What was the geostrategic situation in ancient China?

The scenes of China's ancient history activities are mainly in the Yellow River basin, with the forces in the upper reaches of the west dominating and the cultural economy in the lower reaches of the east dominating. For example, when the Western Han Dynasty made Guanzhong its capital in history, "Chang 'an was the first in the country, and the culture and economy of the East were continuously transported to the west, blending with the western forces, and then extending from Chang 'an to the northwest, such as expelling the Huns and opening up the western regions. The posture of establishing a country in the Western Han Dynasty is often coordinated, dynamic and enterprising. It was through the strategic measures of emigrating to Guanzhong and Northwest China that the Western Han Empire coordinated the economic center and the political center. On the one hand, it defended the political center of the empire, on the other hand, the border counties close to the political center became reliable strategic bases for operating the northern and northwest frontiers. On the contrary, the Eastern Han Dynasty, with Luoyang as its capital, did not focus on Guanzhong and Longyou. In this way, the desolation of border counties directly affected the border security of the Eastern Han Dynasty, and it was difficult for the Eastern Han Dynasty to make great achievements in border management.