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 J-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
