There were at times inevitable set-backs as the enemy gained experience of our methods, and new ones had then to be devised, and we were always most seriously handicapped by the strain imposed upon the Fleet by our numerous military and other commitments overseas, and by the difficulty of obtaining supplies of material, owing to the pre-occupation of our industries in meeting the needs of our Armies in equipment and munitions; but, generally speaking, it may be said that in April, 1917, the losses reached their maximum, and that from the following month and onwards the battle was being slowly but gradually won. By the end of the year it was becoming apparent that success was assured. The volume describes the changes carried out in the Admiralty Staff organization; the position of affairs in regard to submarine warfare in the early part of 1917; and the numerous anti-submarine measures which were devised and brought into operation during the year. The introduction and working of the convoy system is also dealt with. The entry of the United States of America into the war marked the opening of a new phase of the operations by sea, and it has been a pleasure to give particulars of our cordial co-operation with the United States Navy. The splendid work of the patrol craft and minesweepers is described all too briefly, and I have had to be content to give only a brief summary of the great services of the Dover and Harwich forces. Finally, an effort has been made to suggest the range and character of the work of the Production Departments at the Admiralty. It is impossible to tell this part of the story without conveying some suggestion of criticism since the output never satisfied our requirements. I have endeavoured also to indicate where it seemed to me that changes in organization were not justified by results, so that in future years we may benefit by the experience gained. But I would not like it to be thought that I did not, and do not, realize the difficulties which handicapped production, or that I did not appreciate to the full the work done by all concerned. It is unfortunate that attempts to draw attention to the lessons taught us by the war are regarded by many people either as complaints of lack of devotion to the country's interests on the part of some, or as criticisms of others who, in the years before the war or during the war, were responsible for the administration of the Navy. In anticipation of such an attitude, I wish to state emphatically that, where mention is made of apparent shortcomings or of action which, judged by results, did not seem, to meet a particular situation, this is done solely in order that on any future occasion of a similar character--and may the day be long postponed--the nation may profit by experience.