The Allied navies were harrowing the submarines not only under the water and on the surface, but from the air. In the anti-submarine campaign the several forms of aircraft—airplane, seaplane, dirigible, and kite balloon—developed great offensive power. Nor did the fact that our fighters in the heavens made few direct attacks which were successful diminish the importance of their work. The records of the British Admiralty attribute the destruction of five submarines to the British air service; the French Admiralty gives the American forces credit for destroying one on the French coast. These achievements, compared with the tremendous efforts involved in equipping air stations, may at first look like an inconsiderable return; yet the fact remains that aircraft were an important element in defeating the German campaign against merchant shipping.
Like the subchaser and the submarine, the seaplane operated most successfully in coastal waters. I have already indicated that one advantage of the convoy system was that it forced the U-boats to seek their victims closer to the shore. In our several forms of aircraft we had still another method of interfering with their operation in such quarters. In order to use these agencies effectively we constructed aircraft stations in large numbers along the coast of France and the British Isles, assigned a certain stretch of coastline to each one of these stations, and kept the indicated area constantly patrolled. The advantages which were possessed by a fleet of aircraft operating at a considerable height above the water are at once apparent. The great speed of seaplanes in itself transformed them into formidable foes. The submarine on the surface could make a maximum of only 16 knots an hour, whereas an airplane made anywhere from 60 to 100; it therefore had little difficulty, once it had sighted the under-water boat, in catching up with it and starting hostilities. Its great speed also made it possible for an airplane or dirigible to patrol a much greater area of water than a surface or a subsurface vessel. An observer located several hundred feet in the heavens could see the submarine much more easily than could his comrades on other craft. If the water were clear he could at once detect it, even though it were submerged; in any event, merely lifting a man in the air greatly extended his horizon, and made it possible for him to pick up hostile vessels at a much greater distance. Moreover, the airplane had that same advantage upon which I have laid such emphasis in describing the anti-submarine powers of the submarine itself: that is, it was almost invisible to its under-water foe. If the U-boat were lying on the surface, a seaplane or a dirigible was readily seen; but if it were submerged entirely, or even sailing at periscope depth, the most conspicuous enemy in the heavens was invisible. After our submarines and our aircraft had settled down to their business of extermination, existence for those Germans who were operating in coastal waters became extremely hazardous and nerve-racking; their chief anxiety was no longer the depth bomb of a destroyer; they lived every moment in the face of hidden terrors; they never knew when a torpedo would explode into their vitals, or when an unseen bomb, dropped from the heavens, would fall upon their fragile decks.
I have said that the destructive achievements of aircraft figure only moderately in the statistics of the war; this was because the greater part of their most valuable work was done in co-operation with war vessels. Aircraft in the Navy performed a service not unlike that which it performed in the Army. We are all familiar with the picture of airplanes sailing over the field of battle, obtaining information which was wirelessed back to their own forces, "spotting" artillery positions, and giving ranges. The seaplanes and dirigibles of the Allied navies performed a similar service on the ocean. To a considerable extent they became the "eyes" of the destroyers and other surface craft, just as the airplanes on the land became the "eyes" of the army. As part of their equipment all the dirigibles had wireless telegraph and wireless telephone; as soon as a submarine was "spotted," the news was immediately flashed broadcast, and every offensive warship which was anywhere in the neighbourhood, as well as the airplane itself, started for the indicated scene. There are several cases in which the sinking of submarines by destroyers was attributed to information wirelessed in this fashion by American aircraft; and since the air service of the British navy was many times greater than our own, there are many more such "indirect sinkings" credited to the British effort.
The following citation, which I submitted to the Navy Department in recommending Lieutenant John J. Schieffelin for the Distinguished Service Medal, illustrates this co-operation between air and surface craft:
This officer performed many hazardous reconnaissance flights, and on July 9th, 1918, he attacked an enemy submarine with bombs and then directed the British destroyers to the spot, which were successful in seriously damaging the submarine. Again, on July 19th, 1918, Lieutenant Schieffelin dropped bombs on another enemy submarine, and then signalled trawlers to the spot, which delivered a determined attack against the submarine, which attack was considered highly successful and the submarine seriously damaged, if not destroyed. This officer was at all times an example of courageous loyalty.
Besides scouting and "spotting" and bombing, the aerial hunters of the submarine developed great value in escorting convoys. A few dirigibles, located on the flanks of a convoy, protected them almost as effectively as the destroyers themselves; and even a single airship not infrequently brought a group of merchantmen and troopships safely into port. Sometimes the airships operated in this way as auxiliaries to destroyers, while sometimes they operated alone. In applying this mechanism of protection to merchant convoys, we were simply adopting the method which Great Britain had been using for three years in the narrow passages of the English Channel. Much has been said of the skill with which the British navy transported about 20,000,000 souls back and forth between England and France in four years; and in this great movement seaplanes, dirigibles, and other forms of aircraft played an important part. In the same way this scheme of protection was found valuable with the coastal convoys, particularly with the convoys which sailed from one French port to another, and from British ports to places in Ireland, Holland, or Scandinavia. I have described the dangers in which these ships were involved owing to the fact that the groups were obliged to break up after entering the Channel and the Irish Sea, and thus to proceed singly to their destinations. Aircraft improved this situation to a considerable extent, for they could often go to sea, pick up the ships, and bring them safely home. The circumstance that our seaplanes, perched high in the air, could see the submarine long before they had reached torpedoing distance, and could, if necessary, signal to a destroyer for assistance, made them exceedingly valuable for this kind of work.
Early in 1918, at the request of the British Government, we took over a large seaplane base which had been established by the British at Killingholme, England, a little sea-coast town at the mouth of the Humber River. According to the original plan we intended to co-operate from this point with the British in a joint expedition against enemy naval bases, employing for this purpose especially constructed towing lighters, upon which seaplanes were to be towed by destroyers to within a short flying distance of their objectives. Although this project was never carried out, Killingholme, because of its geographical location, became a very important base for seaplanes used in escorting mercantile convoys to and from Scandinavian ports, patrolling mine-fields while on the lookout for enemy submarines and making those all-important reconnaissance flights over the North Sea which were intended to give advanced warning of any activity of the German High Seas Fleet. These flights lasted usually from six to eight hours; the record was made by Ensigns S. C. Kennedy and C. H. Weatherhead, U.S.N., who flew for nine hours continuously on convoy escort duty. For a routine patrol, this compares very favourably indeed with the flight of the now famous trans-Atlantic NC-4.
I can no better describe the splendid work of these enthusiastic and courageous young Americans than by quoting a few extracts from a report which was submitted to me by Ensign K. B. Keyes, of a reconnaissance flight in which he took part, while attached temporarily to a British seaplane station under post-graduate instruction. The picture given by Ensign Keyes is typical of the flights which our boys were constantly making:
On June 4, 1918, we received orders to carry out a reconnaissance and hostile aircraft patrol over the North Sea and along the coast of Holland. It was a perfect day for such work, for the visibility was extremely good, with a light wind of fifteen knots and clouds at the high altitude of about eight or ten thousand feet.
Our three machines from Felixstowe rose from the water at twelve o'clock, circled into patrol formation, and proceeded north-east by north along the coast to Yarmouth. Here we were joined by two more planes, but not without some trouble and slight delay because of a broken petrol pipe which was subsequently repaired in the air. We again circled into formation, Capt. Leckie, D.S.O., of Yarmouth, taking his position as leader of the squadron.