What was the Zimmermann Telegram and how did it influence U.S. entry into World War I?

The Zimmermann Telegram was a secret coded message sent on January 16, 1917, by German Foreign Secretary Arthur Zimmermann to the German minister in Mexico.12

The telegram proposed a military alliance between Germany and Mexico should the United States enter World War I against Germany. As an incentive, Germany promised financial support and assistance for Mexico to reconquer its "lost territory" in Texas, New Mexico, and Arizona. The message also suggested that Mexico invite Japan to join the alliance.123

British intelligence intercepted and decoded the message, sharing it with the U.S. government. When President Woodrow Wilson authorized its publication on March 1, 1917, the revelation caused widespread public outrage. By demonstrating clear German hostility toward the United States, the telegram shattered American neutrality and became a decisive factor in the U.S. declaration of war against the German Empire just five weeks later.231