In January of 1917, British cryptographers deciphered a telegram from
German Foreign Minister Arthur Zimmermann to the German Minister to
Mexico, von Eckhardt, offering United States territory to Mexico in
return for joining the German cause. This message helped draw the
United States into the war and thus changed the course of history. The
telegram had such an impact on American opinion that, according to
David Kahn, author of The Codebreakers, "No other single cryptanalysis
has had such enormous consequences." It is his opinion that "never
before or since has so much turned upon the solution of a secret
message." In an effort to protect their intelligence from detection
and to capitalize on growing anti-German sentiment in the United
States, the British waited until February 24 to present the telegram
to Woodrow Wilson. The American press published news of the telegram
on March 1. On April 6, 1917, the United States Congress formally
declared war on Germany and its allies.