In 1914, the Germans were in possession of 30 submarines, the famous U-boats. These were not the ocean-going craft familiar to students of World War 2, but smaller craft designed to operate in coastal waters. They were, however, armed with numbers of self-propelled torpedoes, and were deadly enough. Of the 360 submarines Germany built during the Great War, half were captured or sunk, but they did succeed in destroying more than 12 million tons of shipping.
In May 1915, U-20, captained by one Walther Schwieger, torpedoed the passenger liner RMS Lusitania, killing over a thousand people, including some pretty irritated Americans.
But when Titanic went down didn't she take over 1,500 people with her? Yes, indeed, but what made the Lusitania sinking worse was the fact that the Titanic disaster was an accident, the Lusitania was sunk on purpose.
They say that he who lives by the sword dies by the sword, so it's perhaps no surprise that Captain Schwieger's own remains are still aboard his last command, U-88 - at the bottom of the North Sea. His submarine was sunk by the British Q-ship HMS Glenfoyle alias Stonecrop alias Dunlevon alias Winona.
A Q-ship was a fake merchantman equipped with hidden guns. These decoys were used by the Royal Navy to literally lure U-boats to their doom, hence the confusing array of names.