Among the minor lessons of the war, it will probably appear to most laymen that the unforeseen effectiveness of the submarine is the most significant. In a way this is true; but the significance of the lesson may be dangerously exaggerated unless we recognize the part contributed to the early successes of the submarine by the element of surprise to which allusion has already been made. When the war began, the submarine was an untried and an almost unknown weapon, and the British navy was rather contemptuous of it, or at least indifferent toward it. Its dramatic appearance in the North Sea at early dawn of a misty September morning was as great a surprise to the three British cruisers which it sank in rapid succession as the story of the disaster was to the world at large. The fact that the cruisers by their carelessness invited the fate which came to them does not, of course, deprive the incident of significance. But after all, the world has never doubted that a submarine could sink a ship that practically insisted upon being sunk.
As a result of this experience, British men-of-war operating thereafter in what they considered submarine territory, took reasonable precautions; and in such waters no other important successes have been scored against them. But neither to them nor, probably, to anyone else except their adversaries, did it occur that a submarine could make its way from the North Sea to the Dardanelles. And so it came about that when one of them appeared there, it found conditions again ideal for surprise, and taking advantage of these conditions delivered its attack and scored a success as striking as the earlier one in its own home waters.
The activities of submarines against merchant shipping we need not discuss here. The only lesson they hold for us, from the point of view of naval warfare, is the lesson that for them, as for all other activities of the submarine, there is an answer. The answer was not ready when the war began, but it was not long delayed. We are apt to think of the submarine as if it always operated under water, and completely under water. But when it is completely under water, it is completely blind and as helpless as other blind things are. To see objects at a distance, it must be on the surface, and to see them even close at hand it must at least expose its periscope. Having definitely located an object within easy range, it may wholly submerge and deliver its torpedo without seeing the target. But the chance of a hit under these conditions is remote. Normally the submarine remains on the surface until it sights an enemy. Having approached as close as seems practicable without danger of being seen itself, it submerges, except for the periscope, and approaches within range, directing its course and its aim, by sight—not by some occult instinct such as is often attributed to it. When within a zone where imminent danger threatens, it may remain wholly submerged for a long period of time, but when so submerged, it is not in any degree a threat to other craft.
In other words, the submarine is dangerous only when it can see. And when it can see, it can be seen—not easily perhaps, but certainly by an observer reasonably close at hand and on the lookout. It is especially liable to detection from an airship. Moreover, the noise of its propellers can be heard at a considerable distance, and a very sensitive microphone has been developed as a submarine detector. The waters about Great Britain are now patrolled by hundreds of small, fast craft—destroyers, trawlers, motor boats—always on the lookout for a periscope or other indication of the proximity of a submarine. If one is actually seen, its capture or destruction follows as a matter of course. If the presence of one is indicated by the microphone or other evidence, such as oil floating on the water, or bubbles rising to the surface, nets are lowered and the water dragged for miles around. It is not known how many submarines have been destroyed by these tactics, but the number is unquestionably large. Thus the submarine is being robbed of much of its mystery and much of its terror, and while it remains, and will always remain, a danger, the lesson of the war is that it must take its place beside other dangers with which modern war is filled, as something to be respected and feared, but not as having rendered the battleship and battle cruiser obsolete.
Another lesson of the war has resulted from the fact that practically all of the important operations on the British side have been conducted by battle cruisers, not by battleships. It is not to be understood from this that the battleship has been discredited, for such is not the case. The fleet to which reference has already been made as holding the gates of the North Sea and "containing" the German fleet behind the fortifications of Helgoland is made up principally of battleships, and it is largely because they have been engaged in this important duty that the few opportunities which the war has offered for active service have fallen to the lot of battle cruisers. But there are other reasons for this which spring from the nature of the battle cruiser itself and inhere in the difference between this type and the battleship. In size the types are practically identical, and in power of armament the difference is not great. But the battle cruiser sacrifices much of the armor by which the battleship is weighted down, and purchases by this sacrifice a great increase in speed. The typical battleship of to-day has some 14 inches of armor on the side; the battle cruiser, from 5 to 9 inches. The battleship has 22 knots speed, the battle cruiser 32 knots. There has been much discussion as to the relative merits of the two types, and conservative officers have been slow to accept the battle cruiser. The war has shown the necessity for both types, and no better illustration of their relative merits could be wished than that which is afforded by the spectacle of the battleships engaged in what is practically a blockade of the German fleet, while the battle cruisers have swept the German raiders, the Scharnhorst, Gneisenau, and their consorts, from the distant seas which were the chosen field of their operations. Following the destruction of Admiral Cradock's little squadron by the faster and more heavily armed Scharnhorst and Gneisenau, the British admiralty dispatched a squadron of battle cruisers to run down the German ships, and in the battle off the Falkland Islands the history of Coronel was repeated with a change of sides, the fast and heavily armed battle cruisers under Admiral Sturdee making short work of the German ships, which they overmatched in speed and range as decisively as the Germans had overmatched the ships of Admiral Cradock's squadron at Coronel. In each case victory went to the ships of high speed and long-range guns, and these two are the determining characteristics of the battle cruiser. In the action of January 25, 1915, in the North Sea, the same characteristics won again. Battle cruisers were engaged on both sides, but the side which had the advantage in speed and range won the fight.
Thus the battle cruiser had justified itself, and its justification is one of the striking lessons of the war. We may believe that the lesson will be emphasized if the time ever comes when this type finds the opportunity to display its adaptability for work in certain other fields for which it was originally designed—in scouting operations, for example, and in flanking movements in connection with a fleet engagement.
It does not appear that aeroplanes were used for scouting in any of the operations in the open sea—either as preliminary to the battle off Coronel and the Falklands, or in the search for raiders like the Emden and the Karlsruhe. They have been used, however, in the waters about the British Islands, and with such marked success as to leave no doubt that they would have been of great value in search operations on a larger scale. They were used also for directing the fire of ships on the fortifications at the Dardanelles, and the results indicate that they have an important field of usefulness for directing the fire of one ship or fleet against another. It is to be expected that from this time forward, vessels fitted for carrying and launching both air and water planes will accompany fleets, and it is impossible to think of a scout to be designed after the lessons of this war, which will not carry several of them. As the scouts are the eyes of the fleet, so the aeroplanes will be the eyes of the scouts, extending the scouting range by several hundred miles and making secrecy of operations at sea almost as impossible as they have already made it on land.
Allusion has already been made to the use of aeroplanes—flying not more than a few hundred feet above the water—for locating submarines; and it is not difficult to understand how effective a waterplane would be for destroying a periscope, or even a submarine itself—this last, perhaps, by dropping a bomb.
The lesson of the torpedo is connected with that of the submarine, but has many features which are individual to itself. It is known that within a very few years past the range and accuracy of the torpedo have greatly increased, but there is little evidence connecting these features with the performance of torpedoes in the present war. So far as known, the submarines have done most of their effective work at short ranges where hits were to be expected. And no one will ever know how many shots have missed. The great outstanding lesson thus far is the extraordinary destructiveness of the torpedoes that have found their mark. It would never have been believed two years ago that ships like the Cressy, Aboukir, and Hogue would turn turtle a few minutes after a single blow from a torpedo. Still less would it have seemed possible to sink a Lusitania in fifteen minutes. A torpedo might, of course, produce an extraordinary effect if it chanced to strike a boiler compartment or a magazine. But it does not appear that this happened in any one of the many disasters in question. It has been said that the German torpedoes carry an exceptionally heavy explosive charge, the extra weight having been gained by a sacrifice in speed and range. This may in part explain their effectiveness, but when all allowance is made for what we know or guess along this and similar lines, the fact remains that the torpedo has shown itself a weapon of vastly greater destructive power than the world has heretofore attributed to it.
The story of the Dardanelles campaign has illustrated again the futility of attacking land fortifications by battleships. Attacks of this kind have never succeeded, and the temptation is strong to accept the theory that in planning these operations the British anticipated little or no resistance from those in command of the forts. It was conceivable that the forts could be passed—as were those at New Orleans and Mobile Bay by Farragut—but not that they could be reduced by the gun fire of ships. Information is lacking as to the damage actually done. It was probably greater than the defenders have admitted; but it evidently fell far short of silencing the forts. If the world needed a new demonstration of the power of forts to stand out against ships, we may put this down as one more lesson of the war.