Total.
January 104,000 62,000 116,000 282,000 February 256,000 77,000 131,000 464,000 March 283,000 74,000 149,000 506,000 April 513,000 133,000 185,000 831,000 (The United States entered the war on April 6, 1917.) NOTE .-- In neither case is the loss of fishing craft included.
It will be realized that, since the losses towards the end of 1916 were such as to give just cause for considerable anxiety, the later figures made it clear that some method of counteracting the submarines must be found and found quickly if the Allied cause was to be saved from disaster.
None of the anti-submarine measures that had been under consideration or trial since the formation of the Anti-Submarine Division of the Naval Staff in December, 1916, could _by any possibility_ mature for some months, since time was necessary for the production of vessels and more or less complicated materiel, and in these circumstances the only step that could be taken was that of giving a trial to the convoy system for the ocean trade, although the time was by no means yet ripe for effective use of the system, by reason of the shortage of destroyers, sloops and cruisers, which was still most acute, although the situation was improving slowly month by month as new vessels were completed.
Prior to this date we had already had some experience of convoys as a protection against submarine attack.

The coal trade of France had been brought under convoy in March, 1917.

The trade between Scandinavia and North Sea ports was also organized in convoys in April of the same year, this trade having since December, 1916, been carried out on a system of "protected sailings." It is true that these convoys were always very much scattered, particularly the Scandinavian convoy, which was composed largely of neutral vessels and therefore presented exceptional difficulties in the matter of organization and handling.

The number of destroyers which could be spared for screening the convoys was also very small.

The protection afforded was therefore more apparent than real, but even so the results had been very good in reducing the losses by submarine attack.