1. Lusitania Sinking: The sinking of the British passenger ship Lusitania by a German U-boat in May 1915 was a turning point. Over 1,100 people, including American citizens, lost their lives. This event intensified public outrage in the United States and raised concerns about the safety of American travelers.
2. Zimmermann Telegram: In early 1917, the British intercepted and decoded a telegram sent by German Foreign Minister Arthur Zimmermann to the German ambassador in Mexico. The telegram proposed an alliance between Germany and Mexico, promising support for Mexico's efforts to regain territories lost to the United States in the Mexican-American War. The revelation of this plot further inflamed public sentiment against Germany.
3. Unrestricted Submarine Warfare: Germany's decision to resume unrestricted submarine warfare in February 1917, despite previous pledges to the United States, was a major factor in shaping Wilson's opinion. This policy threatened American ships and citizens traveling on the Atlantic and violated international law.
4. Influence of Domestic Sentiment: Wilson faced immense pressure from various groups within the United States, including the influential Preparedness Movement and the American Defense Society, which advocated for increased military preparedness. He also received support from prominent individuals like former President Theodore Roosevelt, who argued for intervention in the war.
5. Moral Obligations: Wilson believed that the United States had a moral obligation to support the Allies (Britain, France, and Russia) in their struggle against German militarism and autocracy. He saw the conflict as a fight for democracy, freedom, and the rights of small nations.
6. Public Opinion: Public opinion in the United States shifted in favor of intervention as the war progressed. Reports of German atrocities, including the sinking of hospital ships and the mistreatment of Belgian civilians, contributed to growing anti-German sentiment.
7. Call for Peace: Wilson also saw an opportunity to negotiate a peace that could prevent future conflicts. He believed that the United States could play a leading role in establishing a lasting peace and promoting democratic principles in the post-war world.
These factors combined to change Woodrow Wilson's opinion about entering World War I, leading to his decision to request a declaration of war from Congress in April 1917.