Germany was suffering under a crushing British naval blockade, leading to widespread famine and the infamous ‘Turnip Winter.’ In a bid to break the deadlock, the Kaiser authorized unrestricted submarine warfare. Knowing this would likely provoke the United States, German Foreign Secretary Arthur Zimmermann devised a plan to keep American forces occupied at home by inciting a conflict between the U.S. and Mexico.

Zimmermann’s proposal was as bold as it was detached from reality. He offered Mexico:

• A formal military alliance with Germany.
• Financial support for the war effort.
• The promise of reclaiming lost territories, specifically Texas, Arizona, and New Mexico.

However, Zimmermann failed to account for Mexico’s internal instability and its inability to challenge a major military power.

The British had established ‘Room 40,’ a secret intelligence unit composed of linguists and mathematicians who intercepted German communications. When they decrypted the Zimmermann Telegram, they faced a dilemma: how to reveal the plot to the U.S. without admitting they were spying on American diplomatic cables. This mirrors the complex intelligence games seen in other historical mysteries, such as The Antikythera Mechanism.

To protect their intelligence sources, British agents ‘laundered’ the information by obtaining a copy of the telegram from a commercial telegraph office in Mexico City. By presenting this version to the American Ambassador, they successfully framed the intelligence as a discovery made on neutral ground, effectively removing the diplomatic stain of eavesdropping on their allies.