Goguryeo frequently battled with the Gongsun clan despite initial cooperation. In 197, hostilities between the Gongsuns and Goguryeo first broke out when Balgi, elder brother of King Sansang of Goguryeo, staged a rebellion and gained the support of Gongsun Du. Sansang's younger brother Gyesu repelled the attack, defeating Gongsun Du, and Balgi committed suicide. Gongsun Kang took advantage of a succession feud in Goguryeo and launched an attack again in 209, defeating Goguryeo and forcing it to move its capital. In Sima Yi's conquest of Yan, Goguryeo sent thousands of troops to assist Sima Yi.