Zimmermann’s telegram. How the United States entered World War I

Arthur Zimmerman. Photo Wikimedia Commons

After the outbreak of the First World War, official Washington declared neutrality. The United States did not enter the war in principle and maintained relations with all its participants. However, at the beginning of 1917, British intelligence learned about new German plans. She intercepted the so-called. Zimmermann’s telegram, which described possible ways of cooperation between Germany and Mexico against the United States.

Your worries

With the outbreak of World War I, the United States declared itself a neutral country. They continued to maintain relations and cooperate with the belligerent powers, but did not intend to enter the war. From time to time, such proposals appeared, but they were all rejected.

At that time, Washington had enough of its own worries, which simply did not allow joining the hostilities in Europe. The total number of the army and the national guard barely exceeded 300 thousand people, and they did not differ in high combat effectiveness. In addition, the army was engaged in operations in Mexico and other Latin American countries. In such a situation, it was hardly worth joining the allies overseas.

However, the United States did not stand aside. Quite quickly, they became the “workshop of the Entente” and began to supply the belligerent countries with military products – with good benefits for themselves. Relations with Germany were limited to diplomatic communication, but after the sinking of the steamer Lusitania and hundreds of American citizens, the situation worsened. Calls to join the Entente and begin an armed struggle with Germany were heard again.

Encrypted telegram transmitted by the German ambassador to the United States to the ambassador in Mexico. Photo US National Archives / catalog.archives.gov

Cooperation offer

At the end of 1916, against the background of a general deterioration in the situation, the State Secretary (Minister) of Foreign Affairs of Germany, Arthur Zimmermann, developed a plan in case the United States entered the war. The key idea behind this plan was to involve Mexico, already in confrontation with Washington.

According to the Zimmermann plan, Mexico was to start active hostilities against the United States in exchange for financial assistance. In case of victory in Europe, she was promised to transfer the territories previously conquered by the United States. Berlin believed that Mexico would be interested in such a proposal and would soon start an open war. As a result, the American army will be forced to operate near its own borders and will not have enough strength to send it to Europe.

The possibility of making a similar proposal to Japan was also considered. This country, too, could declare war on the United States and ease the situation of Germany. However, the implementation of the Japanese scenario was associated with a host of problems – Tokyo was already on the side of the Entente, and it would be difficult to lure it over to the Central Powers.

In mid-January 1917, the main theses of the plan were drawn up in the form of a telegram for the Ambassador to Mexico, Heinrich von Eckhard. Now the documents had to be sent to the addressee and wait for a response from a foreign state.

Difficulties in shipping

Before the war, Germany had a developed telegraph network and a number of submarine cables, which made it possible to maintain communication with many countries, incl. in both Americas. However, with the outbreak of war, Britain destroyed this infrastructure, and sending diplomatic mail was now extremely difficult, especially to the other hemisphere.

Cryptanalyst Working Papers. Photo Wikimedia Commons

The telegram for H. von Eckhardt had to be sent in a roundabout way with the involvement of foreign infrastructure. One message went through Sweden, on the Stockholm – Buenos Aires line. For the second, they used the American connection and sent the ambassador to the United States, who was supposed to send the document to Mexico as quickly as possible.

Like other diplomatic mail, the Zimmermann telegram was encrypted. This fact, as well as the special approach to its transfer, was believed to have protected from interception, possible decryption and subsequent military-political problems.

British intelligence

British scouts quickly enough managed to intercept the transmission from Stockholm and set about decrypting. By that time, the cryptanalysts from the “Room 40” department had German ciphers at their disposal and easily reconstructed the contents of the telegram. Soon a copy of the document arrived from Mexico, intercepted through the local telegraph service. Britain now had two complementary copies of the secret document.

The “Mexican” telegram was of particular importance. With its help, it was possible to show exactly how British intelligence obtained information. Otherwise, London would have to face accusations of checking someone else’s diplomatic mail – moreover, a neutral country.

Zimmermann to Bernsdorf for Eckhard, no. 1658.

We propose to start the most merciless submarine war on February 1. In doing so, we will try to keep America in a state of neutrality (a number of groups cannot be deciphered). If we fail to do so, we will offer Mexico an alliance on the following terms … Waging war … Making peace …

Your Excellency must at this time inform the President in secret that (a number of groups cannot be deciphered) our submarine fleet will force England to ask us … in the coming months. Confirm receipt.


Translated by R. Bukar. In the depths of the secret archives. – M .: Military Publishing House of the NKO of the USSR, 1938.

Zimmermann’s decoded telegram made London happy. With its help, it was possible to convince Washington to enter the war as a full-fledged belligerent power. By the beginning of 1917, a difficult situation had developed on the European fronts, and the American army could change the situation in favor of the Entente.

Translation of the telegram into English. Photo US National Archives / catalog.archives.gov

On February 19, 1917, the original and the translation of the German encryption were handed over to the American Embassy in Great Britain. The diplomats had to be convinced of the veracity of the message, but soon the corresponding report was sent to Washington.

The public knows

The administration of President Woodrow Wilson did not hide Zimmermann’s telegram and published it, provoking a real scandal. In public and political circles, several opposing opinions were formed both about the document itself and about the required response to it.

Anti-German circles perceived the telegram as direct aggression and demanded to immediately enter the war in order to “punish the treacherous Huns.” The pacifists and pro-German public, in turn, denounced Zimmermann’s telegram as a fake. Society, politicians and the press exchanged opinions, argued and swore for several weeks.

In early March, the unexpected happened. For an unclear reason, Secretary of State for Foreign Affairs A. Zimmerman officially acknowledged plans to involve Mexico and confirmed the sending of a telegram to the German ambassador. First he did it in an interview, and then in a speech in the Reichstag. According to some estimates, this move was one of the reasons for the imminent resignation of Zimmermann. In early August, he left the post of minister.

Woodrow Wilson Addressing Congress, February 3, 1917. Zimmermann’s telegram will soon be known. Photo teachpol.tcnj.edu

Despite the scandal in the United States, Mexico considered the German proposal. The government of President Venustiano Carranza studied the issue and decided not to agree to cooperation. The official Mexico City rightly decided that the declaration of war on the United States threatens with serious military and economic problems. At the same time, the support promised by Berlin looked unlikely and almost useless.

Japan, having learned about the German plans, rejected them. Subsequently, it was announced that it was in the country’s interest to maintain the existing situation. Tokyo planned to remain on the side of the Entente and did not intend to fight the United States.


Shortly before the decryption of the telegram, on February 1, Germany resumed a previously suspended unrestricted submarine war in the Atlantic, aimed at destroying ships and ships flying the American flag.

New disputes began in Washington, which had a natural result. On April 6, 1917, the US Congress approved W. Wilson’s proposal to enter the war. A few months later, the expeditionary force landed in Europe and went into battle on the Western Front – on the side of Great Britain, France, Russia and their allies.

American soldiers fighting in the Argonne Forest, 1918. Several months remain until the end of the war. US Department of Defense Photo

Consequence document

Zimmermann’s plan to involve Mexico in the war on the side of the Central Powers was quite bold and promised serious military-political benefits. With its help, it was planned to leave the United States aside and prevent an enemy from entering Europe capable of providing the Entente with decisive advantages.

However, the implementation of this plan did not go well from the very beginning. The document for the ambassador responsible for negotiations with Mexico immediately fell into the hands of enemy intelligence. The United States learned about Germany’s treacherous plans, and Great Britain and France were able to turn a friendly country into an ally in the war. What happened next is well known. Just a year and a half later, the United States was on the list of winning countries.

It should be noted that the Zimmermann telegram was actually not the only reason for the United States to enter the war. Since 1914, active debates continued about the need for such a step, in which a variety of arguments were presented. In addition, various political and commercial structures promoted their interests through these disputes. As a result, the “war party” became the winner of the dispute. A certain contribution to this development of events was made by the political miscalculation of the German Foreign Office and the success of British intelligence.

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