Ancient Migration: Wars and Walls

In 2020, nearly 376 million Chinese people did not live in the cities where they had registered their household information, up by more than 154 million in the 2010 census. This sounds a bit odd when it’s compared to the Chinese tradition of emotionally being attached to one’s homeland where one is born and lives on the land that you farm. 
In world history, flows of people, either in peaceful or violent ways, have always been both a big factor and a result of fundamental social changes. For example, the Western Roman Empire fell due to incursions by Germanic tribes. 
Did ancient Chinese move en masse? If they did, why? And did their migration also result from and change the society at that time?