Bojang of Goguryeo - Reign

Reign

Goguryeo continued battle against the southern Korean kingdom of Silla, in alliance with the third of the Three Kingdoms, Baekje. Silla was further isolated by Goguryeo's restored relations with the Wa of Japan. In 642, Silla sent Kim Chun-chu to negotiate a treaty, but when Yeon Gaesomun demanded the return of the Seoul region, talks broke down, leading Silla to eventually ally with the Tang Dynasty.

In 645, the Tang Taizong led a major expedition against Goguryeo by land and sea, but Yeon Gaesomun and Yang Manchun repelled the invasion, as well as subsequent smaller attacks by the Tang. In 654, Goguryeo attacked the Khitans, who were allied with the Tang. In 655, Goguryeo and Baekje attacked Silla.

The Baekje kingdom finally fell to Silla-Tang in 660. Yeon Gaesomun defeated major invasions of Pyongyang in 661 and Sasu River in 662, but Silla and Tang were now free to focus and intensify their attacks against Goguryeo. In 663, the Baekje revival movement ended as its leader Buyeo Pung retreated to Goguryeo.

After the death of Yeon Gaesomun in 666, Bojang was unable to gain control over the country, which instead was wracked by a succession struggle between Yeon's sons.