World War I: Codebreakers!

By ALLISON HARRELL
Texian Time Machine & Outreach Coordinator

World War I saw the rise of the national agencies dedicated to breaking codes. While most nations had their own code systems and code breakers, a few Allied nations had notable agencies. The British had two code-breaking agencies: Ml 1 and Room 40. Room 40 had both highs and lows during the war. This naval code-breaking branch was responsible for deciphering the Zimmerman telegraph. This telegraph was sent from Germany to Mexico (though it was intercepted along the way) and it promised Mexico parts of the United States if Mexico would help Germany. The contents of this telegraph ultimately spurred the United States into entering World War I. Room 40's success with this telegraph was overshadowed by the naval mess that developed later between the German and British navy. The British were intercepting and decoding German orders, but the orders themselves were wrong (and the Germans were just as confused as the British). The British navy blamed the bad orders on Room 40, and didn't trust the code-breaking branch after that.

The American code-breaking agency was led by a man named Herbert Yardley (1889-1958), but his biggest inspiration actually came from the French. The French code-breaking agency employed a man named Georges Painvin. Before World War I, Painvin worked as a professor of geology and paleontology. After the war started, through a series of chance encounters and a few cases of just knowing the right people, Painvin ended up in the code-breaking agency. Painvin's claim to fame was cracking the German ADFGVX cipher.
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Unlike the British, Painvin did not have the luxury of having a German code book on hand. He cracked the complex checkerboard code by hand and turned the tide on the German offensive against Paris. During the grueling process of deciphering this code, Painvin lost more than 30 pounds.

Code-Breakers: It's Your Turn!

• Download the Substitution Code Worksheet
• Download the Checkerboard Code Worksheet
• Download the Answers to the Riddles!