东汉末年复杂多变的形势使得东吴略取益州的战略未能顺利实行,为了减轻上游威胁、抗衡曹魏势力,东吴转而积极谋求“西土之援”。其经营的“西土之援”一定程度上保障了国土西部的防御安全,造成了“合东西之势进图北方”的有利态势。然而因为敌我关系的多变,“西土之援”并不稳固,存在着“合东西之势”作用的有限性和“籍外交而不能固”的问题。 The complex and volatile situation in the late Eastern Han dynasty made Soochow’s strategy of taking Yizhou slightly unmanaged, and in order to reduce the threat from the upper reaches and counter the forces of Cao Wei, Soochow turned actively to seek “aid from the west.” The “Aid for Western Territories” operated by the company guaranteed the defensive security of the western part of the country to a certain extent, resulting in a favorable situation of “combining the east-west trend into the northern part of the map ”. However, due to the changing relations between the enemy and ourselves, the “assistance from the West soil” is not stable and there exists the limitation of the role of “combining things with one another” and the problem of “diplomacy but not solidarity”.