Many merchantmen, both Allied and neutral, owed their escape to this camouflage warfare, which was brought to a high pitch of perfection and daring in the now famous mystery ships.
What may be said to form the second method of anti-submarine warfare was the decoy or camouflage system. Of primary importance in this category were the mystery ships already described, but there were also innumerable other ruses de guerre which increased its efficiency.
To describe one of these will enable the reader to draw on his own imagination for the remainder. A vessel was steaming in from the Atlantic and was about a hundred miles from the Cornish coast when she was attacked by a submarine above water. The surface ship was heavily armed, but instead of using her weapons at once she sent out frantic wireless signals for assistance. Every few minutes the call went far and wide in plain Morse.
The shells from the submarine splashed into the sea around, but none struck the target for some minutes. Had the surface ship desired, she could in all probability have avoided the under-water craft by using her superior speed, but instead she dropped back, allowing the submarine to catch up to her, and the shells began to burst unpleasantly close.
Still the frantic wireless calls went forth. First the simple message: "I am being attacked by a large German submarine." Then the vehemence increased to: "I am being heavily shelled." A few minutes elapsed and then the call: "Help. Submarine gaining on me." And finally: "Abandoning ship."
At this point the submarine was close astern and the liner slowing down preparatory to lowering her life-boats. The shells were damaging her superstructure, but a heavy swell interfered with the German marksmanship. Then came the surprise. A life-boat on the liner's poop was hoisted clear of the deck and from under its cover there appeared the lean grey muzzle of a 4.7-inch gun. A few sharp blasts of cordite and the submarine sagged and disappeared.
The captain of the liner had noticed when first attacked that the submarine was fitted with wireless and the calls sent out by him were in plain Morse code. On the strength of these the German commander had saved his torpedoes but lost his ship.
Another form of anti-submarine tactics was the employment of indicator and mined nets around an apparently disabled ship, or in lines across narrow channels known to be used by German submarines on their way to and from their bases. This method has, however, received full mention in other chapters.