The wars of Tang and Tubo in the Inside-Shanhaiguan Roads lasted for nearly a hundred years

which make an important part of the military history of Tang dynasty.However

research focused on military systems and campaigns

the overall analysis of the battle process

campaign strategy

and tactics of the evolution were neglected.Layers defense system of the Tang dynasty in Inside-Shanhaiguan Roads controlled the battle process of Tubo

and so did the irrigation system and the supplies path of Lingzhou.At last

the lack of forage supplies destroyed the campaign strategy of Tubo to separate the land of Tang dynasty.