Final answer:
The primary message of the Zimmermann Telegram was a proposal for an alliance between Germany and Mexico against the United States.
Step-by-step explanation:
The primary message of the Zimmermann Telegram during World War I was that the German foreign minister proposed an alliance with Mexico against the U.S. The telegram, intercepted by Britain, revealed a secret plan in which Germany would provide military support to Mexico if it were to join the war against the United States. This message was an attempt by Germany to distract and divert American forces from Europe.
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