After Germany's U-boats sank the Lusitania in 1915, Germany promised to limit submarine warfare. This promise was made in response to international outrage over the sinking of the British ocean liner, which resulted in the loss of many civilian lives, including Americans. By limiting submarine warfare, Germany aimed to avoid further provocation of neutral countries like the United States, which could potentially enter World War I against Germany.
By restricting the use of unrestricted submarine warfare, Germany hoped to prevent incidents like the sinking of the Lusitania from escalating and drawing more countries into the conflict. This promise marked a strategic shift in Germany's naval tactics during the war, reflecting an effort to manage international relations and avoid additional conflicts beyond the already existing war on the western front.