Feb. 24, 2023

The Zimmermann Telegram

The Zimmermann Telegram

February 24th, 1917. The British present the Zimmermann Telegram to US President Woodrow Wilson, an intercepted message that reveals new threats against the United States and persuades the nation to enter World War I.


Cold Open

It’s a foggy early morning on August 26th, 1914, just one month into World War I.

A German cruiser cuts through the Baltic Sea, laying mines near the entry to the Gulf of Finland. The SMS Magdeburg works under the cover of the darkness, steaming along… until it comes to a shuddering halt. On deck, the captain curses as the ship runs aground in the shallow waters of a nearby island.

Captain directs his crew to start throwing any unnecessary equipment overboard. He’s confident that if they can lighten the cruiser’s load, it will pull off the shores. But despite their best efforts, the ship doesn’t come free. So left with no choice… the captain orders his crew to start lowering the ship’s dinghies. As the men prepare for evacuation, the captain’s mind goes immediately to the most precious cargo on board: a set of three codebooks used to write and decipher German communications.

Quickly, the captain orders a signalman to fetch the books. But as he awaits the crewmember’s return, he gazes out at the horizon. A break develops in the fog, and the captain sees two unfamiliar vessels bearing down on his boat. As they draw closer, he recognizes them as Russian ships.

As the enemy ships open fire on the Magdeburg, captain rushes to locate the signalman he sent to retrieve the codebooks. When he finds him, the captain orders the signalman to take the books, row out to deep water, and throw them overboard.

The captain looks on as the signalman boards a dinghy with the codebooks in hand, and is slowly lowered down. But before the boat can reach the water below… incoming Russian shells explode all around it. Captain looks on in horror as the signalman is struck and tumbles into the sea, the codebooks still clutched to his chest.

After the briefing counter in the Baltic Sea, the Russians rescue drowning German sailors and the bodies of those that can not be saved. And when they drag aboard one body, still clasped within the dead man’s arms will be the invaluable keys to Germany’s communication system.

The Russians keep two of the three German codebooks they recovered from the SMS Magdeburg. But they pass the other on to the British government. They use it to establish a top-secret code-breaking operation. And armed with the codebook, and others like it they will later seize, British intelligence is able to decipher most German messages. But no intercepted note will be as consequential as the Zimmermann Telegram, an inflammatory document that will persuade the United States to declare war on Germany after its contents are revealed to the US government on February 24th, 1917.


From Noiser and Airship, I’m Lindsay Graham and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is February 24th, 1917: The Zimmerman Telegram Pushes America into World War I.

Act One: The British Interception

It’s the morning of January 17th, 1917 in London, England, two and a half years into World War I.

Inside the Old Admiralty Building, a duty officer for the British Naval Intelligence inspects the first intercepted message of the day: a coded German telegram. The officer tries to decipher the note, but he can’t make it out. So he passes it off to Room 40, the home of the Admiralty’s top-secret codebreaking division.

Inside Room 40, cryptanalysts Nigel de Grey and William Montgomery carefully inspect the coded message. Nigel spreads the document on the table before him, revealing rows and rows of numerals. To the untrained eye, the numbers are nonsensical. But the codebreakers know that within the digits are hidden words waiting to be read.

Still, at first glance, the telegram appears to be nothing special. The only abnormality Nigel notices is the length. It's long, composed of nearly a thousand individual groups of numbers. But Nigel hardly suspects that it’s anything more than yet another note in a series of recent correspondences between Berlin and Washington.

For a while now, British intelligence has been intercepting messages between the two powers about a negotiated peace. None of their contents have been very surprising. Most reaffirm what the British already know: President Woodrow Wilson is bent on stopping the war by playing peacemaker and that the German-led Central Powers have no interest in compromising with the Allies. British agents suspect that Berlin is only maintaining communication with President Wilson to ensure the US stays neutral and out of the conflict.

So though far from revelatory, the messages are frustrating to British leaders. They don’t want America as a mediator; they want the wealthy and powerful nation as an ally. The War currently raging has already devolved into conflict of attrition. It’s obvious to many within Britain’s army and government that America’s strength and resources will be the key to pushing past the war’s stalemate and securing Allied victory. But time and again, President Wilson has refused to budge, ignoring Britain’s pleas for intervention. So Today, as Nigel and William examine this newest telegram, they anticipate nothing more than a reassertion of well-known sentiments.

The two codebreakers nonetheless get to work deciphering the message. At first, it's difficult but a series of digits soon catches Nigel’s eye: 13042. Nigel recognizes these numbers are part of a German diplomatic code. So he instructs William to open a nearby safe and retrieve the relevant German codebook taken from the SMS Magdeburg.In short order, the cryptanalysts start to uncover the telegram’s hidden message.

First, they decode the sender’s name. It’s one they know well: Germany’s Foreign Minister, Arthur Zimmermann. Then, they turn their attention to the start of the message where they make out that the recipient is the German ambassador to the US. So far, these details are nothing out of the ordinary. But, as they continue on, one word piques their curiosity. Within a coded series of digits, they uncover the word, “Mexico.”

The two agents furrow their brows. They have no idea why the Germans are talking about Mexico, a country that has remained neutral throughout the war. So with a new vigor, Nigel and William continue their work. Soon, they decode the word, “alliance,” and then the phrase, “us and Japan.” The codebreakers look at each other in astonishment. Japan is currently one of the Allied powers. But now, Nigel and William wonder if the country could be switching sides.

Frantically, they get to work unlocking the meaning of the rest of the document. By the end of two hours, they decipher enough code to make two bombshell discoveries. Over a year ago, Germany stopped attacking neutral ships under pressure from the United States. But the telegram reveals that policy is about to change. In just two weeks, Germany intends to resume unrestricted submarine warfare, giving its U-boats permission to attack any ship approaching the war zone, including the vessels of neutral nations. The other surprise is that Germany is trying to form an alliance with America’s neighbor, Mexico, as well as Japan.

These discoveries alone seem momentous enough to help persuade the United States to support the Allies. But the telegram’s most damning revelation is still hidden. Still, within the partially-decoded telegram, there remains one undeciphered passage. Over the next two weeks, the message is fully and laboriously decoded. The missing segment turns out the biggest bombshell of all: Germany not only wants an alliance with Mexico but if they agreed to get in the fight, Germany is promising to assist Mexico in reconquering territory it lost to the United States.

For the British, the Zimmerman Telegram is both horrifying and miraculous. Though it will reveal new perils facing the Allies and the United States, it will also offer a welcome opportunity for Britain to force President Wilson’s hand. For the next month, the British will keep the secret telegram close, waiting for the perfect moment to leverage the document and persuade the United States to finally join them in war.

Act Two: The US Reaction

It’s 8:30 in the evening on February 24th, 1917, in Washington DC.

Inside the State Department’s headquarters, Acting Secretary of State Frank L. Polk’s ears perk at the news that an important telegram has finally arrived.

All day, Polk has been waiting for word from the U.S. ambassador to Britain, Walter H. Page. This morning, Page sent the State Department a telegram saying a message of great importance would arrive within three hours. But the three hours passed, and no communication materialized. So all afternoon, Polk continued to wait. Until now.

When he looks off as a huffing staffer barges into his office, paper in hand. Wordlessly, the staffer hands it to Polk who immediately begins reading its contents. Polk’s brows shoot up as he reads the revelations contained inside the Zimmermann Telegram. Anger bubbles up within him as he realizes the Germans are plotting against the Americans at the same time they’re talking peace with President Woodrow Wilson.

As soon as he finishes digesting the Germans’ plot, Polk rises from his desk and walks across the street to the White House, with the telegram in hand. He knows he can’t wait until morning to share this news with the President.

When hostilities first broke out in Europe in 1914, President Wilson almost immediately declared that America would remain neutral. And, ever since the war’s onset, he has held firm to his stance. Even after German submarines led to the loss of American lives in the sinking of the British steamship Lusitania, the president continued to turn toward diplomacy. And behind him, the American public seems to support his neutral position. Just last year, Wilson successfully ran his re-election campaign with the slogan, “He kept us out of war.”

But the international events have put Wilson’s neutrality to the test. One aspect of the Zimmermann Telegram has already come to pass. On the first of this month, the Germans announced they would be resuming unrestricted submarine warfare. In response, Wilson finally severed diplomatic relations with Germany. Still, the president stopped short of declaring war. Instead, he left the possibility of negotiation open and maintained that America should hold onto the role of peacemaker. But as he steps into the Oval Office, Secretary Polk knows it’s possible that the paper in his hand will spell the end of America’s neutrality.

As the president reads over the Zimmerman telegram, Wilson’s face falls into a deep frown. Privately, the president already favors the democratic Britain over Germany, an authoritarian country. The Germans’ autocratic monarchy runs counter to Wilson’s core belief in self-government. But that is a fact he has mostly kept to himself. Publicly, he has followed his own advice, trying his best to stay neutral in thought, word, and deed. He’s always believed that America’s neutrality is key to lasting world peace. But now, he’s having doubts.

When he finishes reading, Wilson looks up, his eyes ablaze with indignation. Quickly, a new anger overwhelms his long-held sentiments. He wants to expose Germany’s malicious duplicity to the American public, making it clear to them and the rest of the world that Germany is not to be trusted. So impulsively, Wilson suggests that they release the telegram to the press. But secretary Polk pushes back, believing that relations are already too delicate; the government’s response needs to be careful and deliberate. And after some time, Wilson agrees. As the initial shock of the telegram wears off, the president’s typical circumspect attitude returns. But his anger doesn’t leave him, nor does his new sense that America may no longer be able to escape the war in Europe.

Two days later, President Wilson asks Congress to arm American merchant ships in the war zone. When anti-war Senators obstruct the measure from passing, Wilson pushes forward with the plan by circumventing Congress with an executive order. And then one week after receiving the Zimmermann Telegram, Wilson decides to indeed make the secret message public, drumming up support for the possibility of entering the war.

On March 1st, news of the telegram is published by the American press. Headlines decrying a German plot against the US whip the nation into a frenzy. Quickly, public opinion turns against Germany, and in favor of war. It becomes clear to many that the nation is already inching toward conflict, but it still takes the president weeks of deliberation to make his final decision.

For years, Wilson believed that America’s neutrality in World War I would be the key to world peace. But, the threat of Germany has now grown too great. It seems the only way to establish lasting peace is to fight. Still, the cautious and contemplative Wilson remains hesitant. The weight of the inevitable American deaths that would follow a declaration of war weigh heavily on his mind. President knows this is a decision too great to make on his own.

So on March 20th, Wilson meets with his cabinet. He grows solemn as the members unanimously recommend war. The president will leave that meeting without announcing his plans but his mind will be made up. The following day, President Wilson will set a date for a special session of Congress where he will deliver one of the most important speeches of his career and change the course of the First World War.

Act Three: A Call for War

It’s the evening of April 2nd, 1917 at the Capitol Building in Washington DC, less than six weeks after President Woodrow Wilson received the Zimmerman Telegram.

Behind the podium on the floor of Congress, Wilson stands and prepares to deliver what he knows would be the most consequential speech of his career and for the nation. No one in the room knows what the president is about to say. All Wilson has told them about today’s special joint session of Congress is that it regards grave matters of national policy.

A hush falls over the packed chamber as the president begins his speech. He starts by railing against the horror of Germany’s submarine warfare. Wilson asks his Congressional audience to declare the recent course of the imperial German government to be nothing less than war against the United States. He reminds Congress of the disturbing revelations of the Zimmermann Telegram, deeming them evidence of Germany’s true hostile purpose. He then insists that the world must be made safe for democracy.

Many nod along as the president states that neutrality is neither possible nor desirable when it comes to the menace of autocracy. And when Wilson finally asks Congress to declare war on Germany, cheers erupt.

Two days after Wilson’s call for a declaration of war, the Senate votes in support of the measure. Two days after that, the House does the same. Only months later, in June, the first American soldiers will arrive in Europe. Over the course of the next year and a half, millions of Americans at home and abroad will support the war effort. And reinvigorated by new manpower and resources, the Allies will push through the stalemate to finally claim victory on November 11th, 1918 — an outcome set in motion when the Zimmermann Telegram landed on President Wilson’s desk on February 24th, 1917.


Next onHistory Daily. February 27th, 1933. Exactly eight years after he relaunched the Nazis as a political party, German Chancellor Adolf Hitler uses an arson attack on Berlin’s parliamentary building to seize power and purge his political opponents.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Mollie Baack.

Sound design by Derek Behrens. 

Music by Lindsay Graham.

This episode is written and researched by Alexandra Currie-Buckner.

Executive Producers are Steven Walters for Airship, and Pascal Hughes for Noiser.