In some Chinese sources, Go Anseung is recorded as the grandson of Bojang, the last king of the ancient Korean kingdom of Goguryeo.
Anseung was crowned ruler of the new Goguryeo, centered in the city of Hansung, in today's South Hwanghae province, North Korea.
In the eighth month of 670, King Munmu of Silla sent a royal decree to Anseung, reading in part: Now people cannot be without a ruler and August Heaven must have one to entrust with the mandate.
You must gather together and calm your refugee peoples, continue old ties and give them new life, be as a neighbor state for all times and conduct affairs as brothers.
Shortly thereafter in 672, and under circumstances unknown but evidence of internal turmoil within the new kingdom, Geom was killed under Anseung's orders.