1. Neutrality was becoming increasingly difficult: The United States had declared neutrality at the start of the war, but it became increasingly difficult to maintain as the war intensified. American ships and citizens were being attacked by both sides, and the country's economic ties to both the Allied Powers and the Central Powers were strained.
2. German U-boat attacks: The German U-boat (submarine) campaign was a major factor in Wilson's decision to enter the war. In early 1917, Germany announced a policy of unrestricted submarine warfare, which meant that it would sink any ship, whether military or civilian, in the waters around Britain and France. This posed a direct threat to American commercial interests and the safety of American citizens traveling on passenger ships.
3. British propaganda: The British government engaged in a massive propaganda campaign to convince the American public that the war was a fight for freedom and democracy against the forces of tyranny and autocracy. This campaign, which included speeches, advertisements, and news articles, was very successful in shaping public opinion in the United States.
4. Lusitania: In May 1915, a German U-boat sank the British passenger ship Lusitania, killing over 1,000 people, including 128 Americans. This incident galvanized public opinion in the United States against Germany and increased calls for war.
5. Zimmerman Telegram: In January 1917, the British intercepted and decoded a telegram from German Foreign Minister Arthur Zimmermann to the German ambassador in Mexico. The telegram proposed an alliance between Germany and Mexico in which Mexico would attack the United States in return for German support in reconquering its lost territories in the Southwest. This telegram convinced many Americans that Germany was a threat to the security of the United States.