When it became possible to adopt the system of bringing merchant ships in convoys through the submarine zone under the escort of a screen of destroyers, this system became in itself, to a certain extent, an offensive operation, since it necessarily forced the enemy submarines desirous of obtaining results into positions in which they themselves were open to violent attack by depth charges dropped by destroyers.

During the greater part of the year 1917, however, it was only possible to supply destroyers with a small number of depth charges, which was their principal anti-submarine weapon; as it became feasible to increase largely the supply of these charges to destroyers, so the violence of the attack on the submarines increased, and their losses became heavier.

The position then, as it existed in the early days of the year 1917, is described in the foregoing remarks.

The result measured in loss of shipping (British, Allied, and neutral) from submarine and mine attack in the first half of the year was as follows in gross tonnage: 

January — 324,016
February — 500,573
March — 555,991
April — 870,359
May — 589,754
June — 675,154

Because of the time required for production, it was a sheer impossibility to put into effect any fresh devices that might be adopted for dealing with submarine warfare for many months, and all that could be done was to try new methods of approach to the coast and, as the number of small craft suitable for escort duty increased, to extend gradually the convoy system already in force to a certain extent for the French coal trade and the Scandinavian trade.

In the chapters which follow the further steps which were taken to deal with the problem, and the degree of success which attended them, will be described.

CHAPTER III

ANTI-SUBMARINE OPERATIONS

The previous chapters have dealt with the changes in organization carried out at the Admiralty during the year 1917 largely with the object of being able to deal more effectively with the submarine warfare against merchant ships.  Mention has also been made of the submarine problem with which the Navy had to deal; particulars of the anti-submarine and other work carried out will now be examined.

A very large proportion of the successful anti-submarine devices brought into use during 1917, and continued throughout the year 1918, were the outcome of the work of the Anti-Submarine Division of the Naval Staff, and it is but just that the high value of this work should be recognized when the history of the war comes to be written by future historians.  As has been stated in Chapter I, Rear-Admiral A.C.  Duff, C.B., was the original head of the division, with Captain F.C.  Dreyer, C.B., Commander Yeats Brown, and Commander Reginald Henderson as his immediate assistants.