The Han Dynasty's Evolution of Defense and Strategy in the West of Yellow River

As the joint part of four political and economic regions of Mongolian Plateau,Tibetan Plateau,Central Plain,and Western Regions,the western regions of Yellow River played an invaluable role in military strategy in the Han Dynasty.In order to meet the need of political and geographical changes after occupation of these regions,the Han Dynasty's defense establishment in these regions experienced two stages of beginning and maturity.The Han Dynasty strengthened its defense measures by establishing four counties and tributaries,building fortresses of Juyan and Xiutu.It also adjusted its military strategy accordingly by making the army of these regions be the main force or auxiliary force to fight with other armies,which highlighted its military frontline position increasingly and became the inevitable path for the Han Dynasty to fight in the west and north.Taken the hundred war history between the Han Dynasty and Hun into consideration,it can be found that the Han Dynasty's evolution of defense and military strategy played an important role in it.Therefore,this paper attempts to investigate the Hun's fight for these regions,the Han Dynasty's defense measures and its evolution of attack and defense strategies as well,on the basis of which this paper analyzes its reasons from the perspective of geography.