This research analyzes historical sources such as epitaphs and classical Chinese texts, to focus on political tendencies among both the nomadic tribes of the First Turkic Qaghanate and warlords in northern China in the late Sui to the early Tang dynasty. The analysis reveals that the Zhishi 執失, a powerful Turkic tribe, was split by allegiances to both the Qaghanate and the Tang, so that while Zhishi Sili 執失思力 played a key role as a chief vassal of Xieli Qaghan 頡利可汗, Sili's father, Zhishi Wu 執失武, formed a cavalry corps under Li Shimin 李世民. On the other hand, of the warlords that maintained spheres of influence in northern China, those with only relatively limited power, such as Zhang Changsun 張長遜, Guo Zihe 郭子和, and Wan Junzhang 苑君璋, swore their allegiance to both the Türks and the Tang at the same time. Both the Türks and the Tang felt it to be dangerous that these warlords pledged their allegiance to the other side, and sometimes carried out attacks or executions when they ascertained that this was the case. Conversely, there were also cases in which they encouraged the warlords to betray the other side. It is thought that both the Türk nomadic tribes and those warlords with minor spheres of influence sought to survive by shifting between both sides.