Sinking of the Lusitania: The sinking of the British passenger liner Lusitania by a German U-boat in May 1915 was a pivotal event that turned public sentiment in the United States against Germany. Over 100 Americans were among the 1,198 people who lost their lives in the attack. The incident sparked outrage in the U.S. and fueled strong anti-German sentiments.
Unrestricted Submarine Warfare: Germany's decision to resume unrestricted submarine warfare in early 1917 further exacerbated tensions with the United States. This policy involved targeting merchant ships without warning, even those carrying passengers. The sinking of unarmed merchant vessels and passenger ships led to a growing demand for action against Germany.
Zimmermann Telegram: The interception and revelation of the Zimmermann Telegram in early 1917 added fuel to the anti-German sentiment. The telegram was a secret message from German Foreign Secretary Arthur Zimmermann to the German ambassador in Mexico, proposing an alliance between Germany and Mexico against the United States. This revelation was seen as an act of betrayal and fueled public outrage.
Violation of Belgian neutrality: Germany's invasion of Belgium, which was a neutral country, in August 1914 also played a role in shaping U.S. public opinion. Many Americans sympathized with Belgium and were critical of Germany's aggressive actions.
Propaganda: The British and French governments, as well as influential figures in the United States, engaged in propaganda campaigns that portrayed Germany in a negative light and highlighted the atrocities committed by German troops during the war. This propaganda contributed to the growing negative perception of Germany among the American public.
These factors cumulatively led to a significant shift in U.S. public opinion against Germany, eventually leading to the country's entry into World War I on the side of the Allies in April 1917.