Liaodong was adjacent to Goguryeo, whose rulers initially cooperated with Gongsun Du but subsequently frequently quarreled.

Though the candidate supported by Gongsun Kang was eventually defeated, the victor Sansang of Goguryeo was compelled to move his capital southeast to Hwando (present-day Ji'an, Jilin) on the Yalu River, which offered better protection.

Claiming that he would restore Liaodong to glory, he forced Gongsun Gong from the throne, imprisoned him and became ruler in December 228.

In February 230, Wei promoted Gongsun Yuan to cheqi general (Chinese: 車騎將軍; lit.

[21][22] In 237, Cao Wei general Guanqiu Jian sent troops to attack Gongsun Yuan, but was defeated because of heavy rain.

[23] After Guanqiu Jian's defeat, Gongsun Yuan claimed independence in July, and used the era date Shaohan (Chinese: 紹漢); the new country had a government and officials, and set up four commanderies: Liaodong, Xuantu, Lelang and Daifang, and in January 238, Gongsun Yuan resumed relations with Wu, hoping for military reinforcements from it.

[16][24] In June 238, after planning with Cao Rui, the Cao Wei general Sima Yi led 40,000 soldiers to attack Gongsun Yuan; after a siege lasting three months, Gongsun Yuan's headquarters fell to Sima Yi, who received assistance from Goguryeo.

[10][25] Sansang's younger brother Gyesu repelled the attack, defeating Gongsun Du, and Balgi committed suicide.

[29] After Wu's envoys were killed by Gongsun Yuan in 233, some of their troops escaped to Goguryeo and set up an Eastern Wu-Goguryeo alliance.

[32] The Cao Wei-Goguryeo alliance broke down in 242, when King Dongcheon of Goguryeo plundered the Liaodong district of Xi'anping (西安平; near present-day Dandong) at the mouth of the Yalu River.

[34] Although the King evaded capture and eventually settled in a new capital, Goguryeo was reduced to such insignificance that for half a century there was no mention of the state in Chinese historical texts.