Zimmermann Telegram

In World War I, ciphered telegram sent by Alfred Zimmermann, German foreign secretary, discussing alliance against the USA with Mexico. The message was deciphered by British Naval Intelligence and its publication in the USA March 1917 caused uproar, playing a considerable part in the US decision to enter the war the following month.

Zimmermann sent the telegram to von Eckhardt, German ambassador to Mexico. In it he proposed that Eckhardt discuss with Mexico the recovery of their ‘lost’ territories of Texas, New Mexico, and Arizona in the event of US‐German hostilities. He also made remarks on unrestricted submarine warfare against the USA and the possibility of inveigling Japan into an alliance with Mexico. The message was intercepted and deciphered by the British naval intelligence service of Room 40, and a copy was passed to the US Ambassador, who in turn sent it to the US State Department. President Wilson permitted it to be published 1 March 1917 and its contents caused a public outcry. Zimmermann ‘resigned’ shortly afterward.