Days to Remember by John Buchan — Read

It was towards the end of 1914 that the German Admiralty conceived the idea of blockading the British Isles by means of a submarine fleet. The enterprise was a difficult one; for the pursuit and capture of commerce a submarine is very ill fitted. A frail boat with a small crew cannot afford to hold up and examine a ship on the surface; still less to put a prize crew on board and send the captured vessel into port. It was therefore decided that to carry out the blockade merchant ships must be sunk without examination and without warning. If crews, passengers, or even neutrals perished in this process, the "blame," says Admiral Scheer, "would attach to those who despised our warnings. " No civilized power had ever before threatened to kill non-combatants on logical principles of this kind, and as soon as it was seen that the German Admiralty were attempting to carry out their murderous intentions it became necessary to devise means of destroying their U-boats wherever they could be found.

They were accordingly hunted by destroyers, by trawlers, by submarines, and by airships and seaplanes; they were destroyed by gun fire, by mines, by nets, by torpedoes, and by depth charges, and all these were used with the greatest skill and success. Of all the hunting methods, perhaps the most attractive to the English sporting instinct was that of the Mystery Ships, or Q-boats. This was at first merely the use of a simple trap, but was developed by the genius of a single man into an entirely novel campaign of the most heroic kind.