attack little need be said here beyond the fact that the ships advanced at full speed, manœuvring into a special formation which enabled them to cover about half a square mile of sea with the explosive force of their collective depth charges.

  When the attack had been completed all vessels engaged resumed their stations and waited with quick-firing guns ready in case the monster should rise from the deep to make a dying effort to destroy her pursuers.

  The tactical methods of anti-submarine attack were, of course, numerous, and they varied according to the speed of the surface ships engaged. What was possible of accomplishment by fast-moving coastal motor boats or the larger-sized M.L.’s proved impracticable for the more heavily armed but slow-moving trawlers and drifters. The tactics of these latter craft were often of the simplest character, and consisted principally of either independent attacks with the aid of hydrophones and depth charges, or, more frequently, the assumption of an innocent air in order to induce the submarine to open the attack at close range.

  Thornycroft & Co., Ltd.

  The Result of a Direct Hit

  A photograph left by the Germans in Ostend showing a coastal motor boat washed ashore after the great raid.

  In many respects this proved the most effective method of anti-submarine warfare. Not only did it frequently cause the under-water craft to rise to the surface and commence the attack by gun-fire, in order not to expend a valuable torpedo on what appeared to be an unarmed and helpless ship, but it also produced a moral effect throughout the German submarine flotillas.

  When a few U-boats had been either sunk or damaged in this way the news that every Allied ship was heavily armed circulated among the enemy personnel, and they became very nervous of attacking in any position except totally submerged. This meant the loss of at least one torpedo, out of from five to ten carried, for every attack made, whether successful or unsuccessful, and the latter were predominant.

  It soon became apparent that either they must risk surface attacks and so save their torpedoes, or else curtail their cruises to meet the rapid expenditure of their only submarine weapon. This does not, of course, cover the activities of under-water mine-layers, whose nefarious purpose consisted simply of laying their mines wherever they appeared most likely to catch Allied shipping. These craft were usually armed with torpedoes as well as mines, to enable them to continue the work of destruction when the cargo of the latter had been safely laid. In this way the problem of combating the German submarine offensive resolved itself into two parts, one being to checkmate the commerce raider and the other the mine-layer. With the second of these difficulties we shall deal in a later chapter.

  Many merchantmen, both Allied and neutral, owed their escape to this camouflage warfare, which was brought to a high pitch of perfection and daring in the now famous mystery ships.

  What may be said to form the second method of anti-submarine warfare was the decoy or camouflage system. Of primary importance in this category were the mystery ships already described, but there were also innumerable other ruses de guerre which increased its efficiency.

  To describe one of these will enable the reader to draw on his own imagination for the remainder. A vessel was steaming in from the
Atlantic and was about a hundred miles from the Cornish coast when she was attacked by a submarine above water. The surface ship was heavily armed, but instead of using her weapons at once she sent out frantic wireless signals for assistance. Every few minutes the call went far and wide in plain Morse.

  The shells from the submarine splashed into the sea around, but none struck the target for some minutes. Had the surface ship desired, she could in all probability have avoided the under-water craft by using her superior speed, but instead she dropped back, allowing the submarine to catch up to her, and the shells began to burst unpleasantly close.

  Still the frantic wireless calls went forth. First the simple message: “I am being attacked by a large German submarine.” Then the vehemence increased to: “I am being heavily shelled.” A few minutes elapsed and then the call: “Help. Submarine gaining on me.” And finally: “Abandoning ship.”

  At this point the submarine was close astern and the liner slowing down preparatory to lowering her life-boats. The shells were damaging her superstructure, but a heavy swell interfered with the German marksmanship. Then came the surprise. A life-boat on the liner’s poop was hoisted clear of the deck and from under its cover there appeared the lean grey muzzle of a 4.7-inch gun. A few sharp blasts of cordite and the submarine sagged and disappeared.