Many codes are unbreakable (or are effectively so) if you only use them once, statistical attacks become possible with multiple messages. In this case if you s

Many codes are unbreakable (or are effectively so) if you only use them once, statistical attacks become possible with multiple messages. In this case if you send two messages of the same length with the same code both can be broken. Also it's a rearrangement of the letters in the message. So a short message with distinct letters like 'Invade Pyatigorsk' could be easily cracked without knowing the code.