CHAPTER II
THE SUBMARINE CAMPAIGN IN THE EARLY PART OF 1917
Table of Contents The struggle against the depredations of the enemy submarines during the year 1917 was two-fold; offensive in the direction of anti-submarine measures (this was partly the business of the Anti-Submarine Division of the Naval Staff and partly that of the Operations Division); defensive in the direction of protective measures for trade, whether carried in our own ships or in ships belonging to our Allies or to neutrals, this being the business of the Trade and Mercantile Movements Divisions.
Prior to the formation of the Mercantile Movements Division the whole direction of trade was in the hands of the Trade Division of the Staff.
The difficulty with which we were constantly faced in the early part of 1917, when the effective means of fighting the submarine were very largely confined to the employment of surface vessels, was that of providing a sufficient number of such vessels for offensive operations without incurring too heavy risks for our trade by the withdrawal of vessels engaged in what might be termed defensive work. There was always great doubt whether any particular offensive operation undertaken by small craft would produce any result, particularly as the numbers necessary for success were not available, whilst there was the practical certainty that withdrawal of defensive vessels would increase our losses; the situation was so serious in the spring of 1917 that we could not carry out experiments involving grave risk of considerably increased losses.
On the other hand, the sinking of one enemy submarine meant the possible saving of a considerable number of merchant ships. It was difficult to draw the line between the two classes of operations.
The desire of the Anti-Submarine Division to obtain destroyers for offensive use in hunting flotillas in the North Sea and English Channel led to continual requests being made to me to provide vessels for the purpose. I was, of course, anxious to institute offensive operations, but in the early days of 1917 we could not rely much on depth-charge attack, owing to our small stock of these charges, and my experience in the Grand Fleet had convinced me that for success in the alternative of hunting submarines for a period which would exhaust their batteries and so force them to come to the surface, a large number of destroyers was required, unless the destroyers were provided with some apparatus which would, by sound or otherwise, locate the submarine. This will be realized when the fact is recalled that a German submarine could remain submerged at slow speed for a period which would enable her to travel a distance of some 80 miles. As this distance could be covered in any direction in open waters such as the North Sea, it is obvious that only a very numerous force of destroyers steaming at high speed could cover the great area in which the submarine might come to the surface. She would, naturally, select the dark hours for emergence, as being the period of very limited range of vision for those searching for her. In confined waters such as those in the eastern portion of the English Channel the problem became simpler. Requests for destroyers constantly came from every quarter, such as the Commanders-in-Chief at Portsmouth and Devonport, the Senior Naval Officer at Gibraltar, the Vice-Admiral, Dover, the Rear-Admiral Commanding East Coast, and the Admiral at Queenstown. The vessels they wanted did not, however, exist.
Eventually, with great difficulty, a force of six destroyers was collected from various sources in the spring of 1917, and used in the Channel solely for hunting submarines; this number was really quite inadequate, and it was not long before they had to be taken for convoy work.
Evidence of the difficulty of successfully hunting submarines was often furnished by the experiences of our own vessels of this type, sometimes when hunted by the enemy, sometimes when hunted in error by our own craft. Many of our submarines went through some decidedly unpleasant experiences at the hands of our own surface vessels and occasionally at the hands of vessels belonging to our Allies. On several such occasions the submarine was frequently reported as having been sunk, whereas she had escaped.
As an example of a submarine that succeeded not only in evading destruction, but in getting at least even with the enemy, the case of one of our vessels of the "E" class, on patrol in the Heligoland Bight, may be cited. This submarine ran into a heavy anti-submarine net, and was dragged, nose first, to the bottom. After half an hour's effort, during which bombs were exploding in her vicinity, the submarine was brought to the surface by her own crew by the discharge of a great deal of water from her forward ballast tanks. It was found, however, that the net was still foul of her, and that a Zeppelin was overhead, evidently attracted by the disturbance in the water due to the discharge of air and water from the submarine. She went to the bottom again, and after half an hour succeeded in getting clear of the net. Meanwhile the Zeppelin had collected a force of trawlers and destroyers, and the submarine was hunted for fourteen hours by this force, assisted by the airship. During this period she succeeded in sinking one of the German destroyers, and was eventually left unmolested.
For a correct appreciation of submarine warfare it is necessary to have a clear idea of the characteristics and qualities of the submarine herself, of the numbers possessed by the enemy, and of the rate at which they were being produced. It is also necessary, in order to understand the difficulty of introducing the counter measures adopted by the Royal Navy, to know the length of time required to produce the vessels and the weapons which were employed or which it was intended to employ in the anti-submarine war.
The German submarines may be divided into four classes, viz.: Submarine cruisers, U-boats, U.B.-boats, U.C.-boats. There were several variations of each class.
The earlier submarine cruisers of the "Deutschland" class were double-hulled vessels, with a surface displacement of 1,850 tons, and were about 215 feet long; they had a surface speed of about 12 knots and a submerged speed of about 6 knots. They carried two 5.9-inch guns, two 22 pounders, two torpedo tubes, and 12 torpedoes. They could keep the sea for quite four months without being dependent on a supply ship or base.
The later submarine cruisers were double-hulled, 275-320 feet long, had a surface speed of 16-18 knots, and a submerged speed of about 7 to 8 knots. They carried either one or two 5.9-inch guns, six torpedo tubes, and about 10 torpedoes. They had a very large radius of action, viz., from 12,000 to 20,000 miles, at a speed of 6 knots. A large number (some 30 to 40) of these boats were under construction at the time of the Armistice, but very few had been completed.
There were two or three types of U-boats. The earlier vessels were 210 to 220 feet long, double-hulled, with a surface displacement of about 750 tons, a surface speed of 15 to 16 knots, and a submerged speed of about 8 knots. They carried one or two 4.1-inch guns, four to six torpedo tubes, and about 10 torpedoes.
Later vessels of the class were 230 to 240 feet long, and of 800 to 820 tons surface displacement, and carried six torpedo tubes and 16 torpedoes. Some of them, fitted as minelayers, carried 36 mines, and two torpedo tubes, but only two torpedoes. A later and much larger class of minelayers carried a 5.9-inch gun, four torpedo tubes, 42 mines, and a larger number of torpedoes. The earlier U-boats could keep the sea for about five weeks without returning to a base or a supply ship; the later U-boats had much greater sea endurance.
The smaller U.B.-boats were single-hulled, and about 100 feet long, had a surface speed of 7 to 9 knots and a submerged speed of about 5 knots, and carried one 22-pounder gun, two torpedo tubes and four torpedoes. These boats could keep the sea for about two weeks without returning to a base or supply ship. A later class were double-hulled, 180 feet long, with greater endurance (8,000 miles at 6 knots), a surface speed of 13 knots and a submerged speed of 8 knots; they carried one 4.1-inch gun, five tubes and 10 torpedoes.
The earliest U.C.-boats were 111 feet long, with a surface displacement of 175 tons, a surface speed of 6-½ knots, and a submerged speed of 5 knots. They carried 12 mines, but no torpedo tubes, and as they had a fuel endurance of only 800 miles at 5-½ knots, they could operate only in southern waters.
The later U.C.-boats were 170 to 180 feet long, double-hulled, had a surface speed of 11 to 12 knots and a submerged speed of about 7 knots, carried 18 mines, three torpedo tubes, five torpedoes, and one 22-pounder gun, and their fuel endurance was 8,000 to 10,000 miles at a speed of 7 to 8 knots.
At the end of February, 1917, it was estimated that the enemy had a total of about 130 submarines of all types available for use in home waters, and about 20 in the Mediterranean. Of this total an average of between one-half and one-third was usually at sea. During the year about eight submarines, on the average, were added monthly to this total. Of this number some 50 per cent, were vessels of the mine-laying type.
All the German submarines were capable of prolonged endurance submerged. The U-boats could travel under water at the slowest speed for some 48 hours, at about 4 knots for 20 hours, at 5 knots for about 12 hours, and at 8 knots for about 2 hours.
They were tested to depths of at least 180 feet,...
