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Silla–Tang alliance
648· Event· Rulers & states
Well documentedSolid records, physical evidence or scientific consensus.
The 648 pact in which Silla's envoy Kim Chun-chu and Tang Emperor Taizong agreed to destroy Baekje and Goguryeo together.
See it on the Korean History map →What happened
By 642 Silla was squeezed: Baekje had seized more than 40 of its fortresses, and Goguryeo had refused help and briefly detained Kim Chun-chu. In 648 he sailed to the Tang capital, Chang'an, and won Taizong's backing. Silla adopted Tang court dress in 649 and Tang's reign era in 650, signs of junior partnership. The alliance (나당동맹) paired Tang's huge armies with Silla's local knowledge, troops and supply lines.
Why it matters
It turned a three-way regional rivalry into a war Silla could win, but also invited Tang ambitions to rule the whole peninsula.
Think of it like
Like a small local owner bringing in a big outside partner to win a deal, then fighting that partner over control.
How we know
Recorded in the Samguk sagi and in Chinese sources such as the Old Book of Tang.
Still debated
Silla later claimed Taizong promised it the land south of Pyongyang; that promise is known only from King Munmu's 671 letter to a Tang general.
Connections (3)
▸Silla–Tang alliance led to Fall of BaekjeWell documented
The connection
The alliance's first target was Baekje, Silla's nearest enemy. In 660 Tang sent about 130,000 men across the Yellow Sea to the Geum River, timed to meet Silla's army marching overland. Caught between them, Baekje collapsed in about ten days.
When and how
660; Tang under Su Dingfang, Silla under King Muyeol and Kim Yu-sin, converging on Baekje's capital, Sabi.
How we know
Korean, Chinese and Japanese sources all describe the joint campaign; Su Dingfang's victory inscription survives on Buyeo's Jeongnimsa pagoda.
Debates and open questions
Why the allies struck Baekje before Goguryeo is debated: as the easier target, to cut Goguryeo's ally, or to satisfy Silla first.
▸Silla–Tang alliance was negotiated by King Taejong Muyeol (Kim Chun-chu)Well documented
The connection
Before he became king, Kim Chun-chu made the alliance in person. After failing to win Goguryeo's help in 642, he traveled to Chang'an in 648, impressed Taizong and left a son at the Tang court as a pledge. The pact then helped carry him to the throne.
When and how
648, at the Tang capital Chang'an, between Kim Chun-chu and Emperor Taizong, while Queen Jindeok ruled Silla.
How we know
The Samguk sagi and the Old and New Tang histories record his visit and Taizong's favor.
Debates and open questions
What exactly was agreed, especially on territory, survives only in Silla's later telling.
▸Silla–Tang alliance led to Fall of GoguryeoWell documented
The connection
With Baekje gone, the allies turned north. Tang supplied the main armies; Silla sent troops and grain and attacked from the south. A Goguryeo succession feud after Yeon Gaesomun's death finally let the combined pressure break Pyongyang in 668.
When and how
661–668: failed sieges in 661–662, then the final campaign of 667–668 under Tang's Li Ji and Silla's King Munmu.
How we know
The Samguk sagi records Silla troops and grain convoys, including Kim Yu-sin's winter supply march of 662; Tang histories record the campaigns.
Debates and open questions
How much Silla's role mattered, compared with Tang power and Goguryeo's internal split, is debated.