The practice of attacking any vessel, including civilian and neutral ships, without warning is known as unrestricted submarine warfare. This approach disregards the established rules of naval engagement, which traditionally required submarines to surface and allow passengers and crew to evacuate before sinking a ship. Such tactics became a significant point of contention during the First World War.
The adoption of this strategy by Germany had profound consequences for the United States. The sinking of ships carrying American citizens, most notably the Lusitania in 1915, fueled public outrage and increased pressure on the U.S. government to abandon its neutrality. This policy, therefore, directly contributed to the eventual entry of the United States into the conflict, shifting the balance of power in favor of the Allied forces. Its legacy continues to be studied in relation to international law and the conduct of war.
