Tibet was once a strong power contemporaneous with Tang China (618–907). Until the Tibetan Empire's collapse in <answer>the 9th century</answer>, it was the Tang's major rival in dominating Inner Asia. The Yarlung rulers of Tibet also signed various peace treaties with the Tang, culminating in a treaty in 821 that fixed the borders between Tibet and China.
In what century did the Tibetan Empire fall?
the 9th century