Picture of the Zimmerman Telegram

Photostat of the Zimmerman Telegram as received by the German ambassador to Mexico (Jan. 19, 1917)

In the midst of World War I, German Foreign Minister Arthur Zimmerman sent an encoded message to the President of Mexico proposing a military alliance against the United States. In return for Mexican support in the war, Germany would help Mexico regain New Mexico, Texas, and Arizona from the United States. The British intercepted the secret message, deciphered it, and turned it over to the U.S. Government.

Photograph from the National Archives and Records Administration.