 History fact number one, did you know that during the construction of the Great Wall of China, a unique communication system was used? The builders employed smoke signals to convey messages along the length of the wall. This system was incredibly efficient for its time. When invaders were spotted, guards at the watchtowers would light fires or set off smoke signals. This alert would then be passed along the wall from tower to tower, rapidly transmitting messages over long distances. This method was so effective that it was used for centuries as a primary means of communication in times of military threat. Share your thoughts and subscribe for more.