Final answer:
The Zimmermann Telegram was a secret communication from Germany proposing a military alliance with Mexico to regain lost territory in the US.
Step-by-step explanation:
The Zimmermann Telegram was a secret communication sent by Arthur Zimmermann, the German Foreign Secretary, to the German ambassador in Mexico during World War I. The telegram proposed a military alliance between Germany and Mexico, with the intention of Mexico recovering lost territory in Texas, New Mexico, and Arizona, if the United States entered the war against Germany. This information was intercepted and decoded by the British, who then shared it with the United States. The Zimmermann Telegram was a significant factor that led to the United States joining World War I on the side of the Allies.
Learn more about Zimmermann Telegram