What was one effect of unrestricted German submarine attacks on shipping in world war i?

One significant effect of unrestricted German submarine attacks on shipping during World War I was the escalation of tensions between Germany and neutral countries, particularly the United States. These attacks led to the sinking of civilian and merchant ships, including the Lusitania in 1915, resulting in loss of American lives and increasing public outrage. Consequently, the U.S. was drawn closer to entering the war on the side of the Allies, significantly impacting the conflict's outcome.