What was the zimmerman telegram?

It's was a telegram send by the Germans to Mexico to the war allies and keep the U. S. Out of the war Europe because they were fighting Mexico but the plain backfire and U. S. Ended up joining the war

The Zimmermann Telegram was a coded message sent from German Foreign Minister Arthur Zimmermann to Germany's ambassador in Mexico, Heinrich von Eckhardt, in January 1917. The British managed to intercept this coded message and were able to decipher it.

Within this secret message, Zimmermann revealed Germany's plan to restart unrestricted submarine warfare as well as offered Mexico territory from the United States if Mexico were to declare war on the United States.