In 648, Kim Chunchu of Silla visited Emperor Taizong of the Tang to seek an alliance aimed at countering Baekje. During their meeting, they discussed concluding a military alliance between Silla and Tang, intending to subdue both Goguryeo and Baekje and then divide the territories. This plan was formalized in an imperial edict, which was sent to Silla. However, in 649, Emperor Taizong passed away, leaving a command to halt the assault on Goguryeo, causing the Tang court to pause its aggressive policy toward Goguryeo, and the Silla-Tang alliance was temporarily suspended. While Tang was responding passively to Goguryeo, the latter expanded its influence over the Khitan territory controlled by Tang, intensifying pressure on Tang. As a result, around 654, military clashes erupted in the eastern Mongolian region, reigniting tensions between Tang and Goguryeo. Seizing this opportunity, Silla, under King Muyeol, renewed its request to Tang for an alliance, which Emperor Gaozong approved, finally concluding the Silla-Tang military alliance as both kingdoms’ interests aligned.