The Great wall of China - The Wall’s unique communication system

Continued from: The Great Wall of China - The Farming Garrison

 All the architectural structures along the wall, which I have already mentioned, were of great tactical importance in the wall’s defence system. The section of the wall at Badaling for example, still well preserved was about 22-26 feet in height, 19-22 feet in breadth at the foundation and 10 feet on top, and permitted a pathway for the garrison troops, allowing five cavalryman or ten soldiers to gallop or walk abreast respectively[i]. All along the wall, watchtowers, wall towers and beacon towers had grown in multitudes creating an impressive sight, built at intervals of 300 yards in less dangerous areas and at 100 yards in a more hazardous one; their size varied from the geographically areas in which these towers were built, however, generally measuring 40 feet in height, 40 feet square at the base and 30 feet square at the top.  Similarly to the turrets of a Medieval European castle, in it 30 to 50 men were able to hold up position; stoked with enough provisions, they were able to withstand a four month siege. ‘At the height of the wall’s usefulness there were as many as 25,000 such towers […] as well as several thousand others that were free standing further north as outpost to warn of marauding bands’[ii].  Accuracy was of vital importance in communication matters, any misbehaviour was severely punished:

beacon towers, together with their guards, must be inspected regularly.  Stocks must be stored in quantity, and lookouts placed around the clock.  In case of emergency, raise smoke in the daytime, or light a fire by night, to pass on the alert.  See to it that no damage is done to the towers, so as to ensure prompt communication.  Those who convey the information quickly and help defeat the enemy will be rewarded. Violators shall be punished according to military law.[iii] 

The soldiers on guard at the beacon tower were obliged also to reconnoitre the terrain, safeguarding the terrain lands reclaimed by the garrison troops, checking and protecting the passing trade caravans, supporting troops during attacks.  From Ch’in’s period to the later Ming one, an accurate system of communication with specific guidelines was drawn up and significantly improved during the years.  While in the early centuries only beacon fires and drums were used to warn the approach of the enemies, later on flag signals were added:

 

The main signals used from Ch’in’s time and onward were: beacon fires, coloured torches, signals derricks, flags, smoke – wolf dung and sulphur as the preferred burnable material – and drums.

By the Tang dynasty (618-907 A.D.) messages could be conveyed more then 1000 km in 24 hours, compared with only a few hundred kilometres in the earlier days.  With Ming dynasty cannons were also introduced as a means of signalling:

Furthermore, the use of colour smoke or lantern was also added:

Enemy force less than 100: one yellow flag in daytime and one lantern at night.
Enemy force 100-500: one black flag in daytime and two lanterns at night.
Enemy force 500-1,000: a sheepskin hoisted in daytime and three lanterns at night.
Enemy force 5,000-10,000: a long white cloth strip in daytime and four lanterns at night.
Enemy attacking: artillery fire.
Enemy not withdrawing; repeat alarm every two hours[iv].

Secret and urgent messages were delivered by dispatching a courier, who would find fresh horses along his way and 400 km in a day was the record for delivery.  Each of these tower were guarded by a minimum of 3 soldiers, up to 29 soldiers, and each group had its beacon officer.

(To be finished...)

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[i] Lou Zewen, The Great Wall, McGraw-Hill Book Company, England, 1981, p.145.

[ii] Jonathan Fryer,  The Great Wall of China, New English Library, London, 1975, p. 51.

[iii] Lou Zewen, The Great Wall, McGraw-Hill Book Company, England, 1981, p. 152.

[iv] Ibid