Gung Ye Founds Later Goguryeo
Gung Ye, who had risen under the warlord Yanggil and taken Gangwon, Gyeonggi and Hwanghae, founded Later Goguryeo at Songak in 901.

Teego · CC BY-SA 4.0 · Source
Said to be of Silla royal blood, Gung Ye was a monk at Sedalsa before serving the warlords Gihwon and Yanggil. After taking Gangwon and much of Gyeonggi and Hwanghae and winning over the Wang family of Songak, he proclaimed Later Goguryeo at Songak in 901 as heir to Goguryeo.
He was bitterly hostile to Silla, which he called “the doomed capital”.