Advanced Placement US History (AP US History) Practice Exam 2026 – The Comprehensive All-in-One Guide to Exam Success!

The U.S. entry into World War I was primarily catalyzed by the combination of the sinking of the Lusitania and the content of the Zimmerman Telegram.

The Lusitania, a British ocean liner, was sunk by a German U-boat in May 1915, resulting in the deaths of 128 Americans among other passengers. This event generated significant outrage in the United States, as Americans were shocked by the loss of civilian life. It brought the issue of unrestricted submarine warfare by Germany to the forefront of public consciousness and intensified anti-German sentiment in the country.

Furthermore, the Zimmerman Telegram played a critical role in escalating tensions. In early 1917, the British intercepted a secret communication from German Foreign Minister Arthur Zimmermann to Mexico, proposing a military alliance against the United States. This revelation further alarmed Americans and fueled calls for the U.S. to join the conflict, as it implied a direct threat to national security.

Together, these events significantly shifted public opinion and political sentiment in favor of entering the war, leading President Woodrow Wilson to ask Congress for a declaration of war against Germany in April 1917. The sinking of the Lusitania showcased the dangers of the German military strategy, while the Zimmerman Telegram represented a direct challenge