The Zimmerman Telegram

The Zimmerman Telegram is the name given to a message sent from Germany to Mexico. The message offers Mexico an alliance should the United States of America enter the war on the side of the Allies as a consequence of the Germans adoption of unrestricted submarine warfare. The telegram was intercepted and decoded by British code-breakers and passed to the Americans in order to encourage them to join the Allied cause.

The telegram was sent from the German Foreign Office Secretary of State, Arthur Zimmermann, to the German ambassador in the Mexico, Heinrich von Eckardt.

The telegram instructed Eckardt to approach the Mexican Government with an offer to recover lost territories and financial support should the US look as if it was about to enter the war.

The telegram was intercepted as it was transmitted by transatlantic cable and passed to Room 40, the British admiralty’s codebreaking operation. German transatlantic cables had been cut at the outbreak of the war and, as a result, they were reliant on Swedish and American cables that relayed through a British relay station near Lands End in Cornwall.

The telegram was decrypted within a day of receipt and passed to the Foreign Office. A variety of cover stories, designed to preserve the relay station as a valuable source of intelligence, were constructed to explain how the telegram has ended up in British hands.

The Zimmerman Telegram with decryption notes
The Zimmerman Telegram with decryption notes

The full text of the telegram is as follows…

We intend to begin, on February 1st, unrestricted submarine warfare. We shall endeavour in spite of this to keep the United States of America neutral. In the event of this not succeeding, we make Mexico a proposal of alliance on the following basis: make war together, make peace together, generous financial support and an understanding on our part that Mexico is to reconquer the lost territory in Texas, New Mexico and Arizona. The settlement in detail is left to you. You will inform the President of the above most secretly as soon as the outbreak of war with the United States of America is certain, and add the suggestion that he should, on his own initiative, invite Japan to immediate adherence and at the same time mediate between Japan and ourselves. Please call the President’s attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace.


Zimmermann (Foreign minister)

The British showed the telegram to Edward Bell, at the United States Embassy in Britain on the 19th of February. He was concerned that it was a fake, however was soon convinced of its veracity (the British showed certain intercept information that could be checked against telegraphic records) and passed it to Walter Hines Page, the US Ambassador to Britain. The Ambassador duly passed the information to President Woodrow Wilson who, in turn, released it to the Press on the 28th February 1917.

A lively debate ensued over whether the telegram was a fake but by March Zimmerman himself had admitted it was true to both the press and the Reichstag. The telegram, with its offer of an alliance with the Mexicans, who were already a thorn in the side of the US authorities, coupled with the onset of unrestricted submarine warfare on the 1st of February, shifted the needle towards eventual American involvement in the war.

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