Zimmermann Telegram

The Zimmermann Telegram (or Zimmermann Note) was an internal diplomatic communication issued from the German Foreign Office in January, 1917 that proposed a military alliance between Germany and Mexico in the event of the United States' entering World War I against Germany. The proposal was intercepted and decoded by British intelligence. Revelation of the contents enraged American public opinion and helped generate support for the United States declaration of war on Germany in April of the same year.