Tang-Tibet War (7th century)

Timeline

1. 638–641Songzhou · SichuanSongtsen Gampo sent envoys to seek a Tang marriage; Emperor Taizong agreed to Princess Wencheng, but Tibet, embroiled in a dispute over Tuyuhun, first attacked Songzhou; Tang forces under Hou Junji counterattacked and Tibet withdrew.
2. 641Lhasa · TibetPrincess Wencheng entered Tibet to marry Songtsen Gampo, bringing Central Plains culture, technology, and Buddhist influence; Tang-Tibet relations temporarily eased and both sides exchanged envoys.
3. 663–670Former Tuyuhun territory · QinghaiTibetan power continued expanding eastward, destroying Tuyuhun and occupying the Qinghai Plateau, forming a direct standoff with Tang in the Hehuang region and once again tensing relations.
4. 670Dafeichuan · QinghaiTang general Xue Rengui led over a hundred thousand troops against Tibet but was ambushed at Dafeichuan by the Tibetan general Gar Tongtsen Yulsung; the Tang army was badly defeated, some of the Four Garrisons of the Western Regions were lost, and a long-term standoff took shape.