@eibart @grimalkina yeah it’s pretty cool, although since all articles use the example of the Belgian women tracking trains I don’t think it was very widespread. And most people would definitely notice something was up with the fabric, it would look quite wobbly :)
For the people reading along who prefer English, this one is almost identical (although it says “dropped stitch” where I think they mean “yarn over”) www.atlasobscura.com/articles/knitting-spies-wwi-wwii