Annotation: In January 1917, Germany announced that it would resume unrestricted submarine warfare. This announcement helped precipitate American entry into the conflict. Germany hoped to win the war within five months, and they were willing to risk antagonizing Wilson on the assumption that even if the United States declared war, it could not mobilize quickly enough to change the course of the conflict.
Then a fresh insult led Wilson to demand a declaration of war. In March 1917, newspapers published the Zimmerman Note, an intercepted telegram from the German Foreign Secretary Arthur Zimmerman to the German ambassador to Mexico. The telegram said that if Germany went to war with the United States, Germany promised to help Mexico recover the territory it had lost during the 1840s, including Texas, New Mexico, California, and Arizona. The Zimmerman Note and German attacks on three U.S. ships in mid-March led Wilson to ask Congress for a declaration of war.
Wilson decided to enter the war so that he could help design the peace settlement. Wilson viewed the war as an opportunity to destroy German militarism. "The world must be made safe for democracy," he told a joint session of Congress. Only 6 Senators and 50 Representatives voted against the war declaration.
Document: The Zimmerman Note to the German Minister to Mexico
Berlin, January 19, 1917
On the first of February we intend to begin submarine warfare unrestricted. In spite of this, it is our intention to endeavor to keep neutral the United States of America.
If this attempt is not successful, we propose an alliance on the following basis with Mexico: That we shall make war together and together make peace. We shall give general financial support, and it is understood that Mexico is to reconquer the lost territory in New Mexico, Texas, and Arizona. The details are left to you for settlement....
You are instructed to inform the President of Mexico of the above in the greatest confidence as soon as it is certain that there will be an outbreak of war with the United States and suggest that the President of Mexico, on his own initiative, should communicate with Japan suggesting adherence at once to this plan; at the same time, offer to mediate between Germany and Japan.
Please call to the attention of the President of Mexico that the employment of ruthless submarine warfare now promises to compel England to make peace in a few months.
Zimmerman (Secretary of State)