Military conquests during the Han dynasty brought a number of foreign peoples within the Chinese empire when the Imperial Chinese tributary system began to evolve under Han rule. This tributary system was based on the Chinese worldview, that had developed under the Shang dynasty, in which China is deemed the center and apogee of culture and civilization, the "Middle kingdom" (Zhōngguó), surrounded by several layers of increasingly barbarous peoples. Contact with Southeast Asia steadily increased by the end of the Han period.