While it has been shown that the submersible of to-day, as a fighting machine, is considerably limited, and in no sense endangers the existence of the capital ship, nevertheless in the new huge submersible it seems that the ideal commerce-destroyer has been found. This vessel possesses the necessary cruising radius to operate over sufficient distances to control important routes; it makes a surface speed great enough to run down cargo steamers, and has a superstructure to mount guns of considerable power (up to six-inch). It embodies almost all the qualifications of the light surface cruiser, with the additional tremendous advantage of being able to hide by submergence. To be completely successful, it must operate in flotillas of hundreds in waters that are opaque to aërial observation. Germany has but a limited number of these submersibles, otherwise she would be able to crush the Allied commerce.
The ideal submersible commerce-raider should be a vessel of such displacement that she could carry a sufficient number of large guns in her superstructure to enable her to fight off the attack of surface destroyers and the smaller patrol craft.[2] She should be capable of cruising over a large radius at high speed, both on the surface and submerged. The supersubmersible flotillas should comprise fifty or sixty of these units. The attack on the trade routes should be made by a number of flotillas operating at different points at unexpected times. To-day Germany has concentrated her submarine war particularly in the constricted waters about England. It is here that the shipping is most congested, and therefore the harvest is richest, but it is also easier to protect the trade routes over these limited areas of water by patrols, nets, etc., than it would be to protect the entire trans-oceanic length of the steamship lanes. If the submersible were capable of dealing directly with the destroyer in gun-fighting, a tremendous revolution would take place in the tactics of "submarine swatting." Then it would be difficult to see how the submersible could be dealt with.
Improvement in motive machinery is the vital necessity in the development of the submersible. The next few years may see unexpected strides taken in this direction. A great deal will also be accomplished in perfecting methods of receiving sounds under water, particularly in relation to ascertaining the direction of these sounds. When this is done, it will be possible for the submersible commander to tell a great deal about the positions of the vessels above him, and thus his artificial ears will compensate to a great extent for his blindness. By the addition of a greater number of torpedo-tubes, and the improvement of their centralized control in the hand of the commander at the periscope, along lines which we are now developing, it will be possible for the submersible to achieve a greater effectiveness in its torpedo fire. Probably torpedoes will then be used only against the more important enemy units, such as battleships, cruisers, and the like. To be certain of striking these valuable targets would be worth expending a number of torpedoes in salvo fire.