It was not the simplest thing to pilot a submarine out of its base. The Allies were constantly laying mines at these outlets; and before the U-boat could safely make its exit elaborate sweeping operations were necessary. It often took a squadron of nine or ten surface ships, working for several hours, to manoeuvre a submarine out of its base and to start it on its journey. For these reasons we could keep a careful watch upon its movements; we always knew when one of our enemies came out; we knew which one it was, and not infrequently we had learned the name of the commander and other valuable details. Moreover, we knew where it went, and we kept charts on which we plotted from day to day the voyage of each particular submarine.
"Why didn't you sink it then?" is the question usually asked when I make this statement a question which, as I shall show, merely reflects the ignorance which prevails everywhere on the underlying facts of submarine warfare.
Now in this densely packed shipping area, which extended from the north of Ireland to Brest, there were seldom more than eight or ten submarines engaged in their peculiar form of warfare at one time. The largest number which I had any record of was fifteen; and this was an exceptional force; the usual number was four, six, eight, or perhaps ten. Yet the men upon our merchant convoys and troopships saw submarines scattered all over the sea. We estimated that the convoys and troopships reported that they had sighted about 300 submarines for every submarine which was actually in the field. Yet we knew that for every hundred submarines which the Germans possessed they could keep only ten or a dozen at work in the open sea. The rest were on their way to the hunting grounds, or returning, or they were in port being refitted and taking on supplies. Could Germany have kept fifty submarines constantly at work on the great shipping routes in the winter and spring of 1917 before we had learned how to handle the situation nothing could have prevented her from winning the war. Instead of sinking 850,000 tons in a single month, she would have sunk 2,000,000 or 3,000,000 tons. The fact is that Germany, with all her microscopic preparations for war, neglected to provide herself with the one instrumentality with which she might have won it.
This circumstance, that so few submarines could accomplish such destructive results, shows how formidable was
