One of the most important parts of a POW's life was communicating with his fellow captives. The first communication between isolated prisoners of war may have been a name scrawled on a piece of toilet ...

The first three codes, known as K1, K2 and K3, were solved as far back as 1999 by the CIA’s own codebreakers. Jarett Kobek, a journalist, author and amateur codebreaker based in California, asked ...