The sinking of the Cunard ocean liner RMS Lusitania occurred on Friday, 7 May 1915 during WW1, as Germany waged submarine warfare against the United Kingdom which had implemented a naval blockade of Germany.
When Lusitania was built, her construction and operating expenses were subsidized by the British government, with the provision that she could be converted to an Armed Merchant Cruiser if need be. At the outbreak of WW1, the British Admiralty considered her for requisition as an armed merchant cruiser, and she was put on the official list of AMCs.
The Admiralty then canceled their earlier decision and decided not to use her as an AMC after all; large liners such as Lusitania consumed enormous quantities of coal (910 tons/day, or 37.6 tons/hour) and became a serious drain on the Admiralty's fuel reserves, so express liners were deemed inappropriate for the role when smaller cruisers would do. They were also very distinctive; so smaller liners were used as transports instead. Lusitania remained on the official AMC list and was listed as an auxiliary cruiser in the 1914 edition of Jane's All the World's Fighting Ships, along with Mauretania.
The ship was identified and torpedoed by the German U-boat U-20 and sank in 18 minutes, and also took on a heavy starboard list. The vessel went down 11 miles (18 km) off the Old Head of Kinsale, Ireland, killing 1,198 and leaving 761 survivors. The sinking turned public opinion in many countries against Germany, contributed to the American entry into World War I and became an iconic symbol in military recruiting campaigns of why the war was being fought.
By early 1915, a new threat to British shipping began to materialise: U-boats (submarines). At first, the Germans used them only to attack naval vessels, and they achieved only occasional—but sometimes spectacular—successes. U-boats then began to attack merchant vessels at times, although almost always in accordance with the old cruiser rules. Desperate to gain an advantage on the Atlantic, the German government decided to step up its submarine campaign. On 4 February 1915, Germany declared the seas around the British Isles a war zone: from 18 February, Allied ships in the area would be sunk without warning. This was not wholly unrestricted submarine warfare, since efforts would be taken to avoid sinking neutral ships.
Lusitania fell victim to torpedo attack relatively early in the First World War, before tactics for evading submarines were properly implemented or understood. The contemporary investigations in both the United Kingdom and the United States into the precise causes of the ship's loss were obstructed by the needs of wartime secrecy and a propaganda campaign to ensure all blame fell upon Germany. Argument over whether the ship was a legitimate military target raged back and forth throughout the war as both sides made misleading claims about the ship. At the time she was sunk, she was carrying over 4 million rounds of small-arms ammunition (.303 caliber), almost 5,000 shrapnel shell casings (for a total of some 50 tons), and 3,240 brass percussion fuses, in addition to 1,266 passengers and a crew of 696. Several attempts have been made over the years since the sinking to dive to the wreck seeking information about precisely how the ship sank, and argument continues to the present day.
https://en.wikipedia.org/wiki/Sinking_of_the_RMS_Lusitania .
https://en.wikipedia.org/wiki/List_of_ships_sunk_by_submarines_by_death_toll .
