Thus we had to deal with an entirely new phase of the submarine campaign; the new conditions made it practicable to employ light vessels which existed in large numbers, and which could aggressively hunt out the submarines even though they were sailing submerged. The subchaser, when fitted with its listening devices, met these new requirements, though of course not to the desirable degree of precision we hoped soon to attain with still further improved hydrophones and larger vessels of the Eagle class then being built.

The matter was presented to the Allied Naval Council and, in accordance with the unanimous opinion of all of the members, they recommended that of the subchasers then available, a squadron should be based on Plymouth, where it could be advantageously used against the German submarines which were still doing great damage in the English Channel, and that another squadron, based on Queenstown, should similarly be used against the submarines in the Irish Sea.

I was therefore requested to concentrate the boats at these two points, and at once acquiesced in this recommendation.

But another point, widely separated from British waters, also made a powerful plea for consideration. In the Mediterranean the submarine campaign was still a menace. The spring and early summer of 1918 witnessed large losses of shipping destined to southern France, to Italy, and to the armies at Salonika and in Palestine. Austrian and German submarines, operating from their bases at Pola and Cattaro in the Adriatic, were responsible for this destruction. If we could pen these pests in the Adriatic, the whole Mediterranean Sea would become an unobstructed highway for the Allies. A glance at the map indicated the way in which such a desirable result might be accomplished. At its southern extremity the Adriatic narrows to a passage only forty miles wide—the Strait of Otranto—and through this restricted area all the submarines were obliged to pass before they could reach the water where they could prey upon Allied commerce. For some time before the Allied Naval Council began to consider the use of the American subchasers, the British navy was doing its best to keep submarines from passing this point. A defensive scheme known, not very accurately, as the "Otranto barrage" was in operation. The word "barrage" suggests an effective barrier, but this one at the base of the Adriatic consisted merely of a few British destroyers of ancient type and a large number of drifters, which kept up a continuous patrolling of the gateway through which the submarines made their way into the Mediterranean. It is no reflection upon the British to say that this barrage was unsatisfactory and inadequate, and that, for the first few months, it formed a not particularly formidable obstruction. So many demands were made upon the British navy in northern waters that it could not spare many vessels for this work; the Italian navy was holding the majority of its destroyers intact, momentarily prepared for a sortie by the Austrian battle fleet; the Otranto barrage, therefore, important as it was to the Allied cause, was necessarily insufficient. The Italian representatives at the Allied Council made a strong plea for a contingent of American subchasers to reinforce the British ships, and the British and French delegates seconded this request.

In the spring of 1918 I therefore sent Captain Leigh to southern Italy to locate and construct a subchaser base in this neighbourhood. After inspecting the territory in detail Captain Leigh decided that the Bay of Govino, in the island of Corfu, would best meet our requirements. The immediate connection which was thus established between New London and this ancient city of classical Greece fairly illustrates how widely the Great War had extended the horizon of the American people. There was a certain appropriateness in the fact that the American college boys who commanded these little ships—not much larger than the vessel in which Ulysses had sailed these same waters three thousand years before—should have made their base on the same island which had served as a naval station for Athens in the Peloponnesian War, and which, several centuries afterward, had been used for the same purpose by Augustus in the struggle with Antony. And probably the sight of the Achelleion, the Kaiser's palace, which was not far from this new American base, was not without its influence in constantly reminding our young men of the meaning of this unexpected association of Yankee-land with the ancient world.

III

By June 30, 1918, two squadrons of American chasers, comprising thirty-six boats, had assembled at Plymouth, England, under the command of Captain Lyman A. Cotten, U.S.N. The U.S. destroyer Parker, commanded by Commander Wilson Brown, had been assigned to this detachment as a supporting ship. The area which now formed the new field of operations was one which was causing great anxiety at that time. It comprehended that section of the Channel which reached from Start Point to Lizard Head, and included such important shipping ports as Plymouth, Devonport, and Falmouth. This was the region in which the convoys, after having been escorted through the submarine zone, were broken up, and from which the individual ships were obliged to find their way to their destinations with greatly diminished protection. It was one of the most important sections in which the Germans, forced to abandon their submarine campaign on the high seas, were now actively concentrating their efforts. Until the arrival of the subchasers sinkings had been taking place in these waters on a considerable scale. In company with a number of British hunting units, Captain Cotten's detachment kept steadily at work from June 30th until the middle of August, when it became necessary to send it elsewhere. The historical fact is that not a single merchant ship was sunk between Lizard Head and Start Point as long as these subchasers were assisting in the operations. The one sinking which at first seemed to have broken this splendid record was that of the Stockforce; this merchantman was destroyed off Dartmouth; but it was presently announced that the Stockforce was in reality a "mystery" ship, sent out for the express purpose of being torpedoed, and that she "got" the submarine which had ended her own career. This happening therefore hardly detracted from our general satisfaction over the work done by our little vessels. Since many ships had been sunk in this area in the month before they arrived, and since the sinkings started in again after they had left, the immunity which this region enjoyed during July and August may properly be attributed largely to the American navy. Not only were no bona-fide merchant ships destroyed, but no mines were laid from Start Point to Lizard Head during the time that the American forces maintained their vigil there. That this again was probably not a mere coincidence was shown by the fact that, the very night after these chasers were withdrawn from Plymouth, five mines were laid in front of that harbour, in preparation for a large convoy scheduled to sail the next day.

By the time that Captain Cotten's squadron began work the hunting tactics which had been developed during their training at New London had been considerably improved. Their procedure represented something entirely new in naval warfare. Since the chasers had to depend for the detection of the foe upon an agency so uncertain as the human ear, it was thought to be necessary, as a safeguard against error, and also to increase the chances of successful attack, that they should hunt in groups of at least three. The fight against the submarine, under this new system, was divided into three parts—the search, the pursuit, and the attack. The first chapter included those weary hours which the little group spent drifting on the ocean, the lookout in the crow's nest scanning the surface for the possible glimpse of a periscope, while the trained listeners on deck, with strange little instruments which somewhat resembled telephone receivers glued to their ears, were kept constantly at tension for any noise which might manifest itself under water. It was impossible to use these listening devices while the boats were under way, for the sound of their own propellers and machinery would drown out any other disturbances. The three little vessels therefore drifted abreast—at a distance of a mile or two apart—their propellers hardly moving, and the decks as silent as the grave; they formed a new kind of fishing expedition, the officers and crews constantly held taut by the expectation of a "bite." And frequently their experience was that of the proverbial "fisherman's luck." Hours passed sometimes without even the encouragement of a "nibble"; then, suddenly, one of the listeners would hear something which his experienced ear had learned to identify as the propellers and motors of a submarine. The great advantage possessed by the American tubes, as already said, was that they gave not only the sound, but its direction. The listener would inform his commanding officer that he had picked up a submarine. "Very faint," he would perhaps report, "direction 97"—the latter being the angle which it made with the north and south line. Another appliance which now rendered great service was the wireless telephone. The commanding officer at once began talking with the other two boats, asking if they had picked up the noise. Unless all three vessels had heard the disturbance, nothing was done; but if all identified it nearly simultaneously, this unanimity was taken as evidence that something was really moving in the water. When all three vessels obtained the direction as well as the sound it was a comparatively simple matter to define pretty accurately its location. The middle chaser of the three was the flagship and her most interesting feature was the so-called plotting-room. Here one officer received constant telephone reports from all three boats, giving the nature of the sounds, and, more important still, their directions. He transferred these records to a chart as soon as they came in, rapidly made calculations, and in a few seconds he was able to give the location of the submarine. This process was known as obtaining a "fix." The reports of our chaser commanders are filled constantly with reference to these "fixes"—the "fix" being that point on the surface of the ocean where three lines, each giving the direction of the detected sound, cross one another. The method can be most satisfactorily illustrated by the following diagram:

HOW THE LISTENING DEVICES LOCATED A SUBMARINE.