Today (January 17) in London History – Turning Point in World History

Today’s the anniversary of the decoding of the Zimmerman Telegram, a turning point in world history. Happened in London on January 17, 1917.


London Calling.

So much history in London.

I’m thinking today of Room 40 in the Old Admiralty Building. 

Something that happened there on this day in 1917.

Ok, let’s throw the light switch. 

On January 17th, 1917 the Zimmerman telegraph was decoded in Room 40 of the Old Admiralty Building.

The Zimmerman telegraph was political dynamite. It led directly to America’s declaration of war on Germany.

Aside here: this is what I love about being a London Walks guide. Being able to walk by a building and knowing, “so that’s where that happened.”

Ok, let’s put the pieces together – who was Zimmerman? What was the Zimmerman telegraph? Who decoded it? Why Room 40? How did the Brits detonate the dynamite without its going off in their own face?

Zimmerman was Arthur Zimmerman, the German foreign minister. The telegraph was sent from him through the Atlantic cable to the German ambassador in Mexico City. It announced the imminent start of unrestricted submarine warfare in the Atlantic. It instructed the ambassador to approach the Mexican government and invite it to join Germany in an alliance against the United States. It dangled a huge carrot in front of the Mexicans. That huge carrot was the American States of Texas, Arizona, and New Mexico. 

The return of those states to Mexico would be the payoff for siding with Berlin.

Political dynamite.

The only problem was how to go to public with it. London couldn’t come right out and announce it because Germany would then know that its codes were broken – know that London was intercepting and reading the messages Berlin was sending over the Atlantic cable. 

And the problem was even stickier because the obvious implication would be that Britain was also reading the telegrams of neutrals, including the United States.

They pulled the wool over everybody’s eyes by saying they’d stolen a copy of the telegram in Mexico City, after it had been received. They showed it to American diplomats. Said, “look what our people in Mexico City have managed to lay their hands on – you’re not going to like this one bit –  as you can see, Berlin’s planning on giving the American southwest back to Mexico.” Thank you, Zimmerman Telegram. Mission accomplished. American neutrality flushed right down the pan without revealing that American cables were being tapped. Remember, in 1917 there were far more German Americans than there were British Americans. Public opinion wanted America to steer well clear of the European war. President Wilson had formally proclaimed American neutrality.

Overnight the Zimmerman telegram turned American public opinion, the U.S. Congress and the White House in favour of American intervention in the war. American intervention on the side of the Allies, Britain, France and Russia. It’s no exaggeration to say the Zimmerman telegram tipped the balance, made the Allied victory possible. 

Finally, why Room 40? And who was in there that day, who got the job done? Room 40 housed the diplomatic section of the Naval Intelligence Division.

Two men were at the sharp end in there that day. They were Cryptanalysts Nigel Arthur de Grey and Reverend William Montgomery. It’s a piquant detail that both of them had Church of England connections. Reverend Montgomery was a church historian and Nigel Arthur de Grey was born in a rectory, the son of a Suffolk rector. 

And on that note, from London, fare thee well. Hope to see you soon. 

Leave a Reply

Your email address will not be published. Required fields are marked *