When you stand on the Great wall, you may wonder “How was the Great wall defended”?
Well, the Great Wall is tall and high, but its defensive function is not just about its strong structures. The defense was primary by archers in ancient time. Since it was not possible to send arches along the whole wall, they set sentries in certain distance to warn against invasions.
The Great Wall of China was defended primarily by archers. Since it was too expensive to keep the Wall perpetually manned, sentries along the length of the walls in use served to warn against impending
invasions. Some enemies might choose to climb the wall, but in this condition, they could not carry any heavy arms.
The most vulnerable section seems to be the gates of the Great wall. It is a necessary facility to trade in and out of China. Those gates are mostly large, with trap between an inner and outer gate or leading into a labyrinth or small fortress.
There are watchtowers dotted every so many miles along the Great Wall, numbering 25,000 in all. Those watchtowers served 2 purposes:
First, sentries could stand on the tower to keep watch for any impending invasion approaching the wall. The towers were built on hilltops which could maximize the sight rang for sentries.
Second, when an attack closed, sentries in the watchtower could light a signal fire, then sentries in other tower could see and send signal by waving flags, rising smoke in the day, lanterns or light in the night. This signal would pass from on watch tower to another until the troops was alerted and ready to fight against the invaders.
There were also soldiers patrolling on the top of the wall from tower to tower. Thus, the Great Wall of China was defended by sentries, a system of signal flags, fires, and lights, and an army who were quick on their feet.
If enemies were very determined, the earlier built Great wall could be broken through the gates. In Ming Dynasty the gates had been enhanced and strong enough to prevent any invasions and it could just be opened from within. Sometimes the Great Wall could not prevent enemy from entering China, but it did at least slow down the attack of the invaders and prevent them bring horses in and goods out.