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610 still in use in the early part of 1918. From first to last it achieved the destruction of 13 submarines with the loss of some 20 decoy ships, great and small, some like the " Prize " and " Vala " with all hands. Its place was now taken by the seaplane and P boat. The latter were low boats not easily seen in mist or at dawn and were responsible for no less than four submarines in 1917. Aircraft now began to be really effective, and in 1917 six submarines succumbed to the 3co-lb. bombs of large Handley- Pages in the southern portion of the North Sea. British sub- marines too were constantly on patrol, and were able to count six submarines to their credit by the end of the year (Gi3 sank UC43 off the Shetlands March 10; 54 U8i in the Atlantic May i ; D? U45 north of Ireland Sept. 12; 45 UC79, Oct. 19; 52 UC63 Nov. i, in the North Sea, and 15 UC6s Nov. 3, in the Chan- nel). The hydrophone, an instrument designed to detect sub- marines by sound waves under water, also developed greatly, but was more useful as a detector and in controlled minefields than in actual pursuit.

The whole system of staff work was overhauled. Direction of convoys became one of the principal functions of the naval staff and the machinery of Intelligence was adjusted in this light. Intelligence of first-rate importance derived from wireless di- rectionals had hitherto been shrouded in secrecy and locked away in drawers for the edification of the very few. The director of Naval Intelligence (Rear-Adml. Sir W. R. Hall) at last obtained control of it, and spread it abroad and circulated it to every command. The movements of all enemy submarines hitherto veiled in secrecy were displayed on a great chart in the Convoy room, and subjected to careful analysis by the new Plans Section. In Oct. 1917 this division prepared a large mine-net operation based on careful observation of submarine tracks in September. In spite of bad weather and unfavourable circumstances three large submarines (Uso, U66 and Uio6) found their way into the minefield and were sunk, causing a scare in the Bight which sent submarines round by the Kattegat for the first time.

Plans were prepared too for mining the Bight, but it was not till Sept. 1917 that the new mines were ready in sufficient quan- tity. Gradually the whole strength of the High Sea fleet had to be concentrated on getting submarines in and out. An armada of minesweepers, barrier breakers, escort forces and outpost forces were constantly at work trying to keep a passage open for them along ways which extended as far as 150 m. from Heligoland. Dover still remained a thorn in the flesh. The cessation of sub- marine activity in April 1916 had been erroneously attributed there to the Belgian coast barrage, and a similar barrage had accordingly been laid across the Straits in the latter part of 1916. It was composed of mine-nets 60 ft. deep with a minefield in support. But the mines were of the old defective design. They dragged into the nets, sank British ships, and had to be swept up in June and July 1917. The barrage entailed enormous labour but did not close the Straits, and from Feb. to Nov. 1917 enemy submarines passed at the rate of at least 24 passages a month. This was a serious matter, for the Dover passage saved a Flanders boat eight days on the double journey to the Channel approach out of its trip of 14 days, and a Bight boat six days out of its trip of 25 days. In Oct. the whole question became acute, for Flan- ders boats were responsible for some 22 ships a month in the Channel. The proper antidote was a strong minefield, and the vice-admiral at Dover had suggMtod in July 1917 laying a deep minefield from the Varne to Gris Nez, but the new mines were not ready and could not be supplied to Dover till Nov. It was partly laid on Nov. 21, but it was not constantly and intensively patrolled so as to make the submarines dive, with the result that between Nov. 21 and Dec. 821 submarines made the passage in safety. This was a severe disappointment, and instructions were sent to establish a strong patrol equipped with flares and search- lights to force the submarines down. This was done to a limited extent, and on the igth the new minefield took its first toll in UBs6. But difficulties arose in the execution of the plans and the urgency was so acute that before the end of the month Rear- Adml. Sir Roger Keyes, Director of Plans, was sent to Dover to assume the command, and the next four months saw nine sub-

marines destroyed in the Dover area. By Feb. 1918 the Bight boats had ceased to use the Straits, and by May the activity of the Flanders boats in the Channel had been enormously reduced; the blocking of Zeebrugge contributed to this result, and the losses in the Channel were reduced to six a month, the minefields laid by the Flanders boats falling from 404 in 1917 to 64 in 1918.

The year 1918 saw the commencement of a much more am- bitious scheme the Northern Barrage which aimed at nothing less than mining with 120,000 mines the huge stretch of 240 m. between the Orkneys and Norway. (See MINESWEEPING AND MINELAYING.) This was really an immense task, complicated by a deep gut some 60 m. wide on the Norwegian side where the depths ran to 150 fathoms. The credit for its conception and execution lies largely with Adml. Sims and the U.S. navy. It was an American enterprise performed by American sailors in American minelayers. As it was only commenced in April and was barely completed in Oct. its value is difficult to appraise, but the loss of some half-a-dozen boats can be attributed to it in Sept. and Oct. 1918. United States destroyers too were doing invaluable work in escorting convoys, and had been doing it ever since May 1917, during the dark months of 1917 when destroyers were more valuable than battleships.

The losses in the Mediterranean had given rise to serious con- cern, and the First Lord (Sir Eric Geddes) and the director of Naval Intelligence proceeded there in person to arrange for an extensive reorganization of the commander-in-chief's staff. Its clear waters, too deep for mines, and its regular tracks had been an ideal hunting ground for submarines. During 1917 only two German submarines had been lost there, and in the black month of April 1917 the Mediterranean had supplied one-fifth of the tonnage sunk. The arrival of some 14 Japanese destroyers in the summer brought the losses down about 10%, but in Dec. 1917, when vigorous action had greatly reduced the losses at home, the Mediterranean was still contributing 147,000 tons a month or, over one-third of the whole. The convoy system was now intro-' duced in the Mediterranean, the Otranto barrage was estab- lished and reinforced, and in May 1918 no fewer than four sub- marines were destroyed there. The effect of these measures was soon felt. Our losses in that sea were reduced from 95 ships a month in the last quarter of 1917 to an average of 43 in July, Aug. and Sept. 1918.

The U-boat zone had been extended to the Azores in Nov. 1917, and one or two boats had been working regularly there with fair results and comparative immunity till May n 1918 when UiS4was torpedoed by 35 about 150 m. west of Cape St. Vincent, an exploit directly due to improved intelligence.

Adml. von Capclle had been confident that his submarines would be able to prevent the U.S.A. troops reaching Europe, but actually not a single transport was lost up to Feb. 5 1918, when the " Tuscania " was torpedoed with a loss of only 44 lives out of 2,404. To stop the ceaseless flow of troops four large sub- marines were sent across the Atlantic, but though they destroyed over 60 ships they did not get a single loaded transport, and Uis6 was lost in the Northern Barrage on her way home. On July 19 1918 the great liner " Justicia," 32,234 tons, was hit by a torpedo from UB64 at 2:30 P.M. off the Skerryvore (Scotland, W. coast), and attacked again by U54 and UBi24 the next morning. A whole armoury of depth charges was dropped round UBi24 by the " Marne " and other destroyers, forcing her to the sur- face to surrender. All this time the mining of the Heligoland Bight went steadily on with the help of the gallant 2oth Destroyer Flotilla (Capt. Berwick Curtis), and its exits were occasionally entirely closed. The Flanders flotilla felt the full force of the increased activity at Dover and suffered heavily. In Jan. 1918 it numbered 29 boats; it lost no less than 24 during the year and its strength dropped to 13. By the middle of 1918 it had earned the dread name of the " Drowning Flotilla," and its boats could reckon on a life of only three or four trips.

The Kattegat still remained open. In April 1918 a deep minefield was laid there, and had it been possible to keep it patrolled the submarines would have had to face another serious danger. How far this was practicable is a moot point.