The Zimmermann Telegram (or Zimmermann Note or Zimmerman Cable) was a secret diplomatic communication issued from the German Foreign Office in January 1917 that proposed a military alliance between Germany and Mexico.
Explanation:
On January 16, 1917, British code breakers intercepted an encrypted message from Zimmermann intended for Heinrich von Eckardt, the German ambassador to Mexico. The British cryptographic office known as “Room 40” decoded the Zimmermann Telegram and handed it over to the United States in late-February 1917.
It was a secret message sent by German foreign secretary Arthur Zimmerman to the German ambassador in Mexico, Heinrich von Eckardt, in early 1917. It instructed the diplomat to approach the Mexican government if the United States entered WWI on the allied side, propose a secret alliance and offer Mexico financial and military aid to attack the US and support to recover "lost territory" of Arizona, New Mexico and Texas. The message was intercepted and decoded by British intelligence, which gave it to the USA. It was published by American newspapers, causing public outrage and support to enter the war.
