Germany's purpose in adopting the ruthless submarine warfare was, of course, the one which I have indicated: to deprive the Allied armies in the field, and their civilian populations, of these supplies from overseas which were essential to victory. Nature had been kind to this German programme when she created the British Isles. Indeed this tight little kingdom and the waters which surround it provided an ideal field for operations of this character. For purposes of contrast, let us consider our own geographical situation. A glance at the map discloses that it would be almost impossible to blockade the United States with submarines. In the first place, the operation of submarines more than three thousand miles from their bases would present almost insuperable difficulties. That Germany could send an occasional submarine to our coasts she demonstrated in the war, but it would be hardly possible to maintain anything like a regular and persistent campaign. Even if she could have kept a force constantly engaged in our waters, other natural difficulties would have defeated their most determined efforts. The trade routes approach our Atlantic sea-coast in the shape of a fan, of which different sticks point to such ports as Boston, New York, Philadelphia, Norfolk, and the ports of the Gulf of Mexico. To destroy shipping to American ports it would be necessary for the enemy to cover all these routes with submarines, a project which is so vast that it is hardly worth the trial. In addition we have numerous Pacific ports to which we could divert shipping in case our enemy should attempt to blockade us on the Atlantic coast; our splendid system of transcontinental railroads would make internal distribution not a particularly difficult matter. Above all such considerations, of course, is the fact that the United States is an industrial and agricultural entity, self-supporting and self-feeding, and, therefore, it could not be starved into surrender even though the enemy should surmount these practically insuperable obstacles to a submarine blockade. But the situation of the British Isles is entirely different. They obtain from overseas the larger part of their food and a considerable part of their raw materials, and in April of 1917, according to reliable statements made at that time, England had enough food on hand for only six weeks or two months. The trade routes over which these supplies came made the submarine blockade a comparatively simple matter. Instead of the sticks of a fan, the comparison which I have suggested with our own coast, we now have to deal with the neck of a bottle. The trade routes to our Atlantic coast spread out, as they approach our ports; on the other hand, the trade routes to Great Britain converge almost to a point. The far-flung steamship lanes which bring Britain her food and raw materials from half a dozen continents focus in the Irish Sea and the English Channel. To cut the communications of Great Britain, therefore, the submarines do not have to patrol two or three thousand miles of sea-coast, as would be necessary in the case of the United States; they merely need to hover around the extremely restricted waters west and south of Ireland.
This was precisely the area which the Germans had selected for their main field of activity. It was here that their so-called U-boats were operating with the most deadly effect; these waters constituted their happy hunting grounds, for here came the great cargo ships, with food and supplies from America, which were bound for Liverpool and the great Channel ports. The submarines that did destruction in this region were the type that have gained universal fame as the U-boats. There were other types, which I shall describe, but the U-boats were the main reliance of the German navy; they were fairly large vessels, of about 800 tons, and carried from eight to twelve torpedoes and enough fuel and supplies to keep the sea for three or four weeks. And here let me correct one universal misapprehension. These U-boats did not have bases off the Irish and Spanish coasts, as most people still believe. Such bases would have been of no particular use to them. The cruising period of a submarine did not depend, as is the prevailing impression, upon its supply of fuel oil and food, for almost any under-water boat was able to carry enough of these essential materials for a practically indefinite period; the average U-boat, moreover, could easily make the voyage across the Atlantic and back. The cruising period depended upon its supply of torpedoes. A submarine returned to its base only after it had exhausted its supply of these destructive missiles; if it should shoot them all in twenty-four hours, then a single day would end that particular cruise; if the torpedoes lasted a month, then the submarine stayed out for that length of time. For these reasons bases on the Irish coast would have been useful only in case they could replenish the torpedoes, and this was obviously an impossibility. No, there was not the slightest mystery concerning the bases of the U-boats. When the Germans captured the city of Bruges in Belgium they transformed it into a headquarters for submarines; here many of the U-boats were assembled, and here facilities were provided for docking, repairing, and supplying them. Bruges was thus one of the main headquarters for the destructive campaign which was waged against British commerce. Bruges itself is an inland town, but from it two canals extend, one to Ostend and the other to Zeebrugge, and in this way the interior submarine base formed the apex of a triangle. It was by way of these canals that the U-boats reached the open sea.
Once in the English Channel, the submarines had their choice of two routes to the hunting grounds off the west and south of Ireland. A large number made the apparently unnecessarily long detour across the North Sea and around Scotland, going through the Fair Island Passage, between the Orkney and the Shetland islands, along the Hebrides, where they sometimes made a landfall, and so around the west coast of Ireland. This looks like a long and difficult trip, yet the time was not entirely wasted, for the U-boats, as the map of sinkings shows, usually destroyed several vessels on the way to their favourite hunting grounds. But there was another and shorter route to this area available to the U-boats. And here I must correct another widely prevailing misapprehension. While the war was going on many accounts were published in the newspapers describing the barrage across the English Channel, from Dover to Calais, and the belief was general that this barrier kept the U-boats from passing through. Unfortunately this was not the case. The surface boats did succeed in transporting almost at will troops and supplies across this narrow passage-way; but the mines, nets, and other obstructions that were intended to prevent the passage of submarines were not particularly effective. The British navy knew little about mines in 1914; British naval men had always rather despised them as the "weapons of the weaker power," and it is therefore not surprising that the so-called mine barrage at the Channel crossing was not successful. A large part of it was carried away by the strong tide and storms, and the mines were so defective that oysters and other sea growths, which attached themselves to their prongs, made many of them harmless. In 1918, Admiral Sir Roger Keyes reconstructed this barrage with a new type of mine and transformed it into a really effective barrier; but in the spring of 1917, the German U-boats had little difficulty in slipping through, particularly in the night time. And from this point the distance to the trade routes south and west of Ireland was relatively a short one.
Yet, terribly destructive as these U-boats were, the number which were operating simultaneously in this and in other fields was never very large. The extent to which the waters were infested with German submarines was another particularly ludicrous and particularly prevalent misapprehension. Merchant vessels constantly reported that they had been assailed by "submarines in shoals," and most civilians still believe that they sailed together in flotillas, like schools of fish. There is hardly an American doughboy who did not see at least a dozen submarines on his way across the Atlantic; every streak of suds which was caused by a "tide rip," and every swimming porpoise, was immediately mistaken for the wake of a torpedo; and every bit of driftwood, in the fervid imagination of trans-Atlantic voyagers, immediately assumed the shape of a periscope. Yet it is a fact that we knew almost every time a German submarine slunk from its base into the ocean. The Allied secret service was immeasurably superior to that of the Germans, and in saying this I pay particular tribute to the British Naval Intelligence Department. We always knew how many submarines the Germans had and we could usually tell pretty definitely their locations at a particular time; we also had accurate information about building operations in Germany; thus we could estimate how many they were building and where they were building them, and we could also describe their essential characteristics, and the stage of progress they which had reached at almost any day.
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 manœuvre 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 the problem which confronted us. Germany could do this, of course, because the restricted field in which she was able to operate was so constantly and so densely infested with valuable shipping.
In the above I have been describing the operations of the U-boats in the great area to the west and south of Ireland. But there were other hunting fields, particularly that which lay on the east coast of England, in the area extending from Harwich to Newcastle. This part of the North Sea was constantly filled with ships passing between the North Sea ports of England and Norway and Sweden, carrying essential products like lumber and many manufactured articles. Every four days a convoy of from forty to sixty ships left some port in this region for Scandinavia; I use the word "convoy," but the operation was a convoy only in the sense that the ships sailed in groups, for the navy was not able to provide them with an adequate escort—seldom furnishing them more than one or two destroyers, or a few yachts or trawlers. Smaller types of submarines which were known as UB's and UC's and which issued from Wilhelmshaven and the Skager Rack constantly preyed upon this coastal shipping. These submarines differed from the U-boats in that they were smaller, displacing about 350 and 400 tons, and in that they also carried mines, which they were constantly laying. They were much handier than the larger types; they could rush out much more quickly from their bases and get back, and they did an immense amount of damage to this coastal trade. The value of the shipping sunk in these waters was unimportant when compared with the losses which Great Britain was suffering on the great trans-Atlantic routes, but the problem was still a serious one, because the supplies which these ships brought from the Scandinavian countries were essential to the military operations in France.
Besides these two types, the U-boats and the UB's and UC's, the Germans had another type of submarine, the great ocean cruisers. These ships were as long as a small surface cruiser and were half again as long as a destroyer, and their displacement sometimes reached 3,000 tons. They carried crews of seventy men, could cross the Atlantic three or four times without putting into port, and some actually remained away from their bases for three or four months. But they were vessels very difficult to manage; it took them a relatively long time to submerge, and, for this reason, they could not operate around the Channel and other places where the anti-submarine craft were most numerous. In fact, these vessels, of which the Germans had in commission perhaps half a dozen when the armistice was signed, accomplished little in the war. The purpose for which they were built was chiefly a strategic one. One or two were usually stationed off the Azores, not in any expectation that they would destroy much shipping—the fact is that they sank very few merchantmen—but in the hope that they might divert anti-submarine craft from the main theatre of operations. In this purpose, however, they were not successful; in fact, I cannot see that these great cruisers accomplished anything that justified the expense and the trouble which were involved in building them.