The RMS Lusitania, a British ocean liner, was torpedoed and sunk by a German U-boat off the coast of Ireland, resulting in the deaths of 1,198 passengers and crew, including 128 Americans. Germany justified the attack by claiming the ship was carrying secret war munitions (which was later proven true). However, the deaths of so many civilians caused an international outcry and shifted public opinion in the United States against Germany. While it took another two years for the U.S. to officially enter the war, the sinking ended the 'unrestricted submarine warfare' policy for a time and hardened American resolve. It remains one of the most controversial maritime disasters in history, highlighting the clash between traditional 'rules of war' and the new, lethal technology of the submarine.