Zimmermann Telegram (or Zimmermann Note or Zimmerman Cable) was a
secret diplomatic communication issued from the German Foreign Office
in January 1917 that proposed a military alliance between Germany and
Mexico in the prior event of the
United States entering World War I
Mexico would recover Texas, Arizona, and New Mexico.
The proposal was intercepted and decoded by British intelligence.
Revelation of the contents enraged American public opinion, especially
after the German Foreign Secretary
Arthur Zimmermann publicly admitted
the telegram was genuine on March 3, and helped generate support for
United States declaration of war on Germany in April. The
decryption was described as the most significant intelligence triumph
for Britain during World War I, and one of the earliest occasions
on which a piece of signals intelligence influenced world events.
2 Mexican response
3 British interception
4 Effect in the United States
5 Previous German efforts to promote war
6 See also
8 Further reading
9 External links
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The message came in the form of a coded telegram dispatched by Arthur
Zimmermann, a Staatssekretär (i.e. a top level civil servant) in the
Foreign Office of the
German Empire on 19 January 1917. The message
was sent to the German ambassador to Mexico, Heinrich von Eckardt.
Zimmermann sent the telegram in anticipation of the resumption of
unrestricted submarine warfare by Germany on 1 February, an act the
German government presumed would almost certainly lead to war with the
United States. The telegram instructed Ambassador Eckardt that if the
United States appeared certain to enter the war, he was to approach
the Mexican Government with a proposal for military alliance with
funding from Germany.
The decoded telegram is as follows:
We intend to begin on the first of February unrestricted submarine
warfare. We shall endeavor 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
Zimmermann Telegram was part of an effort carried out by the
Germans to postpone the transportation of supplies and other war
materials from the
United States to the Allies of
World War I
World War I that
were at war with Germany. The main purpose of the telegram was to
make the Mexican government declare war on the
United States in hopes
of tying down American forces and slowing the export of American
arms. The German High Command believed they would be able to defeat
the British and French on the Western Front and strangle Britain with
unrestricted submarine warfare before American forces could be trained
and shipped to Europe in sufficient numbers to aid the Allies. The
Germans were encouraged by their successes on the Eastern Front into
believing that they would be able to divert large numbers of troops to
the Western Front in support of their goals.
Venustiano Carranza assigned a military commission
to assess the feasibility of the Mexican takeover of their former
territories contemplated by Germany. The generals concluded that it
would be neither possible nor even desirable to attempt such an
enterprise for the following reasons:
Mexico was in the midst of a civil war and Carranza's position was far
from secure. A declaration of war by his regime would have provided an
opportunity for opposing factions to align with the U.S. and Allied
Powers in exchange for diplomatic recognition. More importantly, the
United States was far stronger militarily than
Mexico was. Even if
Mexico's military forces were completely united and loyal to a single
regime, no serious scenario existed under which they could win a war
against the United States.
Germany's promises of "generous financial support" were very
unreliable. The German government had already informed Carranza in
June 1916 that they were unable to provide the necessary gold needed
to stock a completely independent Mexican national bank. Even if
Mexico received financial support, the arms, ammunition, and other
needed war supplies would presumably have to be purchased from the ABC
nations (Argentina, Brazil, and Chile), which would strain relations
with them, as explained below.
Even if by some chance
Mexico had the military means to win a conflict
United States and reclaim the territories in question,
Mexico would have severe difficulty accommodating and/or pacifying a
large English-speaking population that was better supplied with arms
than most civilian populations.
Other foreign relations were at stake. The
ABC nations organized the
Niagara Falls peace conference
Niagara Falls peace conference in 1914 to avoid a full-scale war
United States and
Mexico over the
United States occupation
of Veracruz. If
Mexico were to enter war against the United States, it
would strain relations with those nations.
The Carranza government was recognized de jure by the
United States on
31 August 1917 as a direct consequence of the Zimmermann telegram,
since recognition was necessary to ensure Mexican neutrality in World
War I. After the military invasion of Veracruz in 1914, Mexico
would not participate in any military excursions with the United
States in World War I, thus ensuring Mexican neutrality was the
best outcome that the
United States could hope for, even if Mexican
neutrality would allow German companies to keep their operations in
A portion of the Telegram as decrypted by British Naval Intelligence
codebreakers. The word
Arizona was not in the German codebook and thus
had to be split into phonetic syllables.
The telegram was sent to the German embassy in the
United States for
re-transmission to Eckardt in Mexico. It has traditionally been
claimed that the telegram was sent over three routes: transmitted by
radio and also sent over two trans-Atlantic telegraph cables operated
by neutral governments (the
United States and Sweden) for the use of
their diplomatic services. But it has been established that only one
method was used. The message was delivered to the United States
Embassy in Berlin and then transmitted by diplomatic cable first to
Copenhagen and then to London for onward transmission over
transatlantic cable to Washington. The misinformation about the
"three routes" was spread by William Reginald Hall, then the head of
Room 40, to try to conceal from the
United States the fact that Room
40 was intercepting its cable traffic.
Direct telegraph transmission of the telegram was not possible because
the British had cut the German international cables at the outbreak of
war. However, the
United States allowed limited use of its diplomatic
cables for Germany to communicate with its ambassador in Washington.
The facility was supposed to be used for cables connected with
President Woodrow Wilson's peace proposals.
The Swedish cable ran from Sweden, and the
United States cable from
United States embassy in Denmark. However, neither cable ran
directly to the United States. Both cables passed through a relay
station at Porthcurno, near Land's End, the westernmost tip of
England. Here the signals were boosted for the long trans-oceanic
jump. All traffic through the
Porthcurno relay was copied to British
intelligence, in particular to the codebreakers and analysts in Room
40 at the Admiralty. After their telegraph cables had been cut,
the German Foreign Office appealed to the
United States for use of
their cable for diplomatic messages. President Wilson agreed to this,
in the belief that such cooperation would sustain continued good
relations with Germany, and that more efficient German-American
diplomacy could assist Wilson's goal of a negotiated end to the war.
The Germans handed in messages to the
United States embassy in Berlin,
which were relayed to the embassy in
Denmark and then to the United
States by American telegraph operators. However, the United States
placed conditions on German usage, most notably that all messages had
to be in clear (i.e., uncoded). The Germans assumed that the United
States cable was secure and used it extensively.
Obviously, Zimmermann's note could not be given to the United States
in clear. The Germans therefore persuaded Ambassador James W. Gerard
to accept it in coded form, and it was transmitted on 16 January
In Room 40,
Nigel de Grey had partially deciphered the telegram by the
Room 40 had previously obtained German cipher documents,
including the diplomatic cipher 13040 (captured in the Mesopotamian
campaign), and naval cipher 0075, retrieved from the wrecked cruiser
SMS Magdeburg by the Russians, who passed it to the British.
Disclosure of the Telegram would obviously sway public opinion in the
United States against Germany, provided the Americans could be
convinced it was genuine. But
Room 40 chief
William Reginald Hall
William Reginald Hall was
reluctant to let it out, because the disclosure would expose the
German codes broken in
Room 40 and British eavesdropping on the United
States cable. Hall waited three weeks. During this period, Grey and
cryptographer William Montgomery completed the decryption. On 1
February Germany announced resumption of "unrestricted" submarine
warfare, an act which led the
United States to break off diplomatic
relations with Germany on 3 February.
The Telegram, completely decrypted and translated
Hall passed the telegram to the Foreign Office on 5 February, but
still warned against releasing it. Meanwhile, the British discussed
possible cover stories: to explain to the Americans how they got the
ciphertext of the telegram without admitting to their ability to
intercept American diplomatic communications (which they would
continue to do for another twenty-five years); and to explain how they
got the cleartext of the telegram without letting the Germans know
their codes were broken. Furthermore, the British needed to find a way
to convince the Americans the message was not a forgery.
For the first story, the British obtained the ciphertext of the
telegram from the Mexican commercial telegraph office. The British
knew 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, claimed to have been
"Mr. H", or at least involved with the interception, in his
autobiography.) This ciphertext could be shown to the Americans
without embarrassment. Moreover, the retransmission was enciphered
using the older cipher 13040, so by mid-February the British had not
only the complete text, but also the ability to release the telegram
without revealing the extent to which the latest German codes had been
broken—at worst, the Germans might have realized that the 13040 code
had been compromised, but weighed against the possibility of United
States entry into the war, that was a risk worth taking. Finally,
since copies of the 13040 ciphertext would also have been deposited in
the records of the American commercial telegraph, the British had the
ability to prove the authenticity of the message to the United States
As a cover story, the British could publicly claim that their agents
had stolen the telegram's deciphered text in Mexico. Privately, the
British needed to give the Americans the 13040 cipher so that the
United States government could verify the authenticity of the message
independently with their own commercial telegraphic records; however
the Americans agreed to back the official cover story. The German
Foreign Office refused to consider a possible code break, and instead
sent Ambassador Eckardt on a witch-hunt for a traitor in the embassy
in Mexico. (Eckardt indignantly rejected these accusations, and the
Foreign Office eventually declared the embassy exonerated.)
On 19 February, Hall showed the Telegram to Edward Bell, secretary of
United States Embassy in Britain. Bell was at first incredulous
and thought it to be a forgery. Once Bell was convinced the message
was genuine, he became enraged. On 20 February, Hall informally sent a
United States Ambassador Walter Hines Page. On 23 February,
Page met with British Foreign Minister Arthur Balfour and was given
the ciphertext, the message in German, and the English translation.
Page then reported the story to President Woodrow Wilson, including
details to be verified from telegraph company files in the United
States. Wilson released the text to the media on 28 February 1917.
Effect in the United States
1917 political cartoon about the Zimmermann Telegram
Popular sentiment in the
United States at that time was anti-Mexican
as well as anti-German, while in
Mexico there was considerable
anti-American sentiment. General
John J. Pershing
John J. Pershing had long been
chasing the revolutionary
Pancho Villa and carried out several
cross-border raids. News of the telegram further inflamed tensions
United States and Mexico.
On the other hand, there was also a notable anti-British sentiment in
the United States, particularly among German- and Irish-Americans.
Many Americans wished to avoid the conflict in Europe. Since the
public had been told (untruthfully) that the telegram had been stolen
in a deciphered form in Mexico, the message was widely believed at
first to be an elaborate 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 newspapers, especially the Hearst press empire. This
presented the Wilson administration with a dilemma. With the evidence
United States had been provided confidentially by the British,
Wilson realized the message was genuine—but he could not make the
evidence public without compromising the British codebreaking
Any doubts as to the authenticity of the telegram were removed,
Arthur Zimmermann himself. First at a press conference on
3 March 1917, he told an American journalist, "I cannot deny it. It is
true." Then, on 29 March 1917, Zimmermann gave a speech in the
Reichstag in which he admitted the telegram was genuine.
Zimmermann hoped Americans would understand the idea was that Germany
would only fund Mexico's war with the
United States in the prior event
of American entry into World War I.
On 1 February 1917, Germany began unrestricted submarine warfare
against all ships in the Atlantic bearing the American flag, both
passenger and merchant ships. Two ships were sunk in February, and
most American shipping companies held their ships in port. Besides the
highly provocative war proposal to Mexico, the telegram also mentioned
"ruthless employment of our submarines." Public opinion demanded
action. Wilson had previously refused to assign US Navy crews and guns
to the merchant ships. However, once the Zimmermann note was public,
Wilson called for arming the merchant ships, but anti-war elements in
United States Senate blocked his proposal.
Previous German efforts to promote war
Germany had long sought to incite a war between
Mexico and the United
States, which would have tied down American forces and slowed the
export of American arms to the Allies. The Germans had engaged in
a pattern of actively arming, funding and advising the Mexicans, as
shown by the 1914 Ypiranga Incident and the presence of German
advisors during the 1918 Battle of Ambos Nogales. The German Naval
Franz von Rintelen
Franz von Rintelen had attempted to incite a war
Mexico and the
United States in 1915, giving Victoriano Huerta
$12 million for that purpose. The German saboteur Lothar Witzke
— responsible for the March 1917 munitions explosion at the Mare
Island Naval Shipyard in the San Francisco Bay Area, and possibly
responsible for the July 1916
Black Tom explosion
Black Tom explosion in New Jersey —
was based in
Mexico City. The failure of
United States troops to
Pancho Villa in 1916 and the movement of President Carranza in
favor of Germany emboldened the Germans to send the Zimmermann
The German provocations were partially successful. Woodrow Wilson
ordered the military invasion of Veracruz in 1914 in the context of
Ypiranga Incident and against the advice of the British
government. War was prevented thanks to the Niagara Falls peace
conference organized by the ABC nations, but the occupation was a
decisive factor in Mexican neutrality in World War I. Mexico
refused to participate in the embargo against Germany and granted full
guarantees to the German companies for keeping their operations open,
Mexico City. These guarantees lasted for
twenty-five years — coincidentally, it was on 22 May 1942 that
Mexico declared war on the
Axis Powers following the loss of two
Mexican-flagged tankers that month to
Kriegsmarine U-boats. Woodrow
Wilson considered another military invasion of Veracruz and Tampico in
1917–1918, so as to take control of the Tehuantepec Isthmus
and Tampico oil fields, but this time the relatively new
Venustiano Carranza threatened to destroy the oil
fields in case the Marines landed there. The government of
Japan, another nation mentioned in the Zimmerman Telegram, was already
involved in World War I, on the side of the Allies against Germany,
and later released a statement that Japan was not interested in
changing sides and attacking America.
In October 2005, it was reported that an original typescript of the
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 Headquarters
(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 the discovery of this document, the GCHQ
official historian said: "I believe that this is indeed the same
document that Balfour handed to Page."
World War I
World War I portal
United States portal
American entry into World War I
Imperial German plans for the invasion of the United States
Mexico in World War I
^ Andrew, p. 42.
^ a b "Why was the Zimmerman Telegram so important?". BBC. 17 January
2017. Retrieved 17 January 2017.
^ a b "The telegram that brought America into the First World War".
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^ Katz, p. 364
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^ Polmar & Noot
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Falls, 1914, p. 35, University of Ottawa, Canada.
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Mexico and Its Heritage, p. 596, Greenwood
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United States in the Oil
Controversy, 1917–1942, p. 44, University of
Texas Press, U.S.
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