Question: What caused the United States enter World War I? (scroll down for answer)       Answer: Before the war, the United States remained neutral. However, certain international events changed this. It’s good to know...The Boat and The Note. 1. The Boat - The Lusitania. It was a passenger ship sailing off the coast of Ireland. It was sunk by a German submarine (u-boat) on May 7, 1915. The US warned Germany to refrain from continued submarine warfare. However, the Germans would not stop. 2. The Note - The Zimmermann Telegram. In 1917, the British intercepted a telegram from Arthur Zimmermann of Germany. He was writing to Mexico seeking an alliance. He hoped for a Mexican invasion of America where territory lost in the Mexican War would ultimately be reclaimed.  The Germans continued their policy of unrestricted submarine warfare. President Woodrow Wilson asked Congress to declare war in April of 1917. He was hoping to make the world “safe for democracy.” Click here for next flash card.      Back to eFlashcard headquarters