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Why did Germany mention Mexico’s lost territory in the Zimmermann Telegram?

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How the Mexican-American War changed the U.S. forever — Mexican-American War Learn how the Mexican-American War ultimately pushed the United States closer to civil war.

In 1917, German Foreign Secretary Arthur Zimmermann sent a secret telegram proposing a military alliance with Mexico in the event that the United States entered World War I against Germany.12

Germany’s strategic goal was to nullify or reduce U.S. intervention in Europe by forcing the United States to commit its military resources and energies to a conflict closer to home. By offering German support for Mexico to reconquer its "lost territory"—specifically the lands ceded to the U.S. following the Mexican-American War and the Treaty of Guadalupe Hidalgo—Zimmermann aimed to embroil the United States in a war with Mexico and Japan.132

The telegram, which explicitly mentioned the recovery of Texas, New Mexico, and Arizona, was intercepted by British intelligence and publicized, ultimately serving as a major factor in the U.S. decision to declare war on Germany.12