Submarine Warfare of To-day / How the Submarine Menace Was Met and Vanquished, with Descriptions of the Inventions and Devices Used, Fast Boats, Mystery Ships, Nets, Aircraft, &c. &c., Also Describing the Selection and Training of the Enormous Personnel Used in This New Branch of the Navy

by Charles W. Domville-Fife

Nearly all U-boats were fitted with a number of hydrophones and therefore were as well able to receive timely warning of an approaching surface ship as the surface ship was of the presence of the submarine. But the surface ship had the advantage of speed.

The result of all this was that when a German submarine heard a surface vessel approaching she dived to the bottom, if the water was not too deep or the sea-bed too rocky. Then shutting off her engines she listened. The surface ship, mystified by the sudden cessation of the noise she had been pursuing, also waited, and this stagnation sometimes lasted for hours. Then if the surface ship moved, as she was often compelled to do in order to avoid drifting with the tide away from the locality, the submarine moved also, and the one that stopped her engines first detected the other, but could not catch up to her again without deafening her own listening appliance. In which case the next move would probably be in favour of her opponent.

All of this is, perhaps, a little complicated, but a moment's pause for reflection will make this curious situation clear to the reader. And so the game went on, with decisive advantage to neither the surface ship nor the submarine. Darkness usually intervened and put an end to further man[oe]uvring, frequently allowing the submarine to escape.

A case of this kind occurred to a vessel, of a certain hydrophone flotilla, commanded by the author. For over four hours the U-boat eluded the pursuing surface ships by moving only when they moved and stopping when they too had stopped, darkness and a rising sea eventually favouring the escape of the submarine, which, a few hours later, was able to attack (unsuccessfully) a big surface ship less than thirty miles distant from the scene.

Nevertheless the hydrophone is a submarine instrument with a brilliant future. It has already been improved out of all resemblance to its original self, and more will undoubtedly follow. It is, however, purely an appliance for the detection of submarines when cruising beneath the surface, and not a weapon for their destruction. It should also be remembered that any improvement made in the efficiency of the hydrophone will benefit not only the surface ship, but also the submarine, for it cannot be supposed that under-water craft will be left without these wonderful submarine ears when their surface destroyers are equipped with them.

The alliance between the hydrophone and the depth charge is a natural one. The former instrument enables the surface ship to discover, first, the presence of a submarine in the vicinity, and, secondly, its approximate position. At this point its utility temporarily ceases and that of the depth charge begins. When a surface ship is hot on the track of a moving submarine she endeavours to attain a position directly over the top of her quarry, or even a little ahead, and then releases one or more depth charges according to whether the chance of a hit is good or only poor.

From this it will be apparent that whereas the hydrophone is the instrument used for the initial detection of the submarine, and afterwards for enabling the surface ship to get to close quarters with her submerged adversary, it is the depth charge with which the attack is actually made.

This weapon is really a powerful submarine bomb. It consists of several hundred pounds of very high explosive encased in a steel shell, with a special firing device which can quickly be set so that the charge explodes at almost any depth below the surface after being released from the above-water vessel.

The methods in use during the war for its release from the decks of surface ships were very diverse, the most usual being for a number of these weapons to be fitted on slides and held in place by wire slings which could be released by simply pulling out a greased pin or bolt.

When the depth charge rolled off the stern of the surface ship it sank to the "set depth" and then exploded like a submarine mine. The result was a shattering effect exerted through the water for several hundred feet around. If the submarine was close to the explosion her comparatively thin plates were nearly always stove-in. When she was over a hundred feet away, however, the rivets holding her plates together were often loosened, and the resulting leak frequently compelled her to come to the surface, where she could be destroyed by gun-fire.