The Song Dynasty succeeded in reunifying several kingdoms.
The Song dynasty refers to an era of Chinese history that began in 960, directly after the chaotic Five Dynasties and Ten Kingdoms period.
The Song dynasty was divided into two distinct periods, Northern (960–1127) and Southern (1127–1279).
The Song Dynasty succeeded in uniting the kingdoms when the first emperor of their dynasty took the throne from himself. This meant the end of the famous "five dynasties and ten kingdoms" period in Chinese history ruling from 960 to 1279 with numerous emperors and a three time change in the capital of the empire.
Immigration policies refer to a national sphere because it affects the country as a whole, so all changes and the formulation process of an immigration policy must come from a national sphere and the whole country needs to live by these laws and policies.