Zimmermann Telegram
The Zimmermann Telegram was a telegram to Mexico from Germany. It told Mexico of Germany's plan to bomb some ships with their U-Boats. In the telegram, Germany was asking whether, if America joins from the attack, Mexico would join the war as an ally to Germany. But the telegram was intercepted in England and eventually, it was decoded. After being decoded, it was shown to the U.S. The Americans were very angry, and had many anti-German feelings growing.