"During World War I, the German military used a double columnar transposition cipher, changing the keys infrequently. The system was regularly solved by the French, naming it Übchi, who were typically able to quickly find the keys once they'd intercepted a number of messages of the same length, which generally took only a few days. However, the French success became widely known and, after a publication in Le Matin,
the Germans changed to a new system on 18 November 1914. [1]"https://en.wikipedia.org/wiki/Double_transposition_cipher#Do...
Courtesy of M. Édouard Snoden.