How did Taizong use diplomacy to weaken the western Turks?

To weaken the western Turks, Emperor Taizong employed a strategy of encouraging internal dissension among their leadership. By fostering these divisions, he successfully exploited the instability within the western khanates.1

Following this period of internal fragmentation, Taizong utilized diplomatic engagement to solidify Chinese influence. In 642–643, when a new khan emerged and reestablished a degree of unified control, Taizong provided Chinese support and secured the khan's agreement to become a tributary of the Tang dynasty. To formalize and seal this alliance, Taizong arranged for the khan to marry a Chinese princess. This combination of promoting internal conflict and establishing tributary relations allowed the Tang to effectively manage and diminish the threat posed by the western Turks.1