Knitting seems like an unlikely companion to espionage. Yet during the World Wars, a pair of needles and a ball of wool could provide something every spy needed: a reason to look completely ordinary.
Knitting was everywhere during wartime. Women were encouraged to make socks, scarves and other clothing for soldiers, so someone sitting beside a railway line with needles in her hands attracted little suspicion. That made knitting a useful cover for observing enemy movements.
There are also documented accounts of knitting being used to encode information. The basic knit and purl stitches provided two contrasting forms that could be arranged as a simple code, somewhat like the dots and dashes of Morse code. Other techniques, such as deliberately dropping a stitch to create a hole, could represent particular pieces of information. During the Second World War, the Belgian Resistance is reported to have used knitting by women watching railway traffic to record the movements and types of German trains.
One of the most remarkable wartime figures connected with knitting was British secret agent Phyllis Latour Doyle. In 1944, she parachuted into occupied Normandy for the Special Operations Executive (SOE). She carried coded information concealed in a silk thread wound around a knitting needle and hidden in a shoelace that she wore in her hair. She later recalled that she had thousands of codes available and used a pinprick to mark those that had already been used.
But there is a distinction worth making. Popular stories sometimes claim that spies routinely knitted complete messages directly into sweaters and scarves. Such techniques were certainly conceivable, and contemporary sources discussed codes hidden in knitting, but historians have found the evidence for some of these dramatic stories difficult to verify. Knitting was often more valuable as camouflage and a way of concealing or carrying information than as a sophisticated secret-writing system.
That may actually make the story more interesting. Espionage did not always require gadgets, disguises or secret laboratories. Sometimes it required simply looking harmless.
And during wartime, few things looked more harmless than someone quietly knitting.