Was the great wall of china sucessful?
Ultimately, no. It didn’t keep foreigner invaders out, and it didn’t really keep the Chinese in, either. Invading armies, such as the Mongols in the 12th century, either bribed gate garrisons to let them in (not a difficult thing to do, since many garrisons were manned by little more than slave labor), or simply went around the Wall. Like the Pyramids in Egypt, the Wall was more the ruling monarchy saying “look how big and important I am – I can order my fellow country men to build a large pile of stones, and even if hundreds of thousands of them die while building it (as in the case of the Wall), then well it’s too bad for them. I’m the Emperor. (Or Pharoh, as the case may be.
