As a frontier region of the Qin-Han (221BCE-220CE) empire, the northwest was a new territory to the Chinese realm. Until the Later Han (25-220CE) times, some portions of the northwestern region had only been part of imperial soil for one hundred years. Its coalescence into the Chinese empire was a product of long-term expansion and conquest, which arguably defined the region's military nature. Furthermore, in the harsh natural environment of the region, only tough people could survive, and unsurprisingly, the region fostered vigorous warriors. Mixed culture and multi-ethnicity featured prominently in this highly militarized frontier society, which contrasted sharply with the imperial center that promoted unified cultural values and stood in the way of a greater degree of transregional integration. As this project shows, it was the northwesterners who went through a process of political peripheralization during the Later Han times played a harbinger role of the disintegration of the empire and eventually led to the breakdown of the early imperial system in Chinese history. In this study, the author adopts a regional perspective by focusing on the role of the northwestern frontier region vis-Ã -vis the imperial center to explain the collapse of the Later Han empire. The author emphasizes the role that regional conflicts played in the decline and fall of the dynasty, and paid particular attention to the incompatibility between the militarized culture of the northwest and the civil values promoted by the imperial center, which was dominated by the eastern-based scholar-officials. Through this analysis, the author provides a case study of the relationship between the imperial center and the regions with different cultures and identities, and the variations of the conception of such a relationship in the period of early imperial China.