Those who are inclined to indulge in criticism should ever bear in mind that the Navy was faced with problems which were never foreseen, and could not have been foreseen, by anyone in this country. Who, for instance, would have ever had the temerity to predict that the Navy, confronted by the second greatest Naval Power in the world, would be called upon to maintain free communications across the Channel for many months until the months became years, in face of the naval forces of the enemy established on the Belgian coast, passing millions of men across in safety, as well as vast quantities of stores and munitions? Who would have prophesied that the Navy would have to safeguard the passage of hundreds of thousands of troops from the Dominions to Europe, as well as the movement of tens of thousands of labourers from China and elsewhere? Or who, moreover, would have been believed had he stated that the Navy would be required to keep open the sea communications of huge armies in Macedonia, Egypt, Palestine, Mesopotamia and East Africa, against attack by surface vessels, submarines and mines, whilst at the same time protecting the merchant shipping of ourselves, our Allies, and neutral Powers against similar perils, and assisting to ensure the safety of the troops of the United States when they, in due course, were brought across the Atlantic? Compare those varied tasks with the comparatively modest duties which in pre-war days were generally assigned to the Navy, and it will be seen how much there may be to learn of the lessons of experience, and how sparing we should be of criticism. Wisdom distilled from events which were unforeseeable should find expression not in criticisms of those who did their duty to the best of their ability, but in the taking of wise precautions for the future. Little mention is made in this volume of the work of the Grand Fleet during the year 1917, but, although that Fleet had no opportunity of showing its fighting power, it must never be forgotten that without the Grand Fleet, under the distinguished officer who succeeded me as Commander-in-Chief at the end of 1916, all effort would have been of no avail, since every operation by sea, as well as by land, was carried out under the sure protecting shield of that Fleet, which the enemy could not face. I am conscious of many shortcomings in the book, but it may prove of interest to those who desire to know something of the measures which gradually wore down the German submarine effort, and, at any rate, it is the only record likely to be available in the near future of the work of fighting the submarines in 1917. June, 1920. CHAPTER I ADMIRALTY ORGANIZATION; THE CHANGES IN 1917