What was the main result of Germany’s use of unrestricted submarine warfare during World War I?

Germany’s unrestricted submarine warfare meant its submarines could attack ships without warning, including ships connected to neutral countries. Attacks on vessels such as the Lusitania, and Germany’s renewed submarine campaign in 1917, helped turn American public opinion against Germany and led the United States to enter the war on the Allied side. The main result was therefore not fewer countries joining the war, but U.S. involvement.

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