File:Ww1 zimmerman cartoon.jpeg

In January of 1917, British cryptographers deciphered a telegram from German Foreign Minister Arthur Zimmermann to the German Minister to Mexico, von Eckhardt, offering United States territory to Mexico in return for joining the German cause. This message helped draw the United States into the war and thus changed the course of history.

http://www.archives.gov/global-pages/larger-image.html?i=/education/lessons/zimmermann/images/decoded-message-l.jpg&c=/education/lessons/zimmermann/images/decoded-message.caption.html