I did not know this story, this is fascinating!!! WOW

These photos are of World War I cryptographers trained by William and Elizebeth Friedman, in Aurora, Illinois, early 1918. By facing either forward or sideways, the soldiers formed a coded phrase using Francis Bacon’s biliteral cipher. The intended message was the Baconian motto “Knowledge is power,” but there were insufficient people to complete the r (and the w was compromised by one soldier looking the wrong way).

Learn more : https://www.youtube.com/watch?v=4C9phKLx2vU