Yet there was no mystery about the immunity which these great fighting vessels were enjoying; the submarine problem, so far as it affected the battle fleet, had already been solved. The explanation was found in the simple circumstance that, whenever the dreadnoughts went to sea, they were preceded by a screen of cruisers and destroyers. It almost seemed as though these surface craft were serving as a kind of impenetrable wall against which the German U-boats were beating themselves in vain. Yet to the casual observer there seemed to be no reason why the submarines should stand in any particular terror of the destroyers. Externally they looked like the least impressive war vessels afloat. When they sailed ahead of the battle squadrons, the destroyers were ungraceful objects upon the surface of the water; the impression which they conveyed was that of fragility rather than of strength, and the idea that they could ever be the guardians of the mighty battleships which sailed behind them at first seemed almost grotesque. Yet these little vessels really possessed the power of overcoming the submarine. The war had not progressed far when it became apparent that the U-boat could not operate anywhere near this speedy little surface vessel without running serious risk of destruction.
Until the reports of submarine fighting began to find their way into the papers, however, the destroyer was probably the one type of warship in which the public had the smallest interest. It had become, indeed, a kind of ugly duckling of the Navy. Our Congress had regularly neglected it; year after year our naval experts had recommended that four destroyers be built for every battleship, and annually Congress had appropriated for only one or two. The war had also found Great Britain without a sufficient number of destroyers for the purpose of anti-submarine warfare. The Admiralty had provided enough for screening the Grand Fleet in cruising and in battle, but it had been called upon to divert so many for the protection of troop transportation, supply ships, and commerce generally that the efficiency of the fleet had been greatly undermined. Thus Britain found herself without enough destroyers to meet the submarine campaign; this situation was not due to any lack of foresight, but to a failure to foresee that any civilized nation could ever employ the torpedo in unrestricted warfare against merchant ships and their crews.
The one time that this type of vessel had come prominently into notice was in 1904, when several of them attacked the Russian fleet at Port Arthur, damaging several powerful vessels and practically ending Russian sea power in the Far East. The history of the destroyer, however, goes back much further than 1904. It was created to fulfil a duty not unlike that which it has played so gloriously in the World War. In the late seventies and early eighties a new type of war vessel, the torpedo boat, caused almost as much perturbation as the submarine has caused in recent years. This speedy little fighter was invented to serve as a medium for the discharge of a newly perfected engine of naval warfare, the automobile torpedo. It was its function to creep up to a battleship, preferably under cover of darkness or in thick weather, and let loose this weapon against her unsuspecting hulk. The appearance of the torpedo boat led to the same prediction as that which has been more recently inspired by the submarine; in the eyes of many it simply meant the end of the great surface battleship. But naval architects, looking about for the "answer" to this dangerous craft, designed another type of warship and appropriately called it the "torpedo boat destroyer." This vessel was not only larger and speedier than its appointed antagonist, but it possessed a radius of action and a seaworthiness which enabled it to accompany the battle fleet. Its draft was so light that a torpedo could pass harmlessly under the keel, and it carried an armament which had sufficient power to end the career of any torpedo boat that came its way. Few types have ever justified their name so successfully as the torpedo boat destroyer. So completely did it eliminate that little vessel as a danger to the fighting ships that practically all navies long since ceased to build torpedo boats. Yet the destroyer promptly succeeded to the chief function of the discarded vessel, that of attacking capital ships with torpedoes; and, in addition to this, it assumed the duty of protecting battleships from similar attack by enemy vessels of the same type.
It surprises many people to learn that the destroyer is not a little boat but a warship of considerable size. This vessel to-day impresses most people as small only because all ships, those which are used for commerce and those which are used for war, have increased so greatly in displacement. The latest specimens of the destroyer carry four-or five-inch guns and twelve torpedo tubes, each of which launches a torpedo that weighs more than a ton, and runs as straight as an arrow for more than six miles. The Santa Maria, the largest vessel of the squadron with which Columbus made his first voyage to America, had a displacement of about five hundred tons, and thus was about half as large as a destroyer; and even at the beginning of the clipper ship era few vessels were much larger.
Previous to 1914 it was generally believed that torpedo attacks would play a large part in any great naval engagement, and this was the reason why all naval advisers insisted that a large number of these vessels should be constructed as essential units of the fleet. Yet the war had not made much progress when it became apparent that this versatile craft had another great part to play, and that it would once more justify its name in really heroic fashion. Just as it had proved its worth in driving the surface torpedo boat from the seas, so now it developed into a very dangerous foe to the torpedo boat that sailed beneath the waves. Events soon demonstrated that, in all open engagements between submarine and destroyer, the submarine stood very little chance. The reason for this was simply that the submarine had no weapon with which it could successfully resist the attack of the destroyer, whereas the destroyer had several with which it could attack the submarine. The submarine had three or four torpedo tubes, and only one or two guns, and with neither could it afford to risk attacking the more powerfully armed destroyer. The U-boat was of such a fragile nature that it could never afford to engage in a combat in which it stood much chance of getting hit. A destroyer could stand a comparatively severe pounding and still remain fairly intact, but a single shell, striking a submarine, was a very serious matter; even though the vessel did not sink as a result, it was almost inevitable that certain parts of its machinery would be so injured that it would have difficulty in getting into port. It therefore became necessary for the submarine always to play safe, to fight only under conditions in which it had the enemy at such a disadvantage that it ran little risk itself; and this was the reason why it preferred to attack merchant and passenger ships rather than vessels, such as the destroyer, that could energetically defend themselves.
The comparatively light draft of the destroyer, which is about nine or ten feet, pretty effectually protects it from the submarine's torpedo, for this torpedo, to function with its greatest efficiency, must take a course about fifteen feet under water; if it runs nearer the surface than this, it comes under the influence of the waves, and does not make a straight course. More important still, the speed of the destroyer, the ease with which it turns, circles, and zigzags, makes it all but impossible for a torpedo to be aimed with much chance of hitting her. Moreover, the discharge of this missile is a far more complicated undertaking than is generally supposed. The submarine commander cannot take position anywhere and discharge his weapon more or less wildly, running his chances of hitting; he must get his boat in place, calculate range, course, and speed, and take careful aim. Clearly it is difficult for him to do this successfully if his intended victim is scurrying along at the rate of thirty or forty miles an hour. Moreover, the destroyer is constantly changing its course, making great circles and indulging in other disconcerting movements. So well did the Germans understand the difficulty of torpedoing a destroyer that they practically never attempted so unprofitable and so hazardous an enterprise.
Torpedoes are complicated and expensive mechanisms; each one costs about $8,000 and the average U-boat carried only from eight to twelve; it was therefore necessary to husband these precious weapons, to use them only when the chances most favoured success; the U-boat commander who wasted them in attempts to sink destroyers would probably have been court-martialled.
But while the submarine had practically no means of successfully fighting the destroyer, the destroyer had several ways of putting an end to the submarine. The advantage which really made the destroyer so dangerous, as already intimated, was its excessive speed. On the surface the U-boat made little more than fifteen miles an hour, and under the surface it made little more than seven or eight. If the destroyer once discovered its presence, therefore, it could reach its prey in an incredibly short time. It could attack with its guns, and, if conditions were favourable, it could ram; and this was no trifling accident, for a destroyer going at thirty or forty miles could cut a submarine nearly in two with its strong, razor-like bow. In the early days of the war these were the main methods upon which it relied to attack, but by the time that I had reached London, another and much more frightful weapon had been devised. This was the depth charge, a large can containing about three hundred pounds of TNT, which, if it exploded anywhere within one hundred feet of the submarine, would either destroy it entirely or so injure it that the victim usually had to come to the surface and surrender.
I once asked Admiral Jellicoe who was the real inventor of this annihilating missile.
"No man in particular," he said. "It came into existence almost spontaneously, in response to a pressing need. Gunfire can destroy submarines when they are on the surface, but you know it can accomplish nothing against them when they are submerged. This fact made it extremely difficult to sink them in the early days of the war. One day, when the Grand Fleet was cruising in the North Sea, a submarine fired a torpedo at one of the cruisers. The cruiser saw the periscope and the wake of the torpedo, and had little difficulty in so manœuvring as to avoid being struck. She then went full speed to the spot from which the submarine had fired its torpedo, in the hope of ramming it. But by the time she arrived the submarine had submerged so deeply that the cruiser passed over her without doing her any harm. Yet the officers and crew could see the submerged hull; there the enemy lay in full view of her pursuers, yet perfectly safe! The officers reported this incident to me in the presence of Admiral Madden, second in command.