dozens of hostile U-boats were preying upon our commerce and threatening our shores. These submarines, however, attacked almost exclusively sailing vessels and small coastwise steamers, rarely, if ever, using torpedoes. A number of mines were laid at different points off our ports, on what the Germans believed to be the traffic routes; but the information which we had concerning them made it possible to counter successfully their efforts and, from a military point of view, the whole of the submarine operations off our coast can be dismissed as one of the minor incidents of the war, as the Secretary of the Navy described it in his Annual Report. The five submarines sunk in all approximately 110,000 tons of shipping, but the vessels were, for the most part, small and of no great military importance. The only real victory was the destruction of the cruiser _San Diego_, which was sunk by a mine which had been laid by the _U-156_ off Fire Island. CHAPTER XI FIGHTING SUBMARINES FROM THE AIR 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.