For the British navy it was therefore a matter of choice what areas she would attempt to protect with her destroyer forces; the one thing that was painfully apparent was that she could not satisfactorily safeguard all the danger zones. With the inadequate force at her disposal it was inevitable that certain areas should be left relatively open to the U-boats; and the decision as to which ones these should be was simply a matter of balancing the several conflicting interests. In April, 1917, the Admiralty had decided to give the preference to the Grand Fleet, the hospital ships, the Channel crossing, and the Mediterranean, practically in the order mentioned. It is evident from these facts that nearly the entire destroyer fleet must have been disposed in these areas. This decision, all things considered, was the only one that was possible; yet, after placing the destroyers in these selected areas, the great zone of trans-Atlantic shipping, west and south of Ireland, vitally important as it was, was necessarily left inadequately protected. So desperate was the situation that sometimes only four or five British destroyers were operating in this great stretch of waters; and I do not think that the number ever exceeded fifteen. Inasmuch as that represented about the number of German submarines in this same area, the situation may strike the layman as not particularly desperate. But any such basis of comparison is absurd. The destroyers were operating on the surface in full view of the submarines; the submarines could submerge at any time and make themselves invisible; and herein we have the reason why the contest was so markedly unequal. But aside from all other considerations, the method of warfare adopted by the Allies against the U-boat was necessarily ineffective, but was the best that could be used until sufficient destroyers became available to convoy shipping. The so-called submarine patrol, under the circumstances which prevailed at that time, could accomplish very little. This little fleet of destroyers was based on Queenstown; from this port they put forth and patrolled the English Channel and the waters about Ireland in the hope that a German submarine would stick its nose above the waves. The central idea of the destroyer patrol was this one of hunting; the destroyer could have sunk any submarine or driven it away from shipping if the submarine would only have made its presence known. But of course this was precisely what the submarine declined to do. It must be evident to the merest novice that four or five destroyers, rushing around hunting for submarines which were lying a hundred feet or so under water, could accomplish very little. The under-water boat could always see its surface enemy long before it was itself seen and thus could save its life by the simple process of submerging. It must also be clear that the destroyer patrol could accomplish much only in case there were a very large number of destroyers.