Which event is often referred to as the catalyst for U.S. involvement in World War I?

The sinking of the Lusitania is often regarded as a significant catalyst for U.S. involvement in World War I due to its impact on public opinion and foreign policy. The Lusitania was a British ocean liner that was torpedoed by a German U-boat in May 1915, resulting in the loss of over 1,100 lives, including 128 Americans. This event shocked the American public and led to increased anti-German sentiments. While the United States had not yet committed to entering the war following this incident, it heightened calls for action against Germany and drew greater attention to the danger posed by unrestricted submarine warfare.

Furthermore, the sinking of the Lusitania was instrumental in shaping the narrative surrounding Germany's actions during the war, as it raised questions about Germany's willingness to target civilian vessels. This incident, coupled with other factors, such as economic interests and diplomatic communications like the Zimmermann Telegram, ultimately pushed the United States closer to intervention in 1917, marking a critical turning point in the war. Therefore, it is the key event that catalyzed U.S. engagement in World War I.