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The Zimmermann Telegram as it was sent from Washington to Mexico
The Zimmermann Telegram (or Zimmermann Note; ; ) was a coded telegram dispatched by the Foreign Secretary of the German Empiremarker, Arthur Zimmermann, on January 16, 1917, to the Germanmarker ambassador in Washingtonmarker, Johann von Bernstorff, at the height of World War I. On January 19, Bernstorff, per Zimmermann's request, forwarded the Telegram to the German ambassador in Mexicomarker, Heinrich von Eckardt. Zimmermann sent the Telegram in anticipation of the resumption of unrestricted submarine warfare by the German Empire on February 1, an act which German chancellor Bethmann-Hollweg feared would draw the neutral United States into war on the side of the Allies. The Telegram instructed Ambassador Eckardt that if the United States appeared likely to enter the war he was to approach the Mexican government with a proposal for military alliance. He was to offer Mexico material aid in the reclamation of territory lost during the Mexican-American War, specifically the American states of Texasmarker, New Mexicomarker, and Arizonamarker. Eckardt was also instructed to urge Mexico to help broker an alliance between Germany and Japanmarker.

The Zimmermann Telegram was intercepted and decoded by the British cryptographers of Room 40. The revelation of its contents in the American press on March 1 caused public outrage that contributed to the United States' declaration of war against Germany and its allies on April 6.

The Telegram

Zimmermann's message was :
On the first of February, we intend to begin unrestricted submarine warfare. In spite of this, it is our intention to endeavor to keep the United States of America neutral.

In the event of this not succeeding, we propose an alliance on the following basis with Mexico: That we shall make war together and make peace together. We shall give generous financial support, and an understanding on our part that Mexico is to reconquer the lost territory in New Mexico, Texas, and Arizona. The details of settlement are left to you.

You are instructed to inform the President [of Mexico] of the above in the greatest confidence as soon as it is certain that there will be an outbreak of war with the United States and suggest that the President, on his own initiative, invite Japan to immediate adherence with this plan; at the same time, offer to mediate between Japan and ourselves.

Please call to the attention of the President that the ruthless employment of our submarines now offers the prospect of compelling England to make peace in a few months.

Mexican response

Mexican President Venustiano Carranza assigned a general to assess the feasibility of a Mexican takeover of their former territories . The general concluded that it would not be possible or even desirable for the following reasons:

  • Attempting to re-take the former territories would mean certain war with the United States.

  • No matter how "generous" it was, Germany's "financial support" would be worthless. Mexico could not use it to acquire arms, ammunition, or other war supplies, because the United States was the only sizable arms manufacturer in the Americas. The Royal Navy controlled the Atlantic sea lanes, so Germany could not possibly supply any quantity of arms.

  • Even if Mexico had the military means to re-take the territory it would have had severe difficulty accommodating and/or pacifying the large English-speaking population.

  • Mexico had even cooperated with the ABC nations to prevent a war with the United States, generally improving relations. If Mexico were to enter war against USA it would strain relations with ABC nations—who would later declare war on Germany.

Carranza formally declined Zimmermann's proposals on April 14, by which time the U.S. had declared war on Germany.

British interception

The Telegram was transmitted by radio and also across two telegraph routes under the cover of diplomatic messages by two neutral governments, Sweden and the United States. Germany lacked direct telegraphic access to the Western hemisphere because the British had cut the German cables in the Atlantic and shut down German stations in neutral countries. This forced Germany to use British and American cables instead despite the risk of interception. The Zimmermann messages passed over cables that touched on British soil, and as a result were intercepted there by British intelligence. President Woodrow Wilson had granted the German diplomats the privilege of sending their messages under the cover of U.S. diplomatic traffic in hopes that this would enable Germany to remain in touch with the United States and further Wilson's aims of ending the war. The message passing through this way was sent from Berlinmarker to the German ambassador in Washingtonmarker, Johann von Bernstorff, for re-transmission to von Eckardt in Mexico. What was a privilege provided to further peace actually brought war.

The Telegram was intercepted as soon as it was sent. The codebreakers in Room 40 at the Admiralty received a copyand decrypted enough to get the gist of it. The German Foreign Office encrypted the Telegram with cipher 0075, which Room 40 had partly broken.

The British government wanted to use the incriminating Telegram. It provided a splendid opportunity to draw the United States into World War I on the Allied side. Anti-German feeling in the United States was particularly strong at that moment, due to the German policy of "unrestricted" submarine warfare.

But the British had two problems. They had to explain to the Americans how they got the ciphertext of the Telegram, without telling the Americans about the British intelligence operation monitoring neutral diplomatic traffic, and they had to have a public explanation of how they had the Telegram's deciphered text without revealing to Germany that they had broken German cypher.

The British solved the first problem by also getting the ciphertext of the Telegram from the telegraph office in Mexico. The British guessed that the German Embassy in Washington would relay the message by commercial telegraph. So the Mexican telegraph office would have the ciphertext. "Mr. H.", a British agent in Mexico, bribed an employee of the commercial telegraph company for a copy of the message. (Sir Thomas Hohler, then British ambassador in Mexico, claims to have been Mr. H in his autobiography.) This ciphertext could be passed to the Americans without embarrassment.

The retransmission was enciphered using cipher 13040, which Britain had captured a copy of in Mesopotamia. So by mid-February the British had the complete text.

The second problem was solved by a cover story: that the Telegram's deciphered text had been stolen in Mexico. (The U.S. was informed of the deciphering, but backed up the cover story.) The German government refused to consider a possible code break, and instead sent von Eckardt on a witch-hunt for a traitor in the embassy in Mexico.

The Telegram, completely decrypted and translated.

British use of the Telegram

On February 19, "Blinker" Hall, the head of Room 40, showed the Telegram to the secretary of the U.S. Embassy in Britain, Edward Bell. Bell was at first incredulous, thinking it was a forgery, then enraged. On February 20 Hall informally sent a copy to U.S. ambassador Walter Page. On February 23, Page met with Foreign Minister Balfour, and was given the ciphertext, the message in German, and the English translation. Then Page reported the story to President Woodrow Wilson, including details to be verified from telegraph company files in the U.S.

Effect in the United States

Popular sentiment in the United States at that time was anti-Mexican as well as anti-German, while Mexico was anti-American and in some cases, anti-European. General John J. Pershing had long been chasing the revolutionary Pancho Villa, who had carried out several cross-border raids. News of the Telegram further inflamed tensions between the U.S. and Mexico.

At first, the Telegram was widely believed to be a forgery perpetrated by British intelligence. This belief, which was not restricted to pacifist and pro-German lobbies, was promoted by German and Mexican diplomats, and by some American papers, especially the Hearst press empire. However, first on March 3, 1917 and later on March 29, 1917, Arthur Zimmermann himself admitted that the Telegram was genuine.

On February 1, Germany had resumed "unrestricted" submarine warfare, which caused many civilian deaths, including American passengers on British ships. This caused widespread anti-German sentiment. The Telegram greatly increased this feeling. Besides the highly provocative anti-U.S. proposal to Mexico, the Telegram also mentioned "ruthless employment of our submarines."

United States declares war against Germany

Wilson responded by asking Congress to arm American ships so that they could fend off potential German submarine attacks. A few days later, on April 2, 1917, Wilson asked Congress to declare war on Germany. On April 6, 1917, Congress complied, bringing the United States into World War I.

The telegram was not the only reason for the U.S. entry into the war. Previously, German U-boats had sunk US ships or ships which carried US citizens, of which the most well known was the RMS Lusitaniamarker, torpedoed off the coast of Irelandmarker in May 1915. US ships sunk, less well known, were the SS Housatonic in Feb 1917 in the Bay of Biscaymarker, and the SS California off the Irish coast. It was perceived as especially perfidious that the Telegram was sent to the German embassy in Washington via the U.S. embassy in Berlin and the U.S.-operated cable from Denmark (in fact, that was the only relatively sure channel left to the Germans to communicate to their diplomats in Mexico). Once the American public believed the Telegram to be real, it was all but inevitable that the U.S. would join the Great War.

Historical post-script

In October 2005, it was revealed that an original typescript of the deciphered Zimmermann Telegram had recently been discovered by an unnamed historian who was researching and preparing an official history of the United Kingdom’s Government Communications Headquartersmarker (GCHQ). The document is believed to be the actual telegram shown to the American ambassador in London in 1917. Marked in Admiral Hall's handwriting at the top of the document are the words: "This is the one handed to Dr Page and exposed by the President." Since many of the secret documents in this incident had been destroyed, it had previously been assumed that the original typed "decrypt" was gone forever. However, after discovery of this document, the GCHQ official historian said: "I believe that this is indeed the same document that Balfour handed to Page."



  • Beesly, Patrick (1982). Room 40: British Naval Intelligence, 1914—1918, New York: Harcourt, Brace, Jovanovich. ISBN 0-15-178634-8
  • Bernstorff, Count Johann Heinrich (1920). My Three Years in America, New York: Scribner’s. pp. 310-311.
  • Friedman, William F., and Mendelsohn, Charles J. [1938] (1994). The Zimmermann Telegram of January 16 1917 and its Cryptographic Background, Laguna Hills, CA: Aegean Park Press.
  • Hopkirk, Peter (1994). On Secret Service East of Constantinople, Oxford University Press. ISBN 0-19-280230-5
  • Pommerin, Reiner (1996). "Reichstagsrede Zimmermanns (Auszug), 30. März 1917", in: Quellen zu den deutsch-amerikanischen Beziehungen, Darmstadt: Wissenschaftliche Buchgesellschaft. Vol. 1, pp. 213-216.
  • Singh, Simon The Zimmermann Telegram
  • Tuchman, Barbara W. (1958). The Zimmermann Telegram, Ballantine Books. ISBN 0-345-32425-0
  • West, Nigel (1986). The SIGINT Secrets, William Morrow & Co/Quill. ISBN 0-688-09515-1
  • London Daily Telegraph, 17 October 2005. " Telegram that brought US into Great War is Found". Article by Ben Fenton.
  • Massie, Robert K. (2004). Castles of Steel, Vantage Books, London, 2007. ISBN 978-0-099-52378-9

Further reading
  • Dugdale, Blanche (1937). Arthur James Balfour, New York: Putnam’s. Vol. II, pp. 127-9.
  • Hendrick, Burton J. [1925] (July 2003). The Life and Letters of Walter H. Page, Kessinger Publishing. ISBN 0-7661-7106-X
  • Kahn, David [1967] (1996). The Codebreakers, New York: Macmillan.
  • Katz, Friedrich (1981). The Secret War in Mexico, University of Chicago Press. ISBN 0-226-42589-4
  • Link, Arthur S. (1965) Wilson, Vol. 5, Princeton, NJ: Princeton University Press. Pages 433-5.
  • Winkler, Jonathan Reed (2008) "Nexus: Strategic Communications and American Security in World War I," Cambridge, MA: Harvard University Press. ISBN 978-0674028395


  1. Massie, Robert K., Castles of Steel, pp.516-18, 527, 542, 548, 714.
  2. Room 40
  3. Larger image of the telegram
  4. Perception of the Telegram in the U.S.
  5. Timeline of WW1

External links

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