Primary sourceDocument1917

Zimmermann Telegram

Arthur Zimmermann · 1917

An intercepted 1917 German proposal for a military alliance with Mexico against the United States, which helped push Wilson toward declaring war.

This intercepted telegram, revealed to Wilson in 1917, pushed him and American public opinion toward declaring war on Germany.

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Scan of the encrypted Zimmermann Telegram on a Western Union telegram form, addressed to German Legation, Mexico City, via Galveston, dated January 1917. The body is a grid of groups of numbers, signed Bernstorff at the bottom, with a handwritten 'Charge German Embassy' note and a Western Union 'Night Letter' header. — Zimmermann Telegram, 1917. U.S. National Archives.

About this source

What it is

This is a coded telegram sent in January 1917 by German Foreign Secretary Arthur Zimmermann to the German minister in Mexico, proposing a military alliance against the United States if the U.S. entered World War I. It is held by the U.S. National Archives.

Why it matters

British codebreakers intercepted and decoded the telegram, which was released to President Wilson and published in American newspapers in March 1917. The threat of a German-Mexican alliance against the United States outraged public opinion and helped move Congress toward declaring war on Germany weeks later. The document shows how intelligence and secret diplomacy could shape a president's decisions and a nation's path to war.

Look closer

Why did the British wait before showing Wilson the telegram?
How might ordinary Americans have reacted to learning of this proposal?
What does this episode reveal about the role of secret communications in diplomacy and war?

This document is part of the curated material that grounds the AI version of Woodrow Wilson on Humy.ai — when students ask about related events, the AI can quote it and cite it.