The Zimmerman Note, or Zimmerman Telegram, was a coded message sent by the Germans to Mexico on January 16, 1917, which offered Mexico U.S. territory if it helped Germany in the First World War. The telegram was intercepted by British officials, who then shared the deciphered message with President Woodrow Wilson on February 24, 1917.
President Wilson, who had maintained a strict position of neutrality in the European conflict that had been waging, was swayed by finding out Germany's persuasions to draw the U.S. into a war with Mexico. Up to that point, tensions between the U.S. and Germany were rising, regardless, as American merchant ships were being attacked by German submarines.
In the telegram, Germany offered to assist Mexico in reclaiming Texas and much of the southwest U.S. area. Mexico, which was a far weaker country than the U.S., ignored the telegram and later officially rejected it once the U.S. declared war on Germany on April 6, 1917.
The Zimmerman telegram is now considered one of the most significant decoded messages in history. When the American newspapers first wrote about the telegram on March 1 of the same year, the news sparked a flurry of American outrage. Public opinion quickly shifted to favoring war against Germany and its allies.