The Zimmermann note, or Zimmermann telegram, was a German proposal for Mexico to declare war on the United States if the United States declared war on Germany during World War I. The telegram helped generate support among the American populace for U.S. entry into the war.
German foreign secretary Arthur Zimmermann sent the telegram to Heinrich von Eckardt, the German ambassador to Mexico, on Jan. 16, 1917. In the telegram, Germany promised that Mexico would receive the territories of Texas, New Mexico and Arizona if Mexico declared war on the U.S. After British intelligence intercepted and decrypted the telegram, Walter H. Page, the U.S. ambassador to Britain, took the document to Woodrow Wilson, the U.S. president, on Feb. 24. On March 1, newspapers began to publish accounts of the telegram, which some initially dismissed as inauthentic. However, Zimmermann himself confirmed the document's authenticity, creating a wave of anti-German sentiment among the U.S. public. Combined with the anger over German attacks on American ships, this sentiment gave Wilson and the U.S. Congress the support they needed to declare war on Germany on April 6, 1917. The Mexican government officially rejected the German proposal after the U.S. chose to enter the war.