Parliamentary debates in the late nineties indicated that British naval leaders entertained this same idea. In 1900, Viscount Goschen, who was then the First Lord of the Admiralty, dismissed the submarine as unworthy of consideration. "The idea of submarine navigation," he said, "is a morbid one. We need pay no attention to the submarine in naval warfare. The submarine is the arm of weaker powers." But Mr. Arnold-Forster, who was himself soon to become a member of the Admiralty, took exception to these remarks. "If the First Lord," he said, "had suggested that we should not build submarines because the problems which control them are not yet solved, I should have hesitated to combat his argument. But the First Lord has not said so: he has said that the Admiralty did not care to undertake any project for submarines because this type of boat could never be anything but the arm of the feeble. However, if this boat is made practical, the nation which possesses it will cease to be feeble and become in reality powerful. More than any other nation do we have reason to fear the submarine. It is, therefore, not wise to wait with indifference while other nations work at the solution of this problem without trying to solve it ourselves." "The question of the best way of meeting submarine attack," said Viscount Goschen at another time, "is receiving much consideration. It is in this direction that practical suggestions would be valuable. It seems certain that the reply to this weapon must be looked for in other directions than in building submarine boats ourselves, for it is clear that one submarine cannot fight another."
This prepossession dominated all professional naval minds in all countries, until the outbreak of the Great War. Yet the war had lasted only a few months when the idea was shown to be absurd. Practical hostilities soon demonstrated, as already said, that not only was the submarine able to fight another boat of the same type, but that it was the most effective anti-submarine agency which we possessed—so effective that the British Admiralty at once began the design of a special type of hunting submarine having a high under-water speed.
The fact is that the popular mind, in its attitude toward this new type of craft, is still too much under the spell of Jules Verne. There is still the disposition to look upon the submarine as an insidious vessel which spends practically all of its time under the water, stealthily slinks along, never once betraying its presence, creeps up at will to its enemy and discharges its torpedo. Yet the description which these pages have already given of its operations shows the falsity of this idea. It is important that we should keep constantly in mind the fact that the submarine is only occasionally a submarine; and that for the greater part of its career it is a surface boat. In the long journeys which the German U-boats made from the Heligoland Bight around Scotland and Ireland to those great hunting grounds which lay in the Atlantic trade routes, they travelled practically all the time on the surface of the water. The weary weeks during which they cruised around, looking for their victims, they also spent almost entirely on the surface. There were virtually only two circumstances which compelled them to disappear beneath the waves. The first of these was the occasion on which the submarine detected a merchant ship; in this case it submerged, for the success of its attempt to torpedo depended entirely upon its operating unseen. The second occasion which made it necessary to submerge was when it spied a destroyer or other dangerous patrolling craft; the submarine, as has been said, could not fight a vessel of this type with much chance of success. Thus the ability to submerge was merely a quality that was utilized only in those crises when the submarine either had to escape a vessel which was stronger than itself or planned to attack one which was weaker.
The time taken up by these disappearances amounted to only a fraction of the total period consumed in a cruise. Yet the fact that the submarine had to keep itself momentarily ready to make these disappearances is precisely the reason why it was obliged to spend the larger part of its time on the surface. The submarine has two sets of engines, one for surface travel and the other for subsurface travel. An oil-engine propels it on the top of the water, but this consumes a large amount of air, and, for this reason, it cannot be used when travelling under the surface. As soon as the vessel dives, therefore, it changes its motive power to an electric motor, which makes no inroads on the oxygen needed for sustaining the life of its crew. But the physical limitation of size prevents the submarine from carrying large storage batteries, which is only another way of saying that its cruising radius under the water is extremely small, not more than fifty or sixty miles. In order to recharge these batteries and gain motive power for subsurface travel, the submarine has to come to the surface. Yet the simple fact that the submarine can accomplish its destructive work only when submerged, and that it can avoid its enemy only by diving, makes it plain that it must always hold itself in readiness to submerge on a moment's notice and remain under water the longest possible time. That is, its storage batteries must always be kept at their highest efficiency; they must not be wasted by unnecessary travelling under the water; the submarine, in other words, must spend all its time on the surface, except those brief periods when it is attempting to attack a merchant ship or escape an enemy. Almost the greatest tragedy in the life of a submarine is to meet a surface enemy, such as a destroyer, when its electric batteries are exhausted. It cannot submerge, for it can stay submerged only when it is in motion, unless it is in water shallow enough to permit it to rest on the bottom. Even though it may have a little electricity, and succeed in getting under water, it cannot stay there long, for its electric power will soon be used up, and therefore it is soon faced with the alternative of coming to the surface and surrendering, or of being destroyed. The success of the submarine, indeed its very existence, depends upon the vessel spending the largest possible part of its time upon the surface, keeping its full supply of electric power constantly in reserve, so that it may be able to dive at a moment's notice and to remain under the water for the maximum period.
This purely mechanical limitation explains why the German submarine was not a submarine in the popularly accepted meaning of that term. Yet the fact that this vessel remained for the greater part of its existence on the surface was no particular disadvantage, so long as it was called upon to contend only with surface vessels. Even with the larger part of its decks exposed the U-boat was a comparatively small object on the vast expanse of the sea. I have already made clear the great disadvantage under which destroyers and other patrolling vessels laboured in their attempts to "hunt" this type of enemy. A destroyer, small as it is, was an immensely larger object than the under-water boat, and the consequence was that the lookout on a submarine, proceeding along on the surface, could detect the patrolling vessel long before it could be observed itself. All the submarine had to do, therefore, whenever the destroyer appeared on the horizon, was to seek safety under water, remain there until its pursuer had passed out of sight, and then rise again and resume its operations. Before the adoption of the convoy system, when the Allied navies were depending chiefly upon the patrol—that is, sending destroyers and other surface craft out upon the high seas to hunt for the enemy—the enemy submarines frequently operated in the same areas as the patrol vessels, and were only occasionally inconvenienced by having to keep under the water to conceal their presence. But let us imagine that the destroyer, in addition to its depth charges, its torpedoes, its guns, and its ability to ram, had still another quality. Suppose, for a moment, that, like the submarine, it could steam submerged, put up a periscope which would reveal everything within the radius of a wide horizon, and that, when it had picked up an enemy submarine, it could approach rapidly under the water, and discharge a torpedo. It is evident that such a manœuvre as this would have deprived the German of the only advantage which it possessed over all other war craft—its ability to make itself unseen.
No destroyer can accomplish any such magical feat as this: indeed, there is only one kind of vessel that can do so, and that is another submarine. This illustration immediately makes it clear why the Allied submarine itself was the most destructive enemy of the German submarine. When Robert Fulton, John P. Holland, and other authorities declared that the under-water vessel could not fight its own kind, it is evident that they had not themselves foreseen the ways in which their inventions were to be used. They regarded their craft as ships that would sail the larger part of the time under the waves, coming up only occasionally to get their bearings and to take in a fresh supply of air. It was plain to these pioneers that vessels which spent practically all their time submerged could not fight each other, for the sufficient reason that they could not see each other; a combat under these conditions would resemble a prize-fight between two blindfolded pugilists. Neither would such vessels fight upon the surface, for, even though they were supplied with guns—things which did not figure in the early designs of submarines—one boat could decline the combat simply by submerging. In the minds of Fulton and Holland an engagement between such craft would reduce itself to mutual attempts to ram each other under the water, and many fanciful pictures of the early days portrayed exciting deep-sea battles of this kind, in which submarines, looking like mighty sea monsters, provided with huge glaring headlights, made terrific lunges at each other. None of the inventors foresaw that, in such battles as would actually take place, the torpedo would be used, and that the submarine which was defeated would succumb to one of those same stealthy attacks which it was constantly meditating against surface craft.
Another point of the highest importance is that in a conflict of submarine against submarine the Allied boats had one great advantage over the German. Hans Rose and Valentiner and Moraht and other U-boat commanders, as already explained, had to spend most of their time on the surface in order to keep their batteries fully supplied with electricity, in readiness for the dives that would be necessary when the Allied destroyers approached. But the Allied submarine commander did not have to maintain this constant readiness; the reason, it is hardly necessary to say, is that the Allied submarine had no surface enemies, for there were no German surface craft operating on the high seas; the Grand Fleet at Scapa Flow was carefully attending to that very essential detail. Occasionally, indeed, our submarines were attacked by our own destroyers, but accidents of this kind, though uncomfortably frequent, were not numerous enough to interfere with the operation I have in mind. The statement seems almost like a contradiction in terms, yet it is entirely true, that, simply because the Allied submarines did not have to hold themselves constantly ready to submerge, they could in fact spend a considerable part of their time under the water, for they were not compelled to economize electric power so strictly. This gave them a great advantage in hunting the U-boats. British and American submarines could fully charge their batteries, drop under water and cruise around with enough speed to maintain a horizontal position at "periscope depth," that is, a depth just sufficient to enable them to project the periscope above the water whenever desired. This speed was so very slow—about one mile an hour—that it could be kept up an entire day without exhausting the electric batteries.
The net result was this: The German submarine necessarily sailed most of the time on the surface with its conning-tower and deck exposed, whereas the Allied submarine when on its hunting grounds, spent all of the daylight hours under water, with only the periscope visible from time to time for a few seconds. Just as the German U-boat could "spot" an Allied destroyer at a great distance without being itself seen, so could the periscope invariably see the German submarine on the surface long before this tiny object came within the view of a U-boat conning-tower. Our submarine commander could remain submerged, sweep the ocean with his periscope until he had picked up the German enemy; then, still under water, and almost invariably unseen, he could steal up to a position within range, and discharge a torpedo into its fragile side. The German submarine received that same treatment which it was itself administering to harmless merchantmen; it was torpedoed without warning; inasmuch, however, as it was itself a belligerent vessel, the proceeding violated no principle of international law.
II
The Allied submarines, like many other patrol craft, spent much of their time in those restricted waters which formed the entrances to the British Isles. Their favourite places were the English Channel, St. George's Channel, which forms the southern entrance to the Irish Sea, and the northern passage-way between Scotland and Ireland. At these points, it may be remembered, the cargo ships could usually be found sailing singly, either entirely unescorted, or escorted inadequately, while on their way to join a convoy or to their destinations after the dispersal of a convoy; these areas were thus almost the only places where the German submarines had much chance of attacking single vessels. The territory was divided into squares, each one of which was indicated by a letter: and the section assigned to each submarine was known as its "billet." Under ordinary circumstances, the Allied submarine spent all its time, while patrolling, on its own particular "billet"; only in case the pursuit of an enemy led it outside the "square" was it permissible to leave. Allied submarines also hunted the U-boats in the North Sea on the routes which the latter had to take in coming out or returning through the passages in the German mine-fields of the Heligoland Bight, or through the Skager Rack.