In January of 1917, the British intercepted and decoded a secret telegram sent from German Foreign Secretary Arthur Zimmerman to the German ambassador in Mexico. He proposed that Mexico ally with Germany against the United States. He promised them the territories of Texas, New Mexico, and Arizona.
President Woodrow Wilson gave a speech to Congress on April 2, 1917 asking for them to declare war on Germany. In his speech he said that the U.S. would go to war to "fight for the ultimate peace of the world." On April 6, 1917 the U.S. officially declared war on Germany.
