The Great Wall of China - Military Facts of the Great Wall of China The Great Wall would be completely usesless if troops can not rapidly move on it to defend it. As the Great Wall is long, relatively large amount of troops were needed to defend it. During the Ming dynasty (1368-1644 A.D) the Great Wall was defended by a giant force deployed throughout its length. According to figures for the period between 1573 A.D. and 1619 A.D. the total number of troops deployed was around 860,000. Stationing sufficient troops were mostly impractical, because many sections of the wall were in desolate places, so food and quarters had to be supplied via narrow paths to the wall where they are pulled over or slided up in baskets. So the alertness and mobility of troops on the wall plays a critical role in the defence game. Because it is crucial to accurately know when and how much troops to mobile at a time, complicated communication codes have been developed for this purpose. In those pre-electricity days, there are mainly 2 ways of transmitting messages, by hourse carrying mail or smoke and fire. Where the Great Wall of China was built, the terrain is rough and steep which makes horse riding impractical. Thus fire and smoke were the most efficient ways for communications. Along the wall, there were many signal towers (from a few hundred meters apart to a few kilometers apart) built in order to rapidly transmit accurate military message. Normally fire was used at night and smoke during the day for visiblility. Because signaling systems are classified as top military secrets, few of them are completely recovered. There are 2 sets of signals used to inform friendly force enemy information that we are quite familiar with. One set of signals to indicate enemy action (e.g. enemy attacking wall, enemy on the wall etc.), the other to give indications of enemy strength (a single shot and a single fire or smoke signal implies about 100 enemies, two shots and two signals warned of five hundred, three shots and three signals warned of over a thousand and so on) The first set of communication singals were implemented as early as the Warring States period (475-221 B.C.). The system used flagging and beacon fires and drum beats to indicate enemy action. No.of drum beats No.of flags/fire Message 3 1 Enemy reached moat 4 2 Enemy already in moat 5 3 Enemy reached our forward positions 7 5 Enemy reached outer wall 8 6 Enemy reached inner wall Non-stop drum beat Enemy already on wall The Ming dynasty used a different system to indicate enemy strength. No.of enemy troops No. of smoke/fire No. of cannon fire 100 1 1 500 2 2 1,000 3 3 over 5,000 5 5 The Great Wall of China References: The Wall's Unique Communications System

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