Caesar cipher as a secret message

Caesar cipher is a substitution cipher used by Julius Caesar in 58 BC. hence it is now referred to as caesar cipher. 

Caesar shifted each letter in his military orders to make the message seem meaningless. And make the enemy think should they intercept it? An example is like when we want to send a message to our friend. We shift each letter from its original letter, for example 3 letters from A to D. This shift must of course be the result of the agreement of both parties. When the message is sent and reaches our friend, our friend must translate it to the original message, which is shifting 3 letters backwards. This basic chip was used by military leaders for hundreds of years after the emperor. But a key is only as strong as its weakest point. The weakness of Caesar's cipher was publicised 800 years ago by Al Kindi, an Arabic mathematician, who cracked Caesar's cipher using clues based on important properties of the language used to write the message. This discovered frequency analysis was a blow to the security of the Caesar chiper cipher.