4. The Zimmermann Telegram (1917)
In January 1917, German Foreign Secretary Arthur Zimmermann sent a secret, coded message to the German ambassador in Mexico, proposing a military alliance against the United States. The telegram promised Mexico financial support and assistance in reclaiming territories lost during the Mexican-American War, including Texas, New Mexico, and Arizona. British intelligence intercepted and decrypted the message, revealing Germany’s intentions to incite conflict between the U.S. and Mexico. The British government presented the telegram to U.S. Ambassador Walter Hines Page on February 24, 1917. The revelation of the telegram’s contents caused outrage among the American public and significantly shifted public opinion toward supporting entry into World War I. On April 6, 1917, the United States Congress declared war on Germany, marking a pivotal moment in the nation’s history (archives.gov).
