Such was the mystery ship idea in its simplest form. In the early days it worked according to this programme. The trustful submarine commander who approached a mystery ship in the manner which I have described promptly found his resting-place on the bottom of the sea. I have frequently wondered what must have been the emotions of this first submarine crew, when, standing on the deck of their boat, steaming confidently toward their victim, they saw its bulwarks suddenly drop, and beheld the ship, which to all outward appearances was a helpless, foundering hulk, become a mass of belching fire and smoke and shot. The picture of that first submarine, standing upright in the water, reeling like a drunken man, while the apparently innocent merchant ship kept pouring volley after volley into its sides, is one that will not quickly fade from the memory of British naval men. Yet it is evident that the Allies could not play a game like this indefinitely. They could do so just as long as the Germans insisted on delivering themselves into their hands. The complete success of the idea depended at first upon the fact that the very existence of mystery ships was unknown to the German navy. All that the Germans knew, in these early days, was that certain U-boats had sailed from Germany and had not returned. But it was inevitable that the time should come when a mystery ship attack would fail; the German submarine would return and report that this new terror of the seas was at large. And that is precisely what happened. A certain submarine received a battering which it seemed hardly likely that any U-boat could survive; yet, almost by a miracle, it crept back to its German base and reported the manner of its undoing. Clearly the mystery ships in future were not to have as plain sailing as in the past; the game, if it were to continue, would become more a battle of wits; henceforth every liner and merchantman, in German eyes, was a possible enemy in disguise, and it was to be expected that the U-boat commanders would resort to every means of protecting their craft against them. That the Germans knew all about these vessels became apparent when one of their naval publications fell into our hands, giving complete descriptions and containing directions to U-boat commanders how to meet this new menace. The German newspapers and illustrated magazines also began to devote much space to this kind of anti-submarine fighting, denouncing it in true Germanic fashion as "barbarous" and contrary to the rules of civilized warfare. The great significance of this knowledge is at once apparent. The mere fact that a number of Q-ships were at sea, even if they did not succeed in sinking many submarines, forced the Germans to make a radical change in their submarine tactics. As they could no longer bring to, board, and loot merchant ships, and sink them inexpensively and without danger by the use of bombs, they were obliged not only to use their precious