Interception of the Zimmermann Telegram: The interception and decoding of the Zimmermann Telegram, a secret diplomatic communication between Germany and Mexico proposing an alliance against the United States, further solidified American resolve to enter the war.
Attacks on American Shipping: The sinking of several American merchant ships by German U-boats, including the SS Housatonic and SS City of Memphis, heightened tensions between the United States and Germany.
Lusitania Sinking: The sinking of the British passenger ship Lusitania in May 1915, with over 100 American passengers among the casualties, sparked public outrage in the United States.
Propaganda and Propaganda Campaigns: Propaganda and media campaigns influenced American public opinion. Both the Allied Powers and Germany engaged in propaganda campaigns, shaping the perception of the war and influencing public sentiment.
Sabotage and Espionage: Incidents of sabotage and espionage by German agents in the United States further exacerbated tensions and contributed to the sense of betrayal and mistrust.