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The text above is Morse code. It uses only two characters, often referred to as “dots” and “dashes,” as its entire character set. With just these two characters, we can communicate full sentences with relative ease. (You can translate that here if you’d like, but the message isn’t all that interesting.) It’s not the most efficient way to communicate, at least not nowadays, but it does the job. It demonstrates that you don’t need 26 or so letters to communicate a complete thought.
And during World War II, that principle — combined with a large helping of age-based stereotyping — helped the Allies in their battle against the Germans.
The German occupation of Belgium began in May of 1940 and lasted until February of 1945. During that nearly five-year period, many Belgians took it upon themselves to resist the occupying forces, whether it be through violent tactics (such as sabotage or assassination) or via nonviolent measures like underground, anti-Nazi newspapers. And of course, there was also espionage.
As the Germans exploited Belgium more and more, they also exposed information to the people in the Resistance; for example, it’s pretty hard to hide a train as it comes into or leaves a station. An enterprising member of the Resistance could record information about the trains — were they carrying troops or were they supply trains? — and then pass it onto the Allies. But he or she would have to do so secretly; if the Germans caught wind of the effort or, even worse, found the reversed-engineered train schedules, there’d be blood spilled.
Which is why the Belgian Resistance tapped into a small network of grandmothers to knit some clothes.
Knitting, in a sense, uses a binary language kind of like Morse code, only with yarn. As Atlas Obscura explains, “every knitted garment is made of different combinations of just two stitches: a knit stitch, which is smooth and looks like a ‘v’, and a purl stitch, which looks like a horizontal line or a little bump.” As a result, one could rather easily turn a stitching pattern into code, with knit stitches as the dots (for example) and purls as the dashes. And that’s exactly what happened. Atlas Obscura continues: “By making a specific combination of knits and purls in a predetermined pattern, spies could pass on a custom piece of fabric and read the secret message, buried in the innocent warmth of a scarf or hat.”
And if you think about it, knitting grandmothers make for really great spies — no one is going to think twice about an older woman sitting on her balcony armed with some knitting needles, a big ball of yarn, and a half-made scarf hanging off to the side. So, per knitting newsletter Handwoven, “the Belgian Resistance during World War II recruited women who had windows overlooking railway yards. They were to note the German train movements with their knitting: Purl one for one type of train, drop one [knit stitch] for another.”
How important the knitting grandmothers were to the war effort was never quantified, but it’s safe to say that the British, at least, respected the concept of sweaters with encoded messages. As QI explained, “British censors banned anything which might be used to convey secret messages from being sent through the international mail” — a ban that included knitting patterns.
From the Archives: War Games: Another secret code from World War II.