During WWI, as part of the effort to beat back the German U-boat menace, the British Royal Navy made use of special decoy vessels known as Q-ships, which were heavily armed merchant ships carrying concealed weapons. Intended as bait to lure enemy submarines, the seemingly unarmed Q-ships would unveil their guns and sink the U-boats once they emerged to make a surface attack.
During the war’s first years, before Germany declared unrestricted submarine warfare in 1917 and began sinking ships at sight and without warning, the standard operating procedure was for U-boats to hail a civilian vessels, allowing their crews an opportunity to take to their lifeboats, before opening fire and sinking the ship with a torpedo, or more often, with shells from the U-boat’s deck gun when practicable, in order to save the more expensive torpedoes for tougher targets.
The Q-ship decoys were usually trawlers or freighters carrying hidden guns in collapsible deck structures. They would sail routes known to be heavily infested with U-boats, in the hopes of attracting the attention of a German submarine and enticing it to make an attack. When hailed by the U-boat, a portion of the crew, known as the “panic party”, would act like normal merchant sailors, terrified by the sudden appearance of an enemy submarine, and rush to the lifeboats to abandon ship.
Since the use of expensive and powerful torpedoes to sink relatively easy targets such as trawlers and freighters would be overkill, and was also officially frowned upon, the U-boat’s captain would normally close the distance to the now “abandoned” ship, in order to open fire from close range and sink it with the deck gun. Once the submarine got close enough, hidden crewmen remaining on board the Q-board would haul down the merchant flag and raise the Royal Navy’s ensign, while other crew would collapse the deck structure, revealing up to four guns manned and ready for action, which would open fire and sink the surprised U-boat.
The decoy vessels were quite successful when first introduced, and within months, Q-ships claimed 11 German submarines. However, as the war progressed, German submariners learned to be wary, and to approach small vessels with a healthy dose of caution, lest they turn out to be Q-ships carrying concealed weapons. At the slightest suspicion, torpedoes were used as a first option to sink vessels from a safe distance. After the Germans turned to open submarine warfare in 1917 and began sinking ships without warning, the utility of the Q-ships came to an end, as their effectiveness had depended on U-boats hailing and coming close enough for the decoy ship to surprise them, and once the Germans abandoned that standard operating procedure, Q-ships became useless.