British anti-submarine measures were almost non-existent at the commencement of the war.  Sir Arthur Wilson, when in command of the Channel Fleet in the early days of the submarine, had experimented with nets as an anti-submarine measure, and shortly before the war submarines were exercised at stalking one another in a submerged condition; also the question of employing a light gun for use against the same type of enemy craft when on the surface had been considered, and some of our submarines had actually been provided with such a gun of small calibre.  Two patterns of towed explosive sweeps had also been tried and adopted, but it cannot be said that we had succeeded in finding any satisfactory anti-submarine device, although many brains were at work on the subject, and therefore the earliest successes against enemy submarines were principally achieved by ramming tactics.  Gradually other devices were thought out and adopted; these comprised drift and stationary nets fitted with mines, the depth charge, decoy ships of various natures, gunfire from patrol craft and gunfire from armed merchant ships, as well as the numerous devices mentioned in Chapter III.

Except at the very commencement of the war, when production of craft in Germany was slow, presumably as a result of the comparatively small number under construction when war broke out, the British measures failed until towards the end of 1917 in sinking submarines at a rate approaching in any degree that at which the Germans were producing them.

Thus Germany started the war with 28 submarines; five were added and five were lost during 1914, leaving the number still 28 at the commencement of 1915.

During 1915, so far as our knowledge went, 54 were added and only 19 were lost, the total at the commencement of 1916 being therefore 63.

During 1916 it is believed that 87 submarines were added and 25 lost, leaving the total at the commencement of 1917 at 125.

During 1917 our information was that 78 submarines were added and 66 lost, leaving the total at the end of the year at 137.

The losses during 1917, given quarterly, indicate the increasing effectiveness of our anti-submarine measures.  These losses, so far as we know them, were: 

First quarter ... 10 Third quarter ... 20
Second quarter ... 12 Fourth quarter ... 24

During 1918, according to Admiral Scheer ("Germany’s High Sea Fleet In the World War,” page 335), 74 submarines were added to the fleet in the period January to October.  The losses during this year up to the date of the Armistice totalled 70, excluding those destroyed by the Germans on the evacuation of Bruges and those blown up by them at Pola and Cattaro.  Taken quarterly the losses were: 

First quarter ... 18 Third quarter ... 21
Second quarter ... 26 Fourth quarter (to
                        date of Armistice) ... 6

It will be seen from the foregoing figures for 1917 and 1918 that the full result of the anti-submarine measures inaugurated in 1917 and previous years was being felt in the last quarter of 1917, the results for 1918 being very little in advance of those for the previous half-year.