Answer:
The Zimmerman Telegram was essentially a diplomatic report issued from the German Foreign Office in 1917 that stated Germany's intentions to ally with Mexico in World War I. This greatly changed the course of the war for the United States because prior to its release, the United States took a very isolationist approach and was not going to intervene in the war. However, this prospective alliance led the United States to 'forego' its previous isolationist attitudes and intervene in the war.
Explanation:
I took AP US History during my junior year of high school and this was a big concept we covered. :)
