The Spartans and the Romans
Steganography was sometimes combined with simple means of encryption. It was the Spartans, the most warlike of the Greeks, who established the first system of military cryptography. They invented a device called Skytale, which consists of a staff of wood and a strip of papyrus, leather or parchment wrapped around it. The secret message is written on the parchment from left to right and then unwound. The disconnected letters on the strip does not make sense unless it is rewrapped around a staff of the same thickness as the first.
The first attested use of substitution ciphers come from the Romans. That’s where the name of the well-known Caesar Cipher comes from. Julius Caesar wrote his messages in a cipher, in which the plaintext letters were replaced by letters standing three places further down the alphabet, D for A, E for B, etc. Thus CAESAR would be enciphered to FDHVDU. Just try it yourself at codebrkr.infopages.net/caesar.htm!