Question: why did they build the wall of china

title: History of the Great Wall of China
text: According to the model by sinologist Karl August Wittfogel , the loess soils of Shaanxi made it possible for the Chinese to develop irrigated agriculture early on . Although this allowed them to expand into the lower reaches of the Yellow River valley , such extensive waterworks on an ever - increasing scale required collective labour , something that could only be managed by some form of bureaucracy . Thus the scholar - bureaucrats came to the fore to keep track of the income and expenses of the granaries . Walled cities grew up around the granaries for reasons of defence along with ease of administration ; they kept invaders out and ensured that citizens remained within . These cities combined to become feudal states , which eventually united to become an empire . Likewise , according to this model , walls not only enveloped cities as time went by , but also lined the borders of the feudal states and eventually the whole Chinese empire to provide protection against raids from the agrarian northern steppes .