What was one major reason for the U.S. involvement in World War I?

The sinking of the Lusitania was a pivotal event that significantly influenced U.S. involvement in World War I. In May 1915, a British ocean liner, the Lusitania, was torpedoed by a German U-boat, resulting in the deaths of 1,198 passengers, including 128 Americans. This incident sparked outrage among the American public and intensified anti-German sentiment in the United States. The loss of American lives on a civilian ship raised questions about Germany's unrestricted submarine warfare policy and was perceived as a direct threat to American citizens and maritime rights.

Additionally, the Lusitania was carrying munitions, which further justified the U.S. perspective that Germany was waging an aggressive and barbaric war. The British propaganda surrounding the event portrayed Germany as violating international norms and laws regarding warfare and the safety of civilians. Consequently, this event contributed to shifting public opinion and increasing political pressure on President Woodrow Wilson to take a stand against Germany, ultimately leading to the U.S. entering the conflict in April 1917.