The Three Kingdoms Period was a violent era in which the three kingdoms of Paekche, Koguryo, and Silla fought for dominance over the Korean Peninsula from 57 to 668 AD. The Silla Kingdom in alliance with Tang China defeated the other two kingdoms and formed the United Silla Kingdom. Without Queen Seondeok, the Silla-Tang Alliance would not have been formed and the outcome of the Three Kingdoms Period would be drastically different.