Final answer:
The Zimmermann Telegram persuaded the US to enter World War I by proposing a military alliance between Germany and Mexico against the US. This secret message, intercepted and decoded by British intelligence, was a significant factor in the US formally declaring war on Germany.
Step-by-step explanation:
The significance of the Zimmermann Telegram to World War I was that it played a role in persuading the United States to enter the war. The Zimmermann Telegram was a secret message sent by Germany to Mexico in 1917, proposing a military alliance against the US if the US entered the war. The telegram was intercepted and decoded by British intelligence, who then shared it with the US. The revelation of this telegram outraged the American public and contributed to the US formally declaring war on Germany.
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