The Dark Crystal Thra

For the vast majority of human history, communication with anybody out of your line of sight was not easy. It took intense time and labor to transmit messages to people who were not in your direct vicinity. The world is so different now that we have basically instantaneous, simultaneous tel communication. We can hash out any potential miscommunications rather quickly without having to send messages back and forth. There are a couple of examples of organized systems of fast moving messengers in history.