Anseung , alternately Ansun, was thought to be either the nephew or illegitimate son of King Bojang of Goguryeo, the last King ofGoguryeo. He was named the new King of Goguryeo by general Geom Mojam, but later he murdered Geom and submitted to the Korean kingdom of Silla, taking up residence in the Silla capital of Gyeongju.
Background
Go Anseung was the nephew of King Bojang of Goguryeo, and a prince of Goguryeo before its fall. In some Chinese sources, Go Anseung is recorded as the grandson of Bojang, the last king of the ancient Korean kingdom of Goguryeo.
Ruler of a rump Goguryeo
In 668, Prince Anseung was in Silla, where he had been held as hostage for many years. Upon hearing of his kingdom's defeat and downfall, he searched for survivors and first sought permission to revive his kingdom. Anseung encountered the high Goguryeo official Geom Mojam, also in flight. Together they forged an alliance to revive the Goguryeo kingdom. Anseung was crowned ruler of the new Goguryeo, centered in the city of Hansung, in today's South Hwanghae province, North Korea. Envoys were soon dispatched to Silla seeking a restitution of some territory for a revived Goguryeo kingdom as well as a defensive alliance with "the Great State". Silla, eager to break its ties with Tang, which following the defeat of Goguryeo and Baekje now threatened to impose its hegemony over the former Baekje and Goguryeo territories, agreed to reestablish, and ally with, a revived Goguryeo under king Anseung. In the eighth month of 670, King Munmu of Silla sent a royal decree to Anseung, reading in part: King Munmu then bestowed upon him the title of King of Bodeok, and bequeathed him a small piece of territory in the vicinity of what is today the city of Iksan near the former Baekje capital at Buyeo, ostensibly to serve as a roadblock to the expected Tang attempts to control that region.
The end of the Kingdom of Bodeok
The revived Goguryeo territory of Bodeok soon became a haven for remnants of the Goguryeo population. Shortly thereafter in 672, and under circumstances unknown but evidence of internal turmoil within the new kingdom, Geom was killed under Anseung's orders. In the third year of the reign of Silla’s King Sinmun, in the wake of rebellious plots by Silla aristocrats against King Sinmun, Silla abolished the small kingdom of Bodeok and Anseung was made to reside in the Silla capital of Gyeongju, where he was granted the official title of sopan, bestowed with the clan name of Kim, and given a generous piece of land and magnificent dwelling. The Kingdom of Bodeok came to an end and the remnant Goguryeo populace there was repopulated in various locales in the south. The date and circumstances of Anseung's death are unknown.