19. The United States supported Great Britain while remaining officially neutral in 1915
The United States declared itself neutral in 1914, and remained so until it entered the war in 1917. Neutrality meant, under international law, the United States could continue to trade with all the belligerent nations. It was a violation of the rules of war to carry munitions on a neutral ship. Great Britain established a naval blockade of German ports which restricted trade. It was in response to the British blockade that the Germans declared a war zone in the waters surrounding Great Britain in 1915. The war zone applied to ships of neutral countries. Lusitania, though steaming unflagged, was easily recognizable as a British liner, it was one of the most famous and recognizable ships in the world.
The Germans, through their intelligence network in the United States and Great Britain, knew that Lusitania was carrying munitions, and that it had done so on previous voyages during the war. At the time of Lusitania’s sinking, no British ship had yet been hit by a torpedo when steaming at a speed exceeding 15 knots. Lusitania’s ability to exceed that speed throughout a voyage made the ship ideal for carrying cargo critical to Britain’s war effort. British purchasing of war material from the United States was perfectly legal, as was shipping it in the hull of a ship which was registered to the Royal Navy. It was a British decision not to inform the passengers of the nature of the cargo.