Yeon Gaesomun
In 660, Goguryeo's ally, Baekje, fell to the Silla–Tang alliance; the victorious allies continued their assault on Goguryeo for the next eight years but could not defeat Yeon Gaesomun. However, Yeon Gaesomun died of a natural cause and civil war ensued among his three sons, leading the Silla–Tang alliance to launch a fresh invasion. In November 668, King Bojang surrendered to the Silla–Tang alliance and Goguryeo finally fell.