Popular sentiment (feeling) in the United States at that time was anti-Mexican as well as anti-German. General John J. Pershing had long been chasing the revolutionary Pancho Villa , who had carried out several cross-border raids. News of the Telegram further inflamed tensions between the U.S. and Mexico.
At first, the Telegram was widely believed to be a forgery (fake) by British intelligence. However, first on March 3 , 1917 and later on March 29 , 1917 , Arthur Zimmermann himself admitted that the Telegram was genuine.
Woodrow Wilson responded by asking Congress to arm American ships so that they could fend (protect from) off potential German submarine attacks. A few days later, on April 2 , 1917 , Wilson asked Congress to declare war on Germany. On April 6 , 1917 , Congress complied (agreed), bringing the United States into World War I.