Why did the great migration in the south of the Yangtze River during the reign of Emperor Wu of the Han Dynasty reflect the strengthening of centralization?

Large-scale migration in the south of the Yangtze River during the period of Emperor Wu of Han Dynasty reflected the strengthening of centralization, because migration was a strategic measure vigorously promoted during the period of Emperor Wu of Han Dynasty to resist Xiongnu and defend the frontier, an auxiliary policy for Emperor Wu of Han Dynasty to solve wartime financial difficulties, and an important means to stabilize the feudal ruling order and consolidate centralization. This policy has been implemented for nearly 40 years, from the first migration of 100,000 people to Shuofang in the second year of Yuan Shuo (BC 127) to the fourth year of Zheng He (BC 89), when Emperor Wu of the Han Dynasty sent a letter to garrison troops. Its maintenance time is long, the number of immigrants is large, the scope of reclamation is wide, and the effect is remarkable, which is unprecedented.