The Goguryeo–Tang War occurred from 645 to 668 and was initially fought between the Goguryeo kingdom and Tang Dynasty. During the course of the war the two sides allied with various other states. For the first decade and a half of the war, both sides were evenly matched, with Goguryeo successfully defending against the invading Tang army in what has become to be known as the first campaign in the Goguryeo–Tang War. After the fall of Baekje in 663, Tang and Silla armies started making headway. The following year, Tang forces invaded Goguryeo from the north and Silla from the south. In late 668, exhausted from numerous attacks, the kingdoms of Goguryeo and the remnants of Baekje army succumbed to numerically superior armies of the Tang Dynasty and Silla.