Sinking of the RMS Lusitania

RMS Lusitania was a British-registered ocean liner that was torpedoed by an Imperial German Navy U-boat during the First World War on 7 May 1915, about 11 nautical miles (20 kilometres; 13 miles) off the Old Head of Kinsale, Ireland (then part of the United Kingdom). The attack took place in the declared maritime war-zone around the United Kingdom, three months after unrestricted submarine warfare against the ships of the United Kingdom had been announced by Germany following the Allied powers' implementation of a naval blockade against it and the other Central Powers.

Source: Wikipedia — Sinking of the RMS Lusitania (CC BY-SA 4.0)